U.S. patent application number 11/730141 was filed with the patent office on 2007-10-04 for polishing method and polishing apparatus.
Invention is credited to Akira Fukuda, Hirokuni Hiyama, Manabu Tsujimura.
Application Number | 20070232203 11/730141 |
Document ID | / |
Family ID | 38559806 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070232203 |
Kind Code |
A1 |
Fukuda; Akira ; et
al. |
October 4, 2007 |
Polishing method and polishing apparatus
Abstract
A polishing method can prevent scratches in a polished surface
of a polishing object, caused by foreign matter adhering to a
surface of a polishing member, thus preventing the attendant
lowering of the yield even when the polishing object is
large-sized. The polishing method includes: specifying a foreign
matter adhesion position or a foreign matter adhesion area in a
surface of the polishing member; and intensively cleaning the
foreign matter adhesion position or the foreign matter adhesion
area in the surface of the polishing member.
Inventors: |
Fukuda; Akira;
(Kanagawa-ken, JP) ; Hiyama; Hirokuni;
(Kanagawa-ken, JP) ; Tsujimura; Manabu; (Tokyo,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W., SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
38559806 |
Appl. No.: |
11/730141 |
Filed: |
March 29, 2007 |
Current U.S.
Class: |
451/287 ;
451/444; 451/5 |
Current CPC
Class: |
B08B 1/04 20130101; H01L
21/67219 20130101; B08B 3/02 20130101; B24B 53/017 20130101 |
Class at
Publication: |
451/56 ; 451/5;
451/444 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2006 |
JP |
2006-092159 |
Jan 22, 2007 |
JP |
2007-011962 |
Claims
1. A polishing method for polishing a polishing object by applying
pressure between a polishing member and the polishing object while
moving the polishing member and the polishing object relative to
each other, comprising: specifying a foreign matter adhesion
position or a foreign matter adhesion area in a surface of the
polishing member; and intensively cleaning the foreign matter
adhesion position or the foreign matter adhesion area in the
surface of the polishing member.
2. A polishing method for polishing a polishing object by applying
pressure between a polishing member and the polishing object while
moving the polishing member and the polishing object relative to
each other, comprising: reading information on an intensive
cleaning position or an intensive cleaning area in a surface of the
polishing member from a storage medium in a computer; and
intensively cleaning the intensive cleaning position or the
intensive cleaning area in the surface of the polishing member.
3. A polishing method for polishing a polishing object by applying
pressure between a polishing member and the polishing object while
moving the polishing member and the polishing object relative to
each other, comprising: reading information on an intensive
cleaning position or an intensive cleaning area in a surface of the
polishing member from a storage medium in a computer; specifying a
foreign matter adhesion position or a foreign matter adhesion area
in the surface of the polishing member; and intensively cleaning at
least one of the intensive cleaning position or the intensive
cleaning area in the surface of the polishing member and the
foreign matter adhesion position or the foreign matter adhesion
area in the surface of the polishing member.
4. A polishing method for polishing a polishing object by applying
pressure between a polishing member and the polishing object while
moving the polishing member and the polishing object relative to
each other, comprising: specifying a foreign matter adhesion
position or a foreign matter adhesion area in a surface of the
polishing member; storing foreign matter adhesion positions or
foreign matter adhesion areas in the surface of the polishing
member; calculating an intensive cleaning position or an intensive
cleaning area in the surface of the polishing member from the
stored foreign matter adhesion positions or foreign matter adhesion
areas; and intensively cleaning at one of the calculated intensive
cleaning position or foreign matter adhesion area in the surface of
the polishing member and the specified foreign matter adhesion
position or foreign matter adhesion area in the surface of the
polishing member.
5. The polishing method according to claim 1, wherein adhesion of
foreign matter to the surface of the polishing member is detected
by a detection section to specify the foreign matter adhesion
position or the foreign matter adhesion area in the surface of the
polishing member.
6. The polishing method according to claim 5, wherein the detection
of adhesion of foreign matter to the surface of the polishing
member is performed by image analysis of the surface.
7. The polishing method according to claim 3, wherein adhesion of
foreign matter to the surface of the polishing member is detected
by a detection section to specify the foreign matter adhesion
position or the foreign matter adhesion area in the surface of the
polishing member.
8. The polishing method according to claim 7, wherein the detection
of adhesion of foreign matter to the surface of the polishing
member is performed by image analysis of the surface.
9. The polishing method according to claim 4, wherein adhesion of
foreign matter to the surface of the polishing member is detected
by a detection section to specify the foreign matter adhesion
position or the foreign matter adhesion area in the surface of the
polishing member.
10. The polishing method according to claim 9, wherein the
detection of adhesion of foreign matter to the surface of the
polishing member is performed by image analysis of the surface.
11. The polishing method according to claim 1, wherein the polished
surface of the polishing object after polishing is evaluated to
specify the foreign matter adhesion position or the foreign matter
adhesion area in the surface of the polishing member.
12. The polishing method according to claim 11, wherein the
evaluation of the polished surface of the polishing object after
polishing is performed by image analysis of the polished
surface.
13. The polishing method according to claim 3, wherein the polished
surface of the polishing object after polishing is evaluated to
specify the foreign matter adhesion position or the foreign matter
adhesion area in the surface of the polishing member.
14. The polishing method according to claim 13, wherein the
evaluation of the polished surface of the polishing object after
polishing is performed by image analysis of the polished
surface.
15. The polishing method according to claim 4, wherein the polished
surface of the polishing object after polishing is evaluated to
specify the foreign matter adhesion position or the foreign matter
adhesion area in the surface of the polishing member.
16. The polishing method according to claim 15, wherein the
evaluation of the polished surface of the polishing object after
polishing is performed by image analysis of the polished
surface.
17. A method for specifying a cleaning region in a surface of a
polishing member, comprising: evaluating the surface of the
polishing member to specify a foreign matter adhesion position or a
foreign matter adhesion area in the surface of the polishing member
as a position or area to be intensively cleaned; and storing the
specified intensive cleaning position or intensive cleaning
area.
18. A method for specifying a cleaning region in a surface of a
polishing member, comprising polishing a polishing object by
applying pressure between a polishing member and the polishing
object while moving the polishing member and the polishing object
relative to each other, and evaluating a polished surface of the
polishing object to specify a foreign matter adhesion position or a
foreign matter adhesion area in the surface of the polishing member
as a position or area to be intensively cleaned.
19. The method according to claim 18, wherein information on the
specified foreign matter adhesion position or foreign matter
adhesion area in the surface of the polishing member is stored.
20. The method according to claim 18, wherein the evaluation of the
polished surface of the polishing object is performed by image
analysis of the polished surface.
21. A method for specifying a foreign matter adhesion region,
comprising specifying a foreign matter adhesion position or a
foreign matter adhesion area in a surface of a polishing member by
image analysis of a shot image of a polished surface of a polishing
object.
22-75. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing method and a
polishing apparatus for polishing optical components, machine
components, ceramics, metals, etc., a program for carrying out the
polishing method, and a storage medium storing the program, and
more particularly to a polishing method and a polishing apparatus
which are suitable for polishing a polishing object, such as a
semiconductor wafer, into a flat mirror-like surface, a program for
carrying out the polishing method, and a storage medium storing the
program.
[0003] 2. Description of the Related Art
[0004] With the recent progress toward higher integration of
semiconductor devices, circuit interconnects are becoming finer and
the sizes of devices integrated are becoming smaller. The
manufacturing of such semiconductor devices necessitate a process
of removing by polishing a film formed in a surface of a
semiconductor wafer, thereby flattening the surface. There are
various methods for performing such a wafer flattening process,
among which is polishing by chemical mechanical polishing (CMP)
apparatus. A chemical mechanical polishing apparatus includes a
polishing member (polishing cloth, polishing pad, etc.) and a
holder (top ring, polishing head, chucks, etc.) for holding a
polishing object, such as a semiconductor water. During polishing
of a polishing object, a surface (to be polished) of the polishing
object is pressed against a surface of the polishing member while
moving them relative to each other, and a polishing aid (abrasive
liquid, chemical, slurry, pure water, etc.) is supplied
therebetween, thereby polishing the surface of the polishing object
into a flat mirror-like surface. Polishing by a chemical mechanical
polishing apparatus is known to perform good polishing by the
combination of chemical polishing action and mechanical polishing
action.
[0005] A foamed resin or a non-woven fabric is generally used as a
material for a polishing member for use in a chemical mechanical
polishing apparatus. Such a polishing member has fine surface
irregularities, which act as chip pockets effective for prevention
of clogging and a reduction in polishing resistance. The fine
surface irregularities, however, smooth down during continued
polishing of a polishing object with the polishing member, causing
a decrease in the polishing rate. It is therefore necessary to
carry out dressing of the surface of the polishing member, for
example, by using a diamond dresser with a large number of diamond
particles electrodeposited on its surface, to re-create fine
irregularities in the surface of the polishing member.
[0006] During the dressing, the diamond particles can fall from the
dresser and dressing debris can be produced. The diamond particles,
which have fallen from the dresser, and the dressing debris are
usually removed from the surface of the polishing member by a
cleaning liquid which is supplied upon dressing. If, however, some
of them are not removed and remain on the surface of the polishing
member, they may form foreign matter and the foreign matter can
cause a scratch or scratches in a surface (polished surface) of a
polishing object after polishing.
[0007] Besides such diamond particles and dressing debris produced
during dressing, debris of a film and debris of the polishing
member, produced upon polishing of a film, such as an oxide film or
a metal film, abrasive grains contained in a polishing aid, etc.
can agglomerate into foreign matter and adhere to the surface of
the polishing member, and such foreign matter can also cause a
scratch or scratches in the polished surface of the polishing
object. When the polishing object is a semiconductor wafer, such
scratches are highly likely to be fetal defects, causing serious
problems. Further, if polishing is continued with the polishing
member with foreign matter adhering to the surface, production of
scratches will continue not only on one polishing object but on a
plurality of polishing objects until the foreign matter is removed
from the surface of the polishing member, resulting in a lowering
of the yield.
[0008] As described above, scratches formed in the surface of a
polishing object are likely to be fetal detects. For the purpose of
preventing scratches, various methods and apparatuses have been
proposed to remove foreign matter adhering to a surface of a
polishing member. For example, a method has been proposed in which
a cleaning liquid, such as pure water or a liquid chemical, is
blown onto a polishing member to clean off foreign matter from the
polishing member, and a polishing apparatus incorporating an
apparatus for carrying out the method has also been proposed (see
Japanese Patent Laid-Open Publication Nos. H10-94964, H10-244458,
H10-296625, H11-243072, H11-333695, 2000-218517, 2000-280163,
2000-340531 and 2001-144055). A method has been proposed in which
foreign matter is removed from a surface of a polishing member by
blowing a cleaning liquid onto the polishing member while rubbing
the surface of the polishing member with a brush, a grindstone, a
PVA sponge, or the like, and a polishing apparatus provided with an
apparatus for carrying out the method has also been proposed (see
Japanese Patent Laid-Open Publication Nos. H10-244458, H10-296625,
H11-333695, 2000-218517 and 2000-280163). A polishing apparatus has
been proposed in which an apparatus for sucking in a slurry is
provided so that a slurry, which is a cause of foreign matter, is
removed by suction from a surface of a polishing member (see
Japanese Patent Laid-Open Publication No. H10-94964). A polishing
apparatus has been proposed which is provided with a fluid bath for
cleaning a polishing member during polishing (see Japanese Patent
Laid-Open Publication No. H10-296625). A method has also been
proposed which involves dissolving foreign matter with a solvent,
such as peroxosulfuric acid or hydrofluoric acid, and a polishing
apparatus provided with an apparatus for carrying out the method
has also been proposed (see Japanese Patent Laid-Open Publication
Nos. H10-217104 and 2000-280163).
[0009] Further, a scratch analysis method and a scratch analysis
apparatus have been proposed which, in order to improve polishing
conditions which will cause scratches or improve a polishing
apparatus itself, analyze scratches formed in a surface (polished
surface) of a polishing object after polishing and specify a
polishing apparatus and its polishing conditions which have caused
scratches, and specify the position of foreign matter adhering to a
polishing member (see Japanese Patent Laid-Open Publication No.
2004-259871).
SUMMARY OF THE INVENTION
[0010] It is, however, difficult to completely remove foreign
matter adhering to a polishing member so as to fully prevent
scratches producing in a surface (polished surface) of a polishing
object after polishing. This is partly because, with the trend
toward larger-sized polishing objects, an area of a polishing
member for contact with a surface (to be polished) of a polishing
object becomes larger, whereby blowing of a cleaning liquid onto
the polishing member, rubbing of the polishing member with a brush,
etc. are likely to be uneven, making effective removal of foreign
matter from the polishing member difficult. On the other hand,
uniform cleaning of a surface of a polishing member, if possible,
may result in a failure in intensively cleaning a foreign matter
adhesion portion of the polishing member, leading to insufficient
removal of foreign matter from the polishing member.
[0011] The scratch analysis method and the scratch analysis
apparatus, disclosed in Japanese Patent Laid-Open Publication No.
2004-259871, are not cooperative with a polishing apparatus. The
analysis method and apparatus are therefore considered not to be
capable of promptly dealing with the occurrence of scratches in a
surface of a polishing object in a polishing apparatus operating in
a mass production line. Prevention of the lowering of the yield
will thus not be possible.
[0012] The present invention has been made in view of the above
situation in the related art. It is therefore an object of the
present invention to provide a polishing method and a polishing
apparatus which can prevent scratches in a polished surface of a
polishing object, caused by foreign matter adhering to a surface of
a polishing member, thus preventing the attendant lowering of the
yield even when the polishing object is large-sized, an adhesion
region specifying method and an adhesion region specifying
apparatus for specifying a foreign matter adhesion region, a
program for carrying out the polishing method and a program for
carrying out the adhesion region specifying method, and storage
media storing the programs.
[0013] In order to achieve the above object, the present invention
provides a polishing method for polishing a polishing object by
applying pressure between a polishing member and the polishing
object while moving the polishing member and the polishing object
relative to each other, comprising specifying a foreign matter
adhesion position or a foreign matter adhesion area in a surface of
the polishing member; and intensively cleaning the foreign matter
adhesion position or the foreign matter adhesion area in the
surface of the polishing member.
[0014] By intensively cleaning a foreign matter adhesion position
or a foreign matter adhesion area in the surface of the polishing
member, for example, after stopping polishing, foreign matter can
be effectively removed from the surface of the polishing
member.
[0015] The present invention also provides another polishing method
for polishing a polishing object by applying pressure between a
polishing member and the polishing object while moving the
polishing member and the polishing object relative to each other,
comprising: reading information on an intensive cleaning position
or an intensive cleaning area in a surface of the polishing member
from a storage medium in a computer; and intensively cleaning the
intensive cleaning position or the intensive cleaning area in the
surface of the polishing member.
[0016] By storing information on an intensive cleaning position or
an intensive cleaning area, which is a position or area of high
frequency of adhesion of foreign matter or a position or area which
is especially important to the polishing yield, adhesion of foreign
matter to a surface of a polishing member, which would cause
scratches on a polishing object, can be prevented.
[0017] The present invention also provides still another polishing
method for polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, comprising: reading information on an intensive cleaning
position or an intensive cleaning area in a surface of the
polishing member from a storage medium in a computer; specifying a
foreign matter adhesion position or a foreign matter adhesion area
in the surface of the polishing member; and intensively cleaning at
least one of the intensive cleaning position or the intensive
cleaning area in the surface of the polishing member and the
foreign matter adhesion position or the foreign matter adhesion
area in the surface of the polishing member.
[0018] When foreign matter is not detected on a surface of a
polishing member, e.g., during polishing and thus a foreign matter
adhesion position or a foreign matter-adhesion area is not
specified in the surface of the polishing member, an intensive
cleaning position or an intensive cleaning area will be intensively
cleaned. When foreign matter is detected on the surface of the
polishing member, the foreign matter adhesion position or the
foreign matter adhesion area will be intensively cleaned. Adhesion
of foreign matter to the surface of the polishing member can thus
be effectively prevented, and removal of foreign matter adhering to
the surface can be performed effectively. It is also possible to
intensively clean a wider area, including a foreign matter adhesion
position or a foreign matter adhesion area.
[0019] The present invention also provides still another polishing
method for polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, comprising: specifying a foreign matter adhesion position or
a foreign matter adhesion area in a surface of the polishing
member; storing foreign matter adhesion positions or foreign matter
adhesion areas in the surface of the polishing member; calculating
an intensive cleaning position or an intensive cleaning area in the
surface of the polishing member from the stored foreign matter
adhesion positions or foreign matter adhesion areas; and
intensively cleaning at one of the calculated intensive cleaning
position or foreign matter adhesion area in the surface of the
polishing member and the specified foreign matter adhesion position
or foreign matter adhesion area in the surface of the polishing
member.
[0020] This makes it possible to calculate, from stored data on
foreign matter adhesion positions or foreign matter adhesion areas
in a surface of a polishing member, a position or area, which is of
high frequency of adhesion of foreign matter, in the surface of the
polishing member and to store the calculated position or area as an
intensive cleaning position or an intensive cleaning area in a
storage medium. The longer the polishing time is, the more is the
amount of stored information on foreign matter adhesion positions
or foreign matter adhesion areas in the surface of a polishing
member, and thus the higher is the accuracy of intensive cleaning
position or intensive cleaning area. Accordingly, an operation for
removal of foreign matter from a surface of a polishing member can
be performed more effectively, and cleaning for prevention of
adhesion of foreign matter to the surface of the polishing member
can be performed more effectively.
[0021] Preferably, adhesion of foreign matter to the surface of the
polishing member is detected by a detection section to specify the
foreign matter adhesion position or the foreign matter adhesion
area in the surface of the polishing member.
[0022] By detecting adhesion of foreign matter to a surface of a
polishing member by the detection section, polishing can be stopped
immediately after detection of the foreign matter. After stopping
polishing, the surface of the polishing member may be cleaned to
remove the foreign matter, or the polishing member may be replaced
with a new one, thereby preventing scratches in a polished surface
of a polishing object. Especially by detecting foreign matter on
the surface of the polishing member by a contact method, foreign
matter on the surface of the polishing member can be detection with
high precision even when a liquid film or the like is present on
the surface of the polishing member.
[0023] The detection of adhesion of foreign matter to the surface
of the polishing member may be performed by image analysis of the
surface.
[0024] According to this method, there is no fear of contamination
of the polishing member by the detection section.
[0025] The polished surface of the polishing object after polishing
may be evaluated to specify the foreign matter adhesion position or
the foreign matter adhesion area in the surface of the polishing
member.
[0026] There is a correlation between a scratch formed in a surface
(polished surface) of a polishing object after polishing and a
foreign matter adhesion position or a foreign matter adhesion area
in a surface of a polishing member. Accordingly, by evaluating the
surface of the polishing object after polishing and detecting a
scratch formed in the surface, a foreign matter adhesion position
or a foreign matter adhesion area can be specified from the
position of the scratch. Therefore, by intensively cleaning the
foreign matter adhesion position or the foreign matter adhesion
area, foreign matter can be removed effectively.
[0027] The evaluation of the polished surface of the polishing
object after polishing can be performed by image analysis of the
polished surface.
[0028] For example, a check is made as to whether scratches in a
surface (polished surface) of a polishing object after polishing,
caused by foreign matter, are fetal defects or not, and only
scratches that are fetal detects are extracted. The extracted
scratches can specify those foreign matter adhesion positions or
foreign matter adhesion areas in a surface of a polishing member
which will cause fetal scratches. Polishing may be stopped
immediately after detection of the fetal scratches and intensive
cleaning may be carried out on the specified foreign matter
adhesion positions or foreign matter adhesion areas in the surface
of the polishing member. This can prevent the lowering of the
yield.
[0029] The present invention also provides a method for specifying
a cleaning region in a surface of a polishing member, comprising:
evaluating the surface of the polishing member to specify a foreign
matter adhesion position or a foreign matter adhesion area in the
surface of the polishing member as a position or area to be
intensively cleaned; and storing the specified intensive cleaning
position or intensive cleaning area.
[0030] The present invention also provides another method for
specifying a cleaning region in a surface of a polishing member,
comprising polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, and evaluating a polished surface of the polishing object to
specify a foreign matter adhesion position or a foreign matter
adhesion area in the surface of the polishing member as a position
or area to be intensively cleaned.
[0031] Preferably, information on the specified foreign matter
adhesion position or foreign matter adhesion area in the surface of
the polishing member is stored.
[0032] The evaluation of the polished surface of the polishing
object may be performed by image analysis of the polished
surface.
[0033] By thus storing the information on the specified position or
area, the stored information can be utilized for calculation of an
intensive cleaning position or an intensive cleaning area.
[0034] The present invention also provides a method for specifying
a foreign matter adhesion region, comprising specifying a foreign
matter adhesion position or a foreign matter adhesion area in a
surface of a polishing member by image analysis of a shot image of
a polished surface of a polishing object.
[0035] For example, when scratches are formed in a polished surface
of a polishing object, a foreign matter adhesion position or a
foreign matter adhesion area in a surface of a polishing member can
be specified by image analysis of a shot image of the polished
surface, enabling efficient removal of foreign matter from the
surface of the polishing member.
[0036] The present invention also provides a polishing apparatus
for polishing a polishing object by applying pressure between a
polishing member and the polishing object while moving the
polishing member and the polishing object relative to each other,
comprising: an adhesion region specifying section for specifying a
foreign matter adhesion position or a foreign matter adhesion area
in a surface of the polishing member; and a cleaning section for
intensively cleaning the foreign matter adhesion position or the
foreign matter adhesion area in the surface of the polishing
member, specified by the adhesion region specifying section.
[0037] By intensively cleaning a foreign matter adhesion position
or a foreign matter adhesion area in the surface of the polishing
member, for example, after stopping polishing, foreign matter can
be effectively removed from the surface of the polishing
member.
[0038] The present invention also provides another polishing
apparatus for polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, comprising: a cleaning section for cleaning a surface of the
polishing member; and a control section for reading information
from a storage medium storing information on an intensive cleaning
position or an intensive cleaning area in the surface of the
cleaning member, and so controlling the cleaning section as to
intensively clean the intensive cleaning position or the intensive
cleaning area in the surface of the polishing member.
[0039] This can prevent foreign matter from adhering to the surface
of the polishing member that would cause scratches.
[0040] The present invention also provides still another polishing
apparatus for polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, comprising: a cleaning section for cleaning a surface of the
polishing member; an adhesion region specifying section for
specifying a foreign matter adhesion position or a foreign matter
adhesion area in the surface of the polishing member; and a control
section for reading information from a storage medium storing
information on an intensive cleaning position or an intensive
cleaning area in the surface of the cleaning member, and so
controlling the cleaning section as to intensively clean at least
one of the read intensive cleaning position or intensive cleaning
area in the surface of the polishing member and the foreign matter
adhesion position or the foreign matter adhesion area in the
surface of the polishing member, specified by the adhesion region
specifying section.
[0041] When foreign matter is not detected on a surface of a
polishing member, e.g., during polishing and thus a foreign matter
adhesion position or a foreign matter adhesion area is not
specified in a surface of a polishing member, an intensive cleaning
position or an intensive cleaning area will be intensively cleaned.
When foreign matter is detected on the surface of the polishing
member, the foreign matter adhesion position or the foreign matter
adhesion area will be intensively cleaned. Adhesion of foreign
matter to the surface of the polishing member can thus be
effectively prevented, and removal of foreign matter adhering to
the surface can be performed effectively.
[0042] The present invention also provides still another polishing
apparatus for polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, comprising: a cleaning section for cleaning a surface of the
polishing member; an adhesion region specifying section for
specifying a foreign matter adhesion position or a foreign matter
adhesion area in the surface of the polishing member; and a control
section for storing foreign mater adhesion positions or foreign
matter adhesion areas in the surface of the polishing member,
specified by the adhesion region specifying section, calculating an
intensive cleaning position or an intensive cleaning area in the
surface of the polishing member based on the stored foreign matter
adhesion positions or foreign matter adhesion areas, and so
controlling the cleaning section as to intensively clean at least
one of the calculated intensive cleaning position or intensive
cleaning area in the surface of the polishing member and the
foreign matter adhesion position or the foreign matter adhesion
area in the surface of the polishing member, specified by the
adhesion region specifying section.
[0043] This makes it possible to calculate, from stored data on
foreign matter adhesion positions or foreign matter adhesion areas
in a surface of a polishing member, a position or area, which is of
high frequency of adhesion of foreign matter, in the surface of the
polishing member and to store the position or area as an intensive
cleaning position or an intensive cleaning area in a storage
medium. The longer the polishing time is, the more is the amount of
stored information on foreign matter adhesion positions or foreign
matter adhesion areas in the surface of a polishing member, and
thus the higher is the accuracy of the intensive cleaning position
or intensive cleaning area. Accordingly, an operation for removal
of foreign matter from a surface of a polishing member can be
performed more effectively, and cleaning for prevention of adhesion
of foreign matter to the surface of the polishing member can be
performed more effectively. Data on a foreign matter adhesion
position or a foreign matter adhesion area in a surface of a
polishing member, stored in the present polishing apparatus, or
data on an intensive cleaning position or an intensive cleaning
area in the surface of the polishing member, the latter data being
calculated from the former data, can be used in another polishing
apparatus. For example, in the case of installing a new polishing
apparatus in addition to an existing polishing apparatus, data
stored in the existing apparatus can be used in the new polishing
apparatus, whereby adhesion of foreign matter to the same type of
polishing member can be effectively prevented also in the new
apparatus.
[0044] In a preferred aspect of the present invention, the adhesion
region specifying section includes a detection section for
detecting foreign matter adhering to the surface of the polishing
member to specify the foreign matter adhesion position or the
foreign matter adhesion area in the surface of the polishing
member.
[0045] This makes it possible to take action, such as stopping
polishing, when the detection section has detected adhesion of
foreign matter to a surface of a polishing member. Especially by
providing the detection section in a polishing section, adhesion of
foreign matter to a surface of a polishing member can be promptly
detected. When a contact method is employed for detection of
foreign matter on a surface of a polishing member, the detection
can be performed with high precision even when there is a liquid
film or the like on the surface of the polishing member.
[0046] The adhesion region specifying section may include an image
analyzer for performing image analysis of the surface of the
polishing member to detect foreign matter adhering to the
surface.
[0047] This can prevent contamination of a polishing member, etc.
by the detection section.
[0048] In a preferred aspect of the present invention, the adhesion
region specifying section includes an evaluation device for
evaluating the polished surface of the polishing object after
polishing to specify the foreign matter adhesion position or the
foreign matter adhesion area in the surface of the polishing
member.
[0049] There is a correlation between a scratch formed in a surface
(polished surface) of a polishing object after polishing and a
foreign matter adhesion position or a foreign matter adhesion area
in the surface of a polishing member. Accordingly, by evaluating
the surface of the polishing object after polishing and detecting a
scratch formed in the surface, a foreign matter adhesion position
or a foreign matter adhesion area can be specified from the
position of the scratch. Therefore, by intensively cleaning the
foreign matter adhesion position or the foreign matter adhesion
area, foreign matter can be removed effectively.
[0050] The evaluation device is, for example, an image analyzer for
analyzing an image of the polished surface of the polishing object
after polishing to evaluate the surface.
[0051] For example, a check is made as to whether scratches in a
surface (polished surface) of a polishing object after polishing,
caused by foreign matter, are fetal defects or not, and only
scratches that are fetal detects are extracted. The extracted
scratches can specify those foreign matter adhesion positions or
foreign matter adhesion areas in the surface of a polishing member
which will cause fetal scratches. Polishing may be stopped
immediately after detection of the fetal scratches and intensive
cleaning may be carried out on the specified foreign matter
adhesion positions or foreign matter adhesion areas in the surface
of the polishing member. This can prevent the lowering of the
yield.
[0052] In a preferred aspect of the present invention, the control
section stores information on the foreign matter adhesion position
or the foreign matter adhesion area specified by the adhesion
region specifying section.
[0053] This makes it possible to utilize the stored information for
calculation of an intensive cleaning position or an intensive
cleaning area.
[0054] The present invention also provides an apparatus for
specifying a foreign matter adhesion position or a foreign matter
adhesion area in a surface of a polishing member, comprising; a
reading device for reading standard patterns from a storage medium;
a reading device for reading a shot image of a polished surface of
a polishing object; an arithmetic unit for performing image
analysis using the read standard patterns and the read image to
specify a foreign matter adhesion position or a foreign matter
adhesion area in the surface of the polishing member; and an output
device for outputting the foreign matter adhesion position or the
foreign matter adhesion area specified by the arithmetic unit.
[0055] When scratches are formed in a polished surface of a
polishing object, a foreign matter adhesion position or a foreign
matter adhesion area in a surface of a polishing member can be
specified by image analysis using prepared standard patterns and a
shot image of the polished surface of the polishing object.
Therefore, an operation for removing foreign matter from the
surface of the polishing member can be effectively performed. The
reading device for reading standard patterns and the reading device
for reading a shot image may, of course, comprise a common device
having the both functions.
[0056] The present invention also provides another apparatus for
specifying a foreign matter adhesion position or a foreign matter
adhesion area in a surface of a polishing member, comprising: a
reading device for reading geometric parameters of a polishing
apparatus and polishing conditions for polishing a polishing
object; a standard pattern production device for producing standard
patterns using the read geometric parameters and the read polishing
conditions; a reading device for reading a shot image of a polished
surface of the polishing object; an arithmetic unit for performing
image analysis using the produced standard patterns and the read
image to specify a foreign matter adhesion position or a foreign
matter adhesion area in the surface of the polishing member; and an
output device for outputting the foreign matter adhesion position
or the foreign matter adhesion area specified by the arithmetic
unit.
[0057] According to this apparatus, standard patterns can be
produced by using the read geometric parameters of a polishing
apparatus and the read polishing conditions for polishing a
polishing object. There is, therefore, no need to previously
prepare standard patterns. Further, when scratches are formed in a
polished surface of a polishing object, a foreign matter adhesion
position or a foreign matter adhesion area in a surface of a
polishing member can be specified by image analysis with the
arithmetic unit using standard patterns, produced in the
above-described manner, and a shot image of the polished surface of
the polishing object, read by the image reading device.
Accordingly, an operation for removal of foreign matter from the
surface of the polishing member can be effectively performed. The
reading device for reading geometric parameters of a polishing
apparatus and the reading device for reading a shot image of a
polished surface of a polishing object may, of course, comprise a
common device having the both functions.
[0058] The present invention also provides a program for causing a
computer to control an apparatus, for cleaning off foreign matter
adhering to a surface of a polishing member, to perform operations
of: an adhesion region specifying step of specifying a foreign
matter adhesion position or a foreign matter adhesion area in a
surface of the polishing member; an intensive cleaning conditions
reading step of reading cleaning conditions for use in carrying out
intensive cleaning on the surface of the polishing member; and an
intensive cleaning step of intensively cleaning the specified
foreign matter adhesion position or foreign matter adhesion area in
the surface of the polishing member under the read intensive
cleaning conditions.
[0059] This program can cause a computer, for cleaning off foreign
matter from a surface of a polishing member, to perform an adhesion
region specifying step, an intensive cleaning conditions reading
step, and an intensive cleaning step.
[0060] The present invention also provides another program for
causing a computer to control an apparatus, for preventing adhesion
of foreign matter to a surface of a polishing member, to perform
operations of: an intensive cleaning region reading step of reading
information on an intensive cleaning position or an intensive
cleaning area in a surface of the polishing member from a storage
medium; an intensive cleaning conditions reading step of reading
cleaning conditions for use in carrying out intensive cleaning on a
surface of the polishing member; and an intensive cleaning step of
cleaning the read intensive cleaning position or intensive cleaning
area in the surface of the polishing member under the read
intensive cleaning conditions.
[0061] This program can cause a computer, for preventing adhesion
of foreign matter to a surface of a polishing member, to perform an
intensive cleaning region reading step, an intensive cleaning
conditions reading step, and an intensive cleaning step.
[0062] The present invention also provides still another program
for causing a computer to control an apparatus, for preventing
adhesion of foreign matter to a surface of a polishing member or
for cleaning off foreign matter adhering to the surface of the
polishing member, to perform operations of: an intensive cleaning
region reading step of reading information on an intensive cleaning
position or an intensive cleaning area in the surface of the
polishing member from a storage medium; an adhesion region
specifying step of specifying a foreign matter adhesion position or
a foreign matter adhesion area in the surface of the polishing
member; an intensive cleaning conditions reading step of reading
cleaning conditions for use in carrying out intensive cleaning on
the surface of the polishing member; and an intensive cleaning step
of cleaning at least one of the read intensive cleaning position or
intensive cleaning area in the surface of the polishing member and
the specified foreign matter adhesion position or foreign matter
adhesion area in the surface of the polishing member under the read
intensive cleaning conditions.
[0063] This program can cause a computer, for preventing adhesion
of foreign matter to a surface of a polishing member or for
cleaning off foreign matter adhering to the surface of the
polishing member, to perform an intensive cleaning region reading
step, an adhesion region specifying step, an intensive cleaning
conditions reading step, and an intensive cleaning step.
[0064] The present invention also provides still another program
for causing a computer to control an apparatus, for preventing
adhesion of foreign matter to a surface of a polishing member or
for cleaning off foreign matter adhering to the surface of the
polishing member, to perform operations of: an adhesion region
specifying step of specifying a foreign matter adhesion position or
a foreign matter adhesion area in the surface of the polishing
member; an adhesion region storing step of storing foreign matter
adhesion positions or foreign matter adhesion areas in the surface
of the polishing member; an intensive cleaning region calculation
step of calculating an intensive cleaning position or an intensive
cleaning area in the surface of the polishing member from the
stored foreign matter adhesion positions or foreign matter adhesion
areas; an intensive cleaning conditions reading step of reading
cleaning conditions for use in carrying out intensive cleaning on
the surface of the polishing member; and an intensive cleaning step
of cleaning at least one of the calculated intensive cleaning
position or intensive cleaning area in the surface of the polishing
member and the specified foreign matter adhesion position or
foreign matter adhesion area in the surface of the polishing member
under the read intensive cleaning conditions.
[0065] This program can cause a computer, for preventing adhesion
of foreign matter to a surface of a polishing member or for
cleaning off foreign matter adhering to the surface of the
polishing member, to perform an adhesion region specifying step, an
adhesion region storing step, an intensive cleaning region
calculation step, an intensive cleaning conditions reading step,
and an intensive cleaning step.
[0066] The foreign matter adhesion position or the foreign matter
adhesion area is specified in the adhesion region specifying step
by, for example, detecting adhesion of foreign matter to the
surface of the polishing member by a detection section.
[0067] This makes it possible to cause a computer to perform the
adhesion region specifying step for detecting foreign matter on the
surface of the polishing member with detecting section.
[0068] The adhesion region specifying step may include a step of
performing image analysis of the surface of the polishing member to
detect adhesion of the foreign matter to the surface.
[0069] This makes it possible to cause the computer to perform the
adhesion region specifying step including a step of performing
image analysis of the surface of the polishing member to detect
adhesion of the foreign matter to the surface.
[0070] Alternatively, the foreign matter adhesion position or the
foreign matter adhesion area may be specified in the adhesion
region specifying step by evaluating a polished surface of a
polishing object.
[0071] This makes it possible to cause the computer to perform the
adhesion region specifying step for specifying the foreign matter
adhesion position or the foreign matter adhesion area by evaluating
a polished surface of a polishing object.
[0072] The adhesion region specifying step may include a step of
performing image analysis of the polished surface of the polishing
object after polishing to evaluate the polished surface.
[0073] This makes it possible to cause the computer to perform the
adhesion region specifying step including a step of performing
image analysis of the polished surface of the polishing object
after polishing to evaluate the polished surface.
[0074] The present invention also provides still another program
for causing a computer to control an apparatus, for storing foreign
matter adhesion positions or foreign matter adhesion areas in a
surface of a polishing member, to perform operations of: a step of
evaluating the surface of the polishing member to specify a foreign
matter adhesion position or a foreign matter adhesion area in the
surface of the polishing member as a position or an area to be
intensively cleaned; and a step of storing the specified intensive
cleaning position or intensive cleaning area.
[0075] This program can cause a computer to perform a step for
storing a foreign matter adhesion position or a foreign matter
adhesion area.
[0076] The present invention also provides still another program
for causing a computer to control an apparatus, for specifying a
foreign matter adhesion position or a foreign matter adhesion area
in a surface of a polishing member, to perform operations of:
polishing step of polishing a polishing object by applying pressure
between the polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other; and an adhesion region specifying step of evaluating a
polished surface of the polishing object to specify a foreign
matter adhesion position or a foreign matter adhesion area in the
surface of the polishing member, which position or area is to be
intensively cleaned.
[0077] This program can cause a computer to perform a step for
specifying a foreign matter adhesion position or a foreign matter
adhesion area in the surface of the polishing member.
[0078] The program may be for also causing the computer to perform
a step of storing data on the specified foreign matter adhesion
position or foreign matter adhesion area in the surface of the
polishing member.
[0079] This makes it possible to cause the computer to perform a
step of storing data on the specified foreign matter adhesion
position or foreign matter adhesion area.
[0080] The adhesion region specifying step may include a step of
performing image analysis of the polished surface of the polishing
object to evaluate the polished surface.
[0081] This makes it possible to cause the computer to perform the
adhesion region specifying step including a step of performing
image analysis of the polished surface of the polishing object to
evaluate the polished surface.
[0082] The present invention also provides still another program
for causing a computer to control an apparatus, for specifying a
foreign matter adhesion position or a foreign matter adhesion area
in a surface of a polishing member, to perform an operation of: an
adhesion region specifying step for specifying a foreign matter
adhesion position or a foreign matter adhesion area in the surface
of the polishing member by image analysis of a shot image of a
polished surface of a polishing object.
[0083] This makes it possible to cause a computer to perform an
adhesion region specifying step for specifying a foreign matter
adhesion position or a foreign matter adhesion area in the surface
of the polishing member.
[0084] The present invention also provides a computer readable
storage medium storing the above-described program.
[0085] The present invention also provides still another polishing
apparatus for polishing a polishing object by applying pressure
between a polishing member and the polishing object while moving
the polishing member and the polishing object relative to each
other, comprising a computer capable of reading the program from
the above-described storage medium and executing the program.
[0086] By thus storing the program in a computer readable storage
medium and reading the program from the storage medium for causing
a computer to control an apparatus, a polishing apparatus, which
can prevent the lowering of the yield due to scratches, can be
provided.
[0087] The present invention also provides still another apparatus
for specifying a foreign matter adhesion position or a foreign
matter adhesion area in a surface of a polishing member, comprising
a computer capable of reading the program from the above-described
storage medium and executing the program.
[0088] By thus storing the program in a computer readable storage
medium and reading the program from the storage medium for causing
a computer to control an apparatus, an adhesion region specifying
apparatus, which specifies a foreign matter adhesion position or a
foreign matter adhesion area in a surface of a polishing member,
which would cause scratches, can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0089] FIGS. 1A and 1B are diagrams illustrating a foreign matter
adhesion position or a foreign matter adhesion area in a surface of
a polishing member;
[0090] FIGS. 2A through 2C are diagrams showing an adhesion region
specifying section which specifies a foreign matter adhesion
position or a foreign matter adhesion area in a surface of a
polishing member by using a pressure sensor;
[0091] FIGS. 3A through 3C are diagrams showing an adhesion region
specifying section which specifies a foreign matter adhesion
position or a foreign matter adhesion area in a surface of a
polishing member by using a displacement sensor;
[0092] FIG. 4 is a diagram showing an adhesion region specifying
section which specifies a foreign matter adhesion position or a
foreign matter adhesion area in a surface of a polishing member by
a non-contact method;
[0093] FIG. 5 is a diagram showing an adhesion region specifying
section which evaluates a polished surface of a polishing object by
a non-contact method to specify a foreign matter adhesion position
or a foreign matter adhesion area in a surface of a polishing
member;
[0094] FIG. 6 is a plan view showing the layout of a chemical
mechanical polishing apparatus according to an embodiment of the
present invention;
[0095] FIG. 7 is a schematic cross-sectional diagram showing a top
ring and part of a polishing table;
[0096] FIGS. 8A through 8E are diagrams showing examples of scratch
patterns for use as standard patterns;
[0097] FIGS. 9A through 9C are diagrams illustrating a method for
calculating the probability of adhesion of foreign matter from
stored data on foreign matter adhesion areas specified by an
adhesion region specifying section;
[0098] FIG. 10 is a control flow diagram of a main routine for
polishing;
[0099] FIG. 11 is a control flow diagram of a routine for
determination of the completion of preparations for polishing;
[0100] FIG. 12 is a control flow diagram of a dressing routine;
[0101] FIG. 13 is a control flow diagram of a polishing pad
cleaning routine;
[0102] FIG. 14 is a control flow diagram of a routine for
monitoring adhesion of foreign matter by evaluation of a polishing
pad;
[0103] FIG. 15 is a control flow diagram for determination of
adhesion of foreign matter by evaluation of a polished surface;
[0104] FIG. 16 is a control flow diagram for the calculation of an
intensive cleaning area;
[0105] FIG. 17 is a systematic diagram of an adhesion region
specifying device; and
[0106] FIG. 18 is a flow diagram of a process for specifying a
foreign matter adhesion area in the adhesion region specifying
apparatus shown in FIG. 17.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0107] Preferred embodiments of the present invention will now be
described with reference to the drawings.
[0108] At the outset, the terms "foreign matter adhesion position"
and "foreign matter adhesion area", in a surface of a polishing
member, such as a polishing pad, to which foreign matter is
adhering, will be described with reference to FIGS. 1A and 1B. In
general, a polishing member, such as a polishing pad, is not in a
fixed or stationary state during polishing, but is making a
rotational movement in the case of a rotary polishing member 200,
as shown in FIG. 1A, or a linear movement in the case of an endless
belt-type polishing member 202, as shown in FIG. 1B.
[0109] The term "foreign matter adhesion position" refers to the
exact position of adherent foreign matter in a surface of a
polishing member. Thus, as shown in FIG. 1A, when a fixed reference
coordinate system (polar coordinate system is illustrated in the
Figure) is taken on the surface of the rotary polishing member 200,
the coordinates (R1, .theta.), at which foreign matter F is
adhering to the surface of the polishing member 200, represent the
foreign matter adhesion position. When a fixed reference coordinate
system is taken on the surface of the endless belt-type polishing
member 202, as shown in FIG. 1B, the coordinates (L1, H), at which
foreign matter F is adhering to the surface of the polishing member
202, represent the foreign matter adhesion position. The reference
coordinate systems rotate or move linearly together with the
surfaces of the polishing members.
[0110] The term "foreign matter adhesion area" refers to that area
in a surface of a polishing member in which, when the polishing
member is in a stationary state, foreign matter may possibly be
adhering to the surface of the polishing member. Thus, in the case
of the rotary polishing member 200, a foreign matter adhesion area
may be represented, for example, by the circle with the radius R1,
the center coinciding with the rotation center of the polishing
member 200 (i.e., circumferential position .theta. not specified),
or by an annular area with an inside diameter of R2 and an outside
diameter of R3 (R2.noteq.R3), as shown in FIG. 1A. In the case of
the endless belt-type polishing member 202, a foreign mater
adhesion area may be represented, for example, by the line with the
distance L1 from the edge of the belt (i.e., position H in the
moving direction of the belt not specified), or by an area with the
distance from the edge of the belt ranging from L2 to L3
(L2.noteq.L3), as shown in FIG. 1B.
[0111] A description will now be given of an adhesion region
specifying section which detects foreign matter on a surface of a
polishing member to specify a foreign matter adhesion position or a
foreign matter adhesion area in the surface of the polishing
member, which position or area is to be subjected to cleaning. An
adhesion region specifying section, comprising a detection section
for detecting foreign matter by a contact method, detects adhesion
of foreign matter to a surface of a polishing member by bringing
the detection section, e.g., comprised of a presser sensor or a
displacement sensor, into contact with the surface of the polishing
member, thereby specifying a foreign matter adhesion position or a
foreign matter adhesion area in the surface of the polishing
member. The displacement sensor may be, for example, a
commercially-available contact-type displacement sensor, or a
displacement sensor comprised of a detection piece to be in contact
with a polishing member, and a reading mechanism for reading a
detected displacement. A commercially-available contact-type or
non-contact-type displacement sensor can be used as the reading
mechanism.
[0112] FIGS. 2A through 2C show an exemplary adhesion region
specifying section 206 which employs, as a detection section, a
plurality of pressure sensors 204 disposed in contact with a
surface of a rotary polishing member 200. As shown in FIG. 2A, the
pressure sensors (detection section) 204, for detecting foreign
matter adhering to the surface of the polishing member 200, are
disposed, with their pressure detection faces in contact with the
surface of the polishing member 200, along a radial direction of
the polishing member 200, the radial center being the rotation
center of the polishing member 200. The polishing member 200
rotates about its rotation center. The pressure sensors 204 are
fixed at certain positions without changing the positions. Thus,
the pressure sensors 204 and the polishing member 200 will move
relative to each other. The pressure detection face of each
pressure sensor 204, which is in contact with the polishing member
200, will move relative to the surface of the polishing member 200
in an annular trajectory with a certain width.
[0113] In order to thoroughly inspect the presence or absence of
foreign matter in that area of the surface of the polishing member
200 to which adhesion of foreign matter must be avoided, the
pressure sensors 204 are preferably disposed so that their adjacent
annular trajectories partly overlap. The pressure sensors 204
should preferably be disposed so that their pressure detection
faces fully cover, by rotation of the polishing member 200, at
least that area of the surface of the polishing member 200 which
may possibly come into contact with a polishing object 210, such as
a semiconductor wafer, held, e.g., by a polishing head 208.
[0114] Since it suffices if the pressure sensors 204 are so
disposed as to meet the above requirements, their arrangement is
not limited to the arrangement along one radial direction shown in
FIG. 2A. For example, it is possible to dispose the pressure
sensors 204 evenly along three radial directions of the polishing
member 200, with adjacent radial directions forming an angle of
120.degree.. Such an arrangement of the pressure sensors 204
enables quick detection of foreign matter (i.e., detectable during
120'-rotation of the polishing member 200). On the other hand, a
relatively large number of pressure sensors are needed. The
intended object may also be achieved if the pressure sensors are
not disposed along a radial direction of the polishing member 200
but disposed at different circumferential positions as viewed from
the rotation center of the polishing member 200.
[0115] As shown in FIG. 2B, a wire 214 is connected to each
pressure sensor 204 so that a pressure read signal can be
transmitted to a data processing device, e.g., comprising a
computer 212. Instead of using a wire, it is also possible to
transmit a pressure signal by using a wireless transmission
device.
[0116] While the adhesion region specifying section 206 has been
described in terms of its application to the rotary polishing
member 200 shown in FIG. 1A, the same holds true for application to
the endless belt-type polishing member 202 shown in FIG. 1B. Thus,
the pressure sensors 204 may be disposed on the surface of the belt
in a line or lines orthogonal to the moving direction of the belt.
Alternatively, the pressure sensors 204 may be disposed randomly
without forming a line orthogonal to the moving direction of the
belt. What is needed is to dispose the pressure sensors so that the
pressure detection faces, or their trajectories fully cover that
area of the surface of the endless belt-type polishing member 202
to which foreign matter may adhere and which should therefore be
detected.
[0117] A description will now be given of a method for detecting
foreign matter F adhering to the surface of the polishing member
200 by the pressure sensors 204. Foreign matter F adhering to the
surface of the polishing member 200 protrudes from the surface, as
shown in FIG. 2B. Accordingly, when the foreign matter F passes
between the surface of the polishing member 200 and one of the
pressure sensors 204, disposed as shown in FIG. 2A, the pressure
read signal of the pressure sensor 204 changes and shows a peak P,
as shown in FIG. 2C. Thus, adhesion of the foreign matter F to the
surface of the polishing member 200 can be detected by monitoring
the pressure read signals of the pressure sensors 204 with, e.g., a
computer for controlling the polishing apparatus.
[0118] The foreign matter adhesion area in the polishing member 200
can be specified from the position of the particular pressure
sensor 204, of the plurality of pressure sensors 204, which has
detected the foreign matter F, or from the surface measuring range
of the particular pressure sensor 204. Further, the foreign matter
adhesion position can be specified by setting a reference
coordinate system on the surface of the polishing member 200, and
synchronizing the foreign matter detection time with the time
history of the rotational or linear movement of the reference
coordinate system, e.g., by the computer 212. A foreign matter
adhesion position or a foreign matter adhesion area can be
specified with high precision by using as the pressure sensor 204 a
pressure distribution measuring device (tactile sensor) having a
high spatial resolution.
[0119] As shown in FIG. 2A, a polishing aid 218 is supplied from a
nozzle 216 to the surface of the polishing member 200 during
polishing of the polishing object 210.
[0120] A description will now be given of an adhesion region
specifying section 226 which employs, as a detection section, a
plurality of displacement sensors 224 each including a detection
piece 220 in contact with the polishing member 200, and a
displacement reading mechanism 222 for reading a displacement of
the detection piece 220, as shown in FIGS. 3A through 3C.
[0121] The displacement sensors (detection section) 224, used in
the adhesion region specifying section 226 shown in FIGS. 3A and
3B, each comprises a detection piece 220, a displacement reading
mechanism 222 so disposed as to read a displacement of the
detection piece 220, and a holder 228 which holds the displacement
reading mechanism 222 in a limited space without changing the
position of the displacement reading mechanism 222. The detection
piece 220 is so adapted that when foreign matter F is present on
the surface of the polishing member 200, protruding from the
surface, the detection piece 220 changes its position upon contact
with the foreign matter F when the polishing member 200 is
rotating. Accordingly, the relative position between the
displacement reading mechanism 222 and the detection piece 220
changes by the presence of the foreign matter F on the surface of
the polishing member 200. The displacement reading mechanism 222
can therefore send a displacement signal with a peak P, as shown in
FIG. 3C.
[0122] A common contact-type or non-contact-type displacement
sensor can be used as the displacement reading mechanism 222. The
presence of foreign matter F on the polishing member 200 is first
caught by a change in the position of the detection piece 220, the
change is then detected by the displacement reading mechanism 222,
using, e.g., a common non-contact-type displacement sensor, which
generates a displacement signal, and the signal is recognized,
e.g., by the computer 212.
[0123] Like the polishing object 210 being polished, the detection
piece 220 is also polished and worn out though only gradually.
Accordingly, a displacement of the detection piece 220, which is
read by the displacement reading mechanism 222, changes with time
even in the absence of foreign matter F. A means is therefore
needed which will compensate for a change in the relative position
between the displacement reading mechanism 222 and the detection
piece 220 due to the wear of the detection piece 220. Such means
include signal filtering, such as high-pass filtering or
differential filtering, of the displacement signal of the
displacement reading mechanism 222, a means for compensating for a
change in the relative position by using a pre-measured wearing
rate of the detection piece 220.
[0124] A material hard to be polished is preferably used for the
detection piece 220. Examples of such materials include ceramics,
such as zirconia, alumina, etc. and engineering plastics, such as
an epoxy (EP) resin, a phenol (PF) resin, a polyphenylene sulfide
(PPS) resin, etc.
[0125] While the displacement sensor 224, including the detection
piece 220 and the displacement reading mechanism 222, has been
described, a common contact-type displacement sensor may also be
used.
[0126] The embodiment shown in FIGS. 3A through 3C is a mere
replacement of the pressure sensors 204 in the embodiment shown in
FIGS. 2A through 2C with the displacement sensors 224. Thus, the
idea of detection of foreign matter F, underlying this embodiment,
is basically the same as that of the preceding embodiment that
employs the pressure sensors 204. FIG. 3A corresponds to FIG. 2A,
illustrating this embodiment in terms of its application to the
rotary polishing member 200. As shown in FIG. 3A, the displacement
sensors 224 for detecting foreign matter F adhering to the surface
of the polishing member 200 are disposed, with the detection pieces
220 in contact with the surface of the polishing member 200, along
a radial direction of the polishing member 200, the radial center
being the rotation center of the polishing member 200. The
polishing member 200 rotates about its rotation center. The
displacement reading mechanism 222 of each displacement sensor 224
is fixed at a certain position, e.g., by the holder 228 so that the
mechanism 222 will not change its position.
[0127] The detection piece 220 of each displacement sensor 224 is
movably held, e.g., by the holder 228. Thus, while the holder 228
and the displacement reading mechanism 222 of the displacement
sensor 224 are fixed at certain positions, only the detection piece
220 is movable. The polishing member 200 moves relative to such
displacement sensors 224. That portion of the detection piece 220
of each displacement 224, which is in contact with the surface of
the polishing member 200, will move relative to the surface of the
polishing member 200 in an annular trajectory with a certain width.
In order to thoroughly inspect the presence or absence of foreign
matter in that area of the surface of the polishing member 200 to
which adhesion of foreign matter must be avoided, the displacement
sensors 224 are preferably disposed so that their adjacent annular
trajectories partly overlap. The displacement sensors 224 should
preferably be disposed so that the detection pieces 220 fully
cover, by rotation of the polishing member 200, at least that area
of the surface of the polishing member 200 which may possibly come
into contact with the polishing object 210 held, e.g., by the
polishing head 208.
[0128] Since it suffices if the displacement sensors 224 are so
disposed as to meet the above requirements, their arrangement is
not limited to the arrangement along one radial direction shown in
FIG. 3A. For example, it is possible to dispose the displacement
sensors 224 evenly along two radial directions of the polishing
member 200, the radial directions forming an angle of 180.degree..
Such an arrangement of the displacement sensors 224 enables quick
detection of foreign matter (i.e., detectable during
180.degree.-rotation of the polishing member 200). On the other
hand, a relatively large number of displacement sensors are needed.
The intended object may also be achieved if the displacement
sensors are not disposed along a radial direction of the polishing
member 200 but disposed at different circumferential positions as
viewed from the rotation center of the polishing member 200.
[0129] As shown in FIG. 3B, a wire 214 is connected to each
displacement sensor 224 so that a displacement signal can be
transmitted to a data processing device, e.g., comprising a
computer 212.
[0130] While the adhesion region specifying section 226 has been
described in terms of its application to the rotary polishing
member 200 shown in FIG. 1A, the same holds true for its
application to the endless belt-type polishing member 202 shown in
FIG. 1B. Thus, what is needed with the endless belt-type polishing
member 202 is to dispose the displacement sensors so that the
trajectories of the detection pieces fully cover that area of the
surface of the endless belt-type polishing member 202 to which
foreign matter may adhere and which should therefore be
detected.
[0131] A description will now be given of a method for detecting
foreign matter F adhering to the surface of the polishing member
200 by the displacement sensors 224. Foreign matter F adhering to
the surface of the polishing member 200 protrudes from the surface,
as shown in FIG. 3B. Accordingly, when the foreign matter F passes
between the surface of the polishing member 200 and one of the
detection pieces 220 of the displacement sensors 224, disposed as
shown in FIG. 3A, the displacement read signal of the displacement
sensor 224 changes and shows a peak P, as shown in FIG. 3C. Thus,
adhesion of the foreign matter F to the surface of the polishing
member 200 can be detected by monitoring the displacement read
signals of the displacement sensors 224 with, e.g., a computer for
controlling the polishing apparatus. The foreign matter adhesion
area in the polishing member 200 can be specified from the position
of the particular displacement sensor 224, of the plurality of
displacement sensors 224, which has detected the foreign matter F,
or from the surface measuring range of the detection piece 220 of
the particular displacement sensor 224. Further, the foreign matter
adhesion position can be specified by setting a reference
coordinate system on the surface of the polishing member 200, and
synchronizing the foreign matter detection time with the time
history of the rotational or linear movement of the reference
coordinate system, e.g., by the computer 212.
[0132] The specification of a foreign matter adhesion position or a
foreign matter adhesion area in a polishing member by the
above-described adhesion region specifying sections, each including
the contact-type foreign matter detection section, can be performed
at any time when the polishing member is moving, such as before,
during or after polishing of a polishing object, or during dressing
of the polishing member. By carrying out the specifying operation
during polishing, foreign matter can be detected immediately after
its adhesion to the polishing member.
[0133] A description will now be given of an adhesion region
specifying section which detects foreign matter on a surface of a
polishing member by a non-contact-type detection section to specify
a foreign matter adhesion position or a foreign matter adhesion
area in the surface of the polishing member, which position or area
is to be subjected to cleaning. Such an adhesion region specifying
section, having a non-contact-type foreign matter detection
section, specifies a foreign matter adhesion position or a foreign
matter adhesion area in a surface of a polishing member by
detecting foreign matter on the surface of the polishing member
without bringing into contact with the polishing member, such as by
shooting the surface of the polishing member and analyzing a shot
image of the surface.
[0134] An adhesion region specifying section, for example,
including a photographic device, as a detection section, for
shooting a surface of a polishing member, and an arithmetic unit
for analyzing a shot image, will now be described first of its
construction and then of its image analysis.
[0135] A photographic device (detection section) 230 may be set at
a position, above a polishing member 200, at which shooting of the
surface of the polishing member 200 is possible, as shown in FIG.
4. The photographic device 230 may be either for a moving image or
for a still image, and may be either an analog photographic device
or a digital photographic device. A shot image is analyzed by an
arithmetic unit 232, as will be described below, and, from the
viewpoint of easy image analysis, the photographic device 230
preferably is a digital, still-image photographic device, such as a
CCD camera.
[0136] An adhesion region specifying section 234 includes the
arithmetic unit 232 for making an image analysis of a shot image.
An image shot by the photographic device 230 is transmitted, e.g.,
in the form of image data, through a wire 233 to the arithmetic
unit 232 where the shot image is analyzed. A common computer,
capable of executing image analysis by an image analysis software
or an auxiliary image analysis circuit, a computer exclusively for
image analysis, a digital image analysis circuit, an analog image
analysis circuit, etc. can be used as the arithmetic unit 232. The
arithmetic unit 232 may also have a control function for the
photographic device 230.
[0137] In this embodiment, an image refers to an analog image,
digital image data, or an analog electrical signal converted from
an analog image or digital image data.
[0138] Image analysis by the adhesion region specifying section 234
will now be described. The polishing surface of the polishing
member 200 is divided into an appropriate number of zones 236, and
a shooting area 238 that includes a zone 236, preferably also
includes an area surrounding the zone, is shot by the photographic
device 230. All the zones 236 are thus shot sequentially. Image
transformation of a shot image for image corrections and feature
extraction on the transformed image are performed by the arithmetic
unit 232. The image transformation may include spatial filtering
for denoising, distortion correction, deblurring, sharpening, image
enhancement, etc., spectral transformation, Walsh transform,
wavelet transform, normalization, etc. The feature extraction may
include edge extraction, line extraction, contour extraction, color
extraction, density extraction, texture extraction, etc.
[0139] Thereafter, image recognition is performed by the arithmetic
unit 232 to determine whether foreign matter is adhering to the
surface of the polishing member 200 or not. The image recognition
may include pattern recognition, such as the nearest neighbor
method, Bayes decision rule, dynamic programming matching (DP
matching), Hidden Markov Model, etc. In this embodiment, image
analysis implies execution of at least one of image transformation,
feature extraction and image recognition. Determination can be made
by image analysis as to whether foreign matter is adhering to the
surface of the polishing member 200 or not.
[0140] Though, in this embodiment, the surface of the polishing
member 200 is divided into the zones 236 and the corresponding
shooting areas 238 are shot sequential, it is also possible to
shoot the entire polishing member 200 at once. The number of the
zones 236 is not particularly limited. A position or area, in the
surface of the polishing member 200, in which the presence of
foreign matter F is determined by image recognition, can be
specified as the foreign matter adhesion position or the foreign
matter adhesion area. As with the above-described contact-type
detection sections, it is also possible to set a reference
coordinate system on the surface of the polishing member 200, and
synchronize the time of detection of foreign matter with the time
history of rotational or linear movement of the reference
coordinate system by, e.g., a computer for controlling the
polishing apparatus, thereby specifying the foreign matter adhesion
position or the foreign matter adhesion area in the surface of the
polishing member 200.
[0141] A CCD camera may be conveniently used as the photographic
device 230. The use of a CCD camera enables the use of a digital
arithmetic unit 232 for image analysis. It is, of course, possible
to use an analog camera as the photographic device 230 and perform
image analysis with a digital arithmetic unit 232 through A/D
conversion of an image signal. This holds true for other
photographic devices.
[0142] The arithmetic unit 232 may be either an arithmetic unit for
exclusive use in the adhesion region specifying section 234 or a
computer also used to control the polishing apparatus.
[0143] In a case where polishing is carried out using an opaque
polishing aid, detection of foreign matter on the surface of the
polishing member 200 by the adhesion region specifying section 234,
which employs the above-described non-contact detection method, is
preferably carried out when there is little polishing aid on the
surface of the polishing member 200, such as during or after
dressing of the polishing member 200. FIG. 4 illustrates detection
of foreign matter F on the surface of the polishing member 200 when
the polishing member 200 is being dressed with a dresser 244 while
supplying pure water 242 from a nozzle 240 to the surface of the
polishing member 200. During supply of an opaque polishing aid or
when a large amount of the polishing aid remains on the surface of
the polishing member 200, the surface is covered with the opaque
polishing aid, making detection of foreign matter difficult.
[0144] Detection of foreign matter on the surface of the polishing
member 200 by the adhesion region specifying section 234, which
employs the above-described non-contact detection method, can be
carried out irrespective of whether the polishing member 200 is
moving or not. When the polishing member 200 is moving, the zones
236 are also moving. Shooting of the zones 236 is therefore carried
out with timing synchronous with the movement of the polishing
member 200. When the polishing member 200 is not moving, the entire
zones 236 of the polishing surface are shot, e.g., by moving the
photographic device 230. The entire polishing member 200 may be
shot at once, as described above.
[0145] While the adhesion region specifying sections having a
detection section have been described, an adhesion detection
specifying section is not necessary provided with a detection
section. For example, it is possible to carry out a simulation by
using a computer to obtain information on a position or area of
high probability of adhesion of foreign matter, and input the
information into an adhesion region specifying section not having a
detection section. It is also possible to use an adhesion region
specifying section which itself has such a simulation function
Furthermore, it is possible to use an adhesion region specifying
section which stores information on foreign matter adhesion
positions or foreign matter adhesion areas specified by the
adhesion region specifying section, and specifies a foreign matter
adhesion position or a foreign matter adhesion area based on the
stored information. It is not necessary for such adhesion region
specifying sections to carry out detection of foreign matter on a
polishing member in use.
[0146] A description will now be given of an adhesion region
specifying section which evaluates by image analysis of a surface
(polished surface) of a polishing object after polishing. Such an
adhesion region specifying section carries out shooting of a
surface of a polishing object after polishing and image analysis of
a shot image to detect a scratch or scratches in the surface,
thereby indirectly specifying a foreign matter adhesion position or
a foreign matter adhesion area in a surface of a polishing member.
An adhesion region specifying section which uses a photographic
device, as a detection section, for shooting a surface (polished
surface) of a polishing object after polishing, and includes an
arithmetic unit (evaluation device or image analyzer) for analyzing
a shot image, for example, will now be described first of its
construction and then of its image analysis.
[0147] A photographic device (detection section) 250 may be set at
a position at which shooting of a surface (polished surface) 210a
of a polishing object 210, such as a semiconductor wafer, held on a
holder 246 is possible, as shown in FIG. 5. The photographic device
250 may be either for a moving image or for a still image, and may
be either an analog photographic device or a digital photographic
device. A shot image is analyzed by an arithmetic unit (evaluation
device or image analyzer) 252, as will be described below, and,
from the viewpoint of easy image analysis, the photographic device
250 preferably is a digital, still-image photographic device, such
as a CCD camera.
[0148] The adhesion region specifying section 254 includes the
arithmetic unit 252 for making an image analysis of a shot image.
An image shot by the photographic device 250 is transmitted, e.g.,
in the form of image data, through a wire 253 to the arithmetic
unit 252 where the shot image is analyzed. A common computer,
capable of executing image analysis by an image analysis software
or an auxiliary image analysis circuit, a computer exclusively for
image analysis, a digital image analysis circuit, an analog image
analysis circuit, etc. can be used as the arithmetic unit 252. The
arithmetic unit 252 may also have a control function for the
photographic device 250.
[0149] In this embodiment, an image refers to an analog image,
digital image data, or an analog electrical signal converted from
an analog image or digital image data.
[0150] Image analysis by the adhesion region specifying section 254
will now be described. The surface (polished surface) 210a of the
polishing object 210 after polishing is divided into an appropriate
number of zones 256, and a shooting area 258 that includes a zone
256, preferably also includes an area surrounding the zone 256, is
shot by the photographic device 250. All the zones 256 are thus
shot sequentially. Image transformation of a shot image for image
corrections and feature extraction on the transformed image are
performed by the arithmetic unit 252. The image transformation may
include spatial filtering for denoising, distortion correction,
deblurring, sharpening, image enhancement, etc., spectral
transformation, Walsh transform, wavelet transform, normalization,
etc. The feature extraction may include edge extraction, line
extraction, contour extraction, color extraction, density
extraction, texture extraction, etc.
[0151] Thereafter, image recognition is performed by the arithmetic
unit (evaluation device or image analyzer) 252 to detect (extract)
a scratch or scratches 210b formed in the surface 210a of the
polishing object 210 after polishing. The presence of a scratch or
scratches 210b in the surface 210a of the polishing object 210
after polishing indicates adhesion of foreign matter to a surface
of a polishing member. The image recognition may include pattern
recognition, such as the nearest neighbor method, Bayes decision
rule, dynamic programming matching (DP matching), Hidden Markov
Model, etc. In this embodiment, image analysis implies execution of
at least one of image transformation, feature extraction and image
recognition.
[0152] The use of the adhesion region specifying section 254 can
indirectly detect adhesion of foreign matter to a surface of a
polishing member. By determining a width, length, depth, etc. of a
scratch with the arithmetic unit 252, the scratch can be checked to
see if it is a fatal defect or not. When the scratch is a fetal
defect, an appropriate action, such as immediately stopping
polishing and cleaning the surface of the polishing member, can be
taken. Polishing can be continued when the scratch is not a fetal
defect. The lowering of the yield can therefore be prevented while
minimizing the lowering of the throughput of polishing.
[0153] The arithmetic unit 252 may be either an arithmetic unit for
exclusive use with the adhesion region specifying section 254 or a
computer also used to control the polishing apparatus.
[0154] In the case where a polishing object is a semiconductor
wafer, various wafer defect inspection apparatuses and foreign
matter inspection apparatuses, which are commercially available
from manufactures of semiconductor device inspection apparatuses,
can be used for detection of scratches or for determination as to
whether a scratch is a fetal defect or not. Such a
commercially-available defect inspection apparatus, when used in
combination with the adhesion region specifying section 254 to
detect scratches 210b in the surface (polished surface) 210a of the
polishing object 210, will contribute to maintaining the throughput
at a high level.
[0155] A description will now be given of a method for specifying a
foreign matter adhesion position or a foreign matter adhesion area
in a polishing surface of a polishing member based on evaluation,
by image analysis, of the surface (polished surface) 210a of the
polishing object 210 after polishing. The foreign matter specifying
method comprises shooting the surface (polished surface) 210a of
the polishing object 210 after polishing, performing image analysis
of a shot image, and specifying, from a scratch or scratches 210b
in the surface 210a, a foreign matter adhesion position or a
foreign matter adhesion area in the surface of the polishing
member.
[0156] The detection of a scratch or scratches in the surface
(polished surface) 210a of the polishing object 210 is carried out,
for example, with the above-described adhesion region specifying
section 254. The adhesion region specifying section 254 includes
the arithmetic unit 252 for performing image analysis of a scratch
or scratches detected by the photographic device (detection
section) 250.
[0157] A method is known in which a foreign matter adhesion
position or a foreign matter adhesion area in a polishing member is
specified from a formulated scratch track, using the center of the
circle of curvature and the radius of curvature at a point on a
scratch and geometric parameters of the polishing apparatus, as
described in Japanese Patent Laid-Open Publication No. 2004-259871.
The geometric parameters of polishing apparatus are parameters
which are determined by positional relationships between elements
of the apparatus, such as the distance between the rotation center
of a polishing member and the rotation center of a polishing
object. An arithmetic unit, provided in an adhesion region
specifying section, calculates by image analysis the center of the
circle of curvature and the radius of curvature at a point on a
scratch, and calculates and specifies a foreign matter adhesion
position or a foreign matter adhesion area from the formulated
scratch track.
[0158] This method can determine a foreign matter adhesion position
or a foreign matter adhesion area in a polishing member with high
precision. However, in some cases, for example, in the case where a
polishing object swings on a polishing member, complicate
calculations are required to formulate a scratch track and specify
a foreign matter adhesion position or a foreign matter adhesion
area from the formulated scratch track.
[0159] On the other hand, according to the below-described foreign
matter region specifying method using the adhesion region
specifying section 254 of this embodiment, a foreign matter
adhesion position or a foreign matter adhesion area in a surface of
a polishing member can be easily specified with high precision even
when using a complicated polishing recipe. The method is therefore
very useful.
[0160] First, patterns of scratches, as will be formed in a surface
(polished surface) of a polishing object after polishing with a
polishing member to which foreign matter is adhering, are
calculated for a number of foreign matter adhesion positions or
foreign matter adhesion areas by an arithmetic unit, and the
calculated scratch patterns are stored as standard patterns in a
storage device capable storing a program and/or data. Next, a
scratch pattern (detection pattern) in the surface (polished
surface) of the polishing object after polishing, actually detected
by the adhesion region specifying section 254, is compared with the
standard patterns by the arithmetic unit 252 and, from the degree
of similarity, a foreign matter adhesion position or a foreign
matter adhesion area in the polishing member is specified. The
comparison by the arithmetic unit 252 includes image
recognition.
[0161] A standard pattern may be produced experimentally or by a
simulation. A standard pattern can be produced experimentally, for
example, in the following manner: A polishing object is actually
polished with a polishing member to which foreign matter or an
equivalent of foreign matter is intentionally adhered. A scratch or
scratches produced by polishing are detected by image analysis by
the adhesion region specifying section 254. From the detected
scratches, a desired pattern for use as a standard pattern is
produced as computer-readable image data. In the case of employing
image data as a standard pattern, the produced computer-readable
data is converted into image data and the image data is used as a
standard pattern.
[0162] A standard pattern can be produced by a simulation, for
example, in the following manner: A track of foreign matter,
adhering to a surface of a polishing member, on a surface (to be
polished) of a polishing object is calculated using geometric
parameters of a polishing apparatus, polishing conditions and a
foreign matter adhesion position or a foreign matter adhesion area.
From the track thus calculated, a desired pattern is produced as
computer-readable data. In the case of employing image data as a
standard pattern, the produced computer-readable data is converted
into image data and the image data is used as a standard
pattern.
[0163] A foreign matter adhesion position or a foreign matter
adhesion area in a surface of a polishing member can thus be
specified by using image data on a scratch, detected by the
photographic device 250, as a detection pattern, and comparing the
detection pattern and standard patterns by image recognition using
the arithmetic unit 252.
[0164] The geometric parameters of a polishing apparatus refer to
parameters as determined by positional relationships between
elements of the apparatus, such as the distance between the
rotation center of a polishing member and the rotation center of a
polishing object, and the polishing conditions refer to the
rotational speed (moving speed) of a polishing member, the
rotational speed of a polishing object, the swinging speed of the
polishing object, the swinging range of the polishing object, etc.
Polishing conditions are usually inputted as a polishing recipe
into a polishing apparatus prior to polishing, and thus are known.
Standard patterns, corresponding to foreign matter adhesion
positions, can be produced easily from such a known polishing
recipe even when the polishing conditions are complicated. It is
therefore possible to carry out a simulation using an arithmetic
device or a computer, provided in a polishing apparatus, after
inputting a polishing recipe into the polishing apparatus, to
thereby produce standard patterns.
[0165] Thus, even when a complicated polishing recipe is set, a
foreign matter adhesion position or a foreign matter adhesion area
in a surface of a polishing member can be specified with high
precision. The present method specifies a foreign matter adhesion
position or a foreign matter adhesion area in a surface of a
polishing member by comparison of a detection pattern with standard
patterns. Therefore, the precision can be enhanced by increasing
the number of standard patterns according to necessity. The image
recognition includes pattern recognition, such as the nearest
neighbor method, Bayes decision rule, dynamic programming matching
(DP matching), Hidden Markov Model, etc.
[0166] While the use of image data as a standard pattern has been
described, it is also possible to use as a standard pattern various
data obtainable from scratches, such as a radial density
distribution and a circumferential density distribution of
scratches, the presence or absence of a scratch at a specified
position in a polished surface. In the case of using such standard
patterns, a foreign matter adhesion position or a foreign matter
adhesion area can be specified without carrying out image
recognition.
[0167] For example, in the case of a circular polishing object, a
foreign matter adhesion position or a foreign matter adhesion area
in a polishing member can be specified by using, as a standard
pattern, a radial or circumferential density distribution of
scratches in the polished surface, as follows: From scratches
detected by the photographic device 250, a radial or
circumferential density distribution of the scratches in the
polished surface is first calculated as a detection pattern using
the arithmetic device 252. The arithmetic unit 252 then compares
the detection pattern with the characteristics of distributions in
standard patterns which have previously been calculated and stored
as data, such as the periodicity of distribution of scratches, the
peak position (position at which scratches are concentrated) of
scratches, the peak height (concentration or density of scratches),
etc., thereby specifying an adhesion position or an adhesion area
in the polishing member.
[0168] If the detection pattern does not fully coincide with any of
the standard patterns in terms of distribution characteristics, the
arithmetic unit 252 may then pick out the most similar standard
pattern and specify a position or an area in the polishing member,
corresponding to the most similar standard pattern, as a foreign
matter adhesion position or a foreign matter adhesion area in the
surface of the polishing member. Alternatively, the arithmetic unit
252 may pick out some similar standard patterns, and specify a
foreign matter adhesion position or a foreign matter adhesion area
in the surface of the polishing member by determining the average
or the maximal value in a distribution function of positions or
areas, corresponding to the similar standard patterns. Thus, more
than one foreign matter adhesion position or foreign matter
adhesion area can be specified. This holds true for any other
specifying method.
[0169] The arithmetic unit 252 may be either an arithmetic unit for
exclusive use with the adhesion region specifying section 254 or a
computer also used to control the polishing apparatus.
[0170] FIG. 6 is a plan view showing the layout of a chemical
mechanical polishing apparatus, for mainly polishing a
semiconductor wafer, according to an embodiment of the present
invention. As shown in FIG. 6, the chemical mechanical polishing
apparatus comprises four load/unload stages 22 each for loading a
wafer cassette 21 which accommodates a number of semiconductor
wafers (polishing objects). The load/unload stages 22 may have a
lifting and lowering mechanism. A transport robot 24, having two
hands, is provided on rails 23 so that the transport robot 24 can
access the respective wafer cassettes 21 on the respective
load/unload stages 22.
[0171] Located at a position accessible by the transport robot 24,
there is provided an adhesion region specifying section 120 shown
in FIG. 5, which detects foreign matter adhering to a polishing pad
(polishing member) and specifies the foreign matter adhesion area
in the polishing pad. According to this embodiment, the adhesion
region specifying section 120 is comprised of the adhesion region
specifying section 254 including the photographic device 250 and
the arithmetic unit (evaluation device or image analyzer) 252, as
shown in FIG. 5, and performs detection of foreign matter on the
polishing pad and specification of the foreign matter adhesion area
by evaluating a surface (polished surface) of a semiconductor wafer
after polishing. The adhesion region specifying section 120 is
preferably designed to be capable of evaluating a plurality of
semiconductor wafers in parallel. This makes it possible to carry
out polishing without lowering the processing ability (throughput)
of the polishing apparatus.
[0172] The transport robot 24 has upper and lower hands. The lower
hand of the transport robot 24 is used only for receiving a
semiconductor wafer from the wafer cassette 21. The upper hand of
the transport robot 24 is used for transporting a semiconductor
wafer in or from the adhesion region specifying section 120 and
returning a semiconductor wafer to the wafer cassette 21. Since a
clean semiconductor wafer, which has been cleaned, is held by the
upper hand, the clean semiconductor wafer is not further
contaminated. The lower hand is a vacuum attracting-type hand for
holding a semiconductor wafer under vacuum, and the upper hand is a
recess support-type hand for supporting a peripheral edge of a
semiconductor wafer. The vacuum attracting-type hand can hold and
transport a semiconductor wafer even if the semiconductor wafer is
not located in a normal position. The recess support-type hand can
transport a semiconductor wafer while keeping a lower surface of
the semiconductor wafer clean because dust is not collected.
[0173] Two cleaning devices 25, 26 are disposed at an opposite side
of the wafer cassettes 21 with respect to the rails 23 of the
transport robot 24. The cleaning devices 25, 26 are disposed at
positions accessible by the hands of the transport robot 24.
Between the two cleaning devices 25, 26, a wafer station 70 having
four semiconductor wafer supports 27, 28, 29 and 30 is disposed at
a position accessible by the transport robot 24. Each of the
cleaning devices 25, 26 has a spin-dry mechanism for drying a
semiconductor wafer by spinning it at a high speed, and hence
two-stage cleaning and three-stage cleaning of a semiconductor
wafer can be performed without replacing any cleaning module.
[0174] An area B, in which the cleaning devices 25, 26 and the
supports 27, 28, 29 and 30 are disposed, and an area A, in which
the wafer cassettes 21, the adhesion region specifying section 120
and the transport robot 24 are disposed, are partitioned by a
partition 84 so that the cleanliness of the area A and the area B
can be separated. The partition 84 has an opening for allowing
semiconductor wafers to pass therethrough, and a shutter 31 is
provided at the opening of the partition 84. A transport robot 80,
having two hands, is disposed at a position where the transport
robot 80 can access the cleaning device 25 and the three supports
27, 29 and 30, and a transport robot 81, having two hands, is
disposed at a position where the transport robot 81 can access the
cleaning device 26 and the three supports 28, 29 and 30.
[0175] The support 27 is used to transfer a semiconductor wafer
between the transport robot 24 and the transport robot 80, and has
a sensor 91 for detecting existence of a semiconductor wafer. The
support 28 is used to transfer a semiconductor wafer between the
transport robot 24 and the transport robot 81, and has a sensor 92
for detecting existence of a semiconductor wafer. The support 29 is
used to transport a semiconductor wafer from the transport robot 81
to the transport robot 80, and has a sensor 93 for detecting
existence of a semiconductor wafer and a rinsing nozzle 95 for
preventing a semiconductor wafer from being dried or rinsing a
semiconductor wafer.
[0176] The support 30 is used to transport a semiconductor wafer
from the transport robot 80 to the transport robot 81, and has a
sensor 94 for detecting existence of a semiconductor wafer and a
rinsing nozzle 96 for preventing a semiconductor wafer from being
dried or rinsing a semiconductor wafer. The supports 29, 30 are
disposed in a common water-scatter-prevention cover which has an
opening defined therein for transporting wafers therethrough. At
the opening, there is provided a shutter 97. The support 29 is
disposed above the support 30. The upper support 29 serves to
support a semiconductor wafer which has been cleaned, and the lower
support 30 serves to support a semiconductor wafer to be cleaned.
With this arrangement, the semiconductor wafer is prevented from
being contaminated by rinsing liquid which would otherwise fall
thereon. The sensors 91, 92, 93 and 94, the rinsing nozzles 95, 96,
and the shutter 97 are schematically shown in FIG. 6, and their
positions and shapes are not exactly illustrated.
[0177] The respective upper hands of the transport robots 80, 81
are used for transporting a semiconductor wafer, that has been
cleaned, to the cleaning devices 25, 26 or the supports of the
wafer station 70. On the other hand, the respective lower hands of
the transport robots 80, 81 are used for transporting a
semiconductor wafer, that has not cleaned or a semiconductor wafer
to be polished, to a reversing device. Since the lower hands are
used to transport a semiconductor wafer to or from the reversing
device, the upper hands are not contaminated by drops of rinsing
liquid which fall from an upper wall of the reversing device. A
cleaning device 82 is disposed at a position adjacent to the
cleaning device 25 and accessible by the hands of the transport
robot 80, and another cleaning device 83 is disposed at a position
adjacent to the cleaning device 26 and accessible by the hands of
the transport robot 81. All of the cleaning devices 25, 26, 82 and
83, the supports 27, 28, 29 and 30 of the wafer station 70, and the
transport robots 80, 81 are placed in area B. Pressure in area B is
adjusted so as to be lower than pressure in area A. Each of the
cleaning devices 82, 83 is capable of cleaning both surfaces of a
semiconductor wafer.
[0178] The chemical mechanical polishing apparatus has a housing 66
for enclosing various components therein. The interior of the
housing 66 is partitioned into a plurality of compartments or
chambers (including the areas A and B) by partitions 84, 85, 86, 87
and 67. A polishing chamber is separated from an area A by the
partition 87, and the polishing chamber is divided into an area C
as a first polishing section and an area D as a second polishing
section. In each of the two areas C, D, there are provided two
polishing tables, and a top ring for holding a semiconductor wafer
and pressing the semiconductor wafer against the polishing tables
for polishing. That is, polishing tables 54, 56 are provided in the
area C, and polishing tables 55, 57 are provided in the area D.
Further, a top ring 52 is provided in the area C, and a top ring 53
is provided in the area D.
[0179] The polishing tables 54, 55, 56, 57 are each provided at the
top with a polishing pad 10 (see FIG. 7) as a polishing member. The
polishing tables may have different types of polishing pads
according to different polishing objectives. In the area C are
disposed an abrasive liquid nozzle 60 for supplying a polishing
abrasive liquid to the polishing table 54, and a dresser 58 for
dressing the polishing table 54. In the area C are also disposed an
adhesion region specifying section 110 for detecting foreign matter
adhering to the polishing table 54 and specifying the foreign
matter adhesion area, and a cleaning section 112 for cleaning the
polishing table 54. In the area D are disposed an abrasive liquid
nozzle 61 for supplying a polishing abrasive liquid to the
polishing table 55, and a dresser 59 for dressing the polishing
table 55. In the area D are also disposed an adhesion region
specifying section 111 for detecting foreign matter adhering to the
polishing table 55 and specifying the foreign matter adhesion area,
and a cleaning section 113 for cleaning the polishing table 55.
There are also disposed a dresser 68 for dressing the polishing
table 56 in the area C and a dresser 69 for dressing the polishing
table 57 in the area D.
[0180] The adhesion region specifying sections 110, 111, according
to this embodiment, are each comprised of the adhesion region
specifying section 226 having the displacement sensors 224, shown
in FIGS. 3A and 3B. The adhesion region specifying sections 110,
111 may each be comprised of the adhesion region specifying section
206 having the pressure sensors 204, shown in FIGS. 2A and 2B, or
of the adhesion region specifying section 234 having the
photographic device 230 and the arithmetic unit 232, shown in FIG.
4.
[0181] The adhesion region specifying sections 110, 111 can
therefore detect adhesion of foreign matter to a polishing pad and
specify a foreign matter adhesion area in the polishing pad even
during polishing. The cleaning sections 112, 113 carry out cleaning
of the polishing pad by rubbing the polishing pad with a rotating
brush. The cleaning sections 112, 113 have a mechanism for moving
the brush to an arbitrary radial position on the polishing pad.
Thus, the brush of the cleaning section 112 or 113 can be fixed at
an arbitrary position when the polishing table 54 or 55 is
rotating, so that the area in the polishing pad, which makes
contact with the fixed brush, can be cleaned intensively.
Alternatively, the brush of the cleaning section 112 or 113 may be
moved such that it swings between the center and the edge of the
polishing pad so that the entire surface of the polishing pad can
be cleaned.
[0182] By such an expression as "intensively clean" is herein meant
(1) to clean a position or area for a longer time than the other
position or area, (2) when rubbing a polishing member with a brush,
a grindstone, a PVA sponge, or the like, to rub a position or area
at a higher pressure than the other position or area, (3) when
rubbing a polishing member with a rotating brush, grindstone, PVA
sponge, or the like, to rub a position or area at a higher
rotational speed than the other position or area, (4) when cleaning
off foreign matter by blowing a cleaning liquid, such as pure water
or a liquid chemical, onto a polishing member, to blow the cleaning
liquid onto a position or area at a higher flow rate, a higher
speed (higher pressure), a higher concentration and/or a high
temperature than the other position or area, (5) when sucking in a
slurry on a polishing member, to suck in the slurry on a position
or area at a high suction than the other position or area, (6) when
dissolving foreign matter on a polishing member with a solvent,
such peroxosulfuric acid or hydrofluoric acid, to apply the solvent
at a higher concentration or a higher temperature to a position or
area than the other position or area, (7) when cleaning a polishing
member by ultrasonic cleaning, to apply ultrasonic waves of higher
power to a position or area than the other position or area, etc.
This holds true for any other specifying method.
[0183] Wet-type wafer film thickness-measuring machines may be
installed in place of the polishing tables 56, 57. In this case, it
is possible to measure with the wafer film thickness-measuring
machine a thickness of a surface film of a semiconductor wafer
immediately after polishing, making it possible to additionally
polish the surface film of the semiconductor wafer or to control
the polishing process of the next semiconductor wafer by utilizing
the measured film thickness value.
[0184] In order to transfer a semiconductor wafer between the
polishing chamber and the area B, a rotary wafer station 98, having
reversing machines 99, 100, 101, 102 for reversing a semiconductor
wafer, is disposed at a position accessible by the transport robots
80, 81 and the top rings 52, 53. The reversing machines 99, 100,
101, 102 revolve by rotation of the rotary wafer station 98.
[0185] A semiconductor wafer is transferred between the polishing
chamber and the area B in the following manner: Assuming that the
reversing machines 99, 100, 101, 102, provided in the rotary wafer
station 98, are disposed as shown in FIG. 6, i.e., the reversing
machines 99, 100 are disposed on the area B side of the rotary
wafer station 98, the reversing machine 101 on the area C side and
the reversing machine 102 on the area D side, a semiconductor wafer
to be subjected to polishing is transferred by the transport robot
80 from the wafer station 70 to the reversing machine 99 disposed
on the area B side of the rotary wafer station 98. Another
semiconductor wafer is transferred by the transport robot 81 from
the wafer station 70 to the reversing machine 100 disposed on the
area B side of the rotary wafer station 98.
[0186] A shutter 45, provided in the partition 87, opens when the
transport robot 80 transports a semiconductor wafer to the rotary
wafer station 98 so that the semiconductor wafer can be transferred
between the area B and the polishing chamber. A shutter 46,
provided in the partition 87, opens when the transport robot 81
transports a semiconductor wafer to the rotary wafer station 98 so
that the semiconductor wafer can be transferred between the area B
and the polishing chamber.
[0187] After transferring the semiconductor wafer to the reversing
machine 99 and transferring the another semiconductor wafer to the
reversing machine 100, the rotary wafer station 98 is rotated on
its axis by 180 degrees to thereby move the reversing machine 99 to
the area D side and move the reversing machine 100 to the area C
side. The semiconductor wafer, which has been moved to the area C
side by the rotation of the rotary wafer station 98, is reversed by
the reversing machine 100 such that its upward surface to be
polished (front surface) turns downward, and then transferred to
the top ring 52. The semiconductor wafer, which has been moved to
the area D side by the rotation of the rotary wafer station 98, is
reversed by the reversing machine 99 such that its upward surface
to be polished (front surface) turns to downward, and then
transferred to the top ring 53.
[0188] The semiconductor wafers, which have been transferred to the
top rings 52, 53, are attracted to the top rings 52, 53 by their
vacuum attraction mechanisms. The semiconductor wafers, while kept
attracted to the top rings 52, 53, are transported to the polishing
tables 54, 55, and are polished with the polishing pads mounted on
the polishing tables 54, 55.
[0189] FIG. 7 is a schematic cross-sectional diagram illustrating
the top ring 52 and part of the polishing table 54 during
polishing. The top ring 53 and the polishing table 55 have the same
structures. As shown in FIG. 7, the top ring 52, which is a holder
for a semiconductor wafer 2 as a polishing object, comprises an air
bag 5 for pressing the semiconductor wafer 2 on a polishing member
(polishing pad) 10 at a predetermined pressure, a support section
(retainer ring) 14 provided such that it surrounds the polishing
object 2, and an air bag 6 for pressing the retainer ring 14 on a
surface of a polishing pad 10 around the semiconductor wafer 2 at a
predetermined pressure.
[0190] As shown in FIG. 7, the retainer ring 14 of this embodiment
is composed of a single member having a rectangular cross-sectional
shape and an annular plan shape extending along the circumference
of the semiconductor wafer 2, held by the top ring 2, with a slight
gap therebetween. The lower surface of the retainer ring 14 forms a
support surface for supporting the portion of the polishing pad 10
lying around the surface (to be polished) of the semiconductor
wafer 2, and is a flat surface, the entire surface being generally
on the same level. The retainer ring 14 may be formed of, for
example, a ceramic material such as zirconia or alumina, or an
engineering plastic material, such as an epoxy (EP) resin, a phenol
(PF) resin or a polyphenylene sulfide (PPS) resin.
[0191] The pressure of the retainer ring 14 against the polishing
pad 10 is adjusted by controlling the pressure in the air bag 6 by
a pressure adjustment mechanism 108. It is also possible not to
provide the airbag 6, and adjust the pressure of the support
surface of the retainer ring 14 by controlling the load, applied
from the shaft of the top ring 52, by the pressure adjustment
mechanism 108. The air bag 5 may be comprised of either a single
chamber, as illustrated in the Figure, or a plurality of concentric
chambers.
[0192] The polishing table 54 comprises a polishing platen 9 and
the polishing pad 10. The polishing pad 10 may be either a
single-layer pad, as shown in FIG. 7, or a multi-layer pad with two
or more layers. During polishing, the top ring 52, while pressing
the semiconductor wafer 2 on the polishing pad 10, rotates around
its shaft in the direction of arrow A. The polishing table 54 also
rotates around its shaft in the direction of arrow B during
polishing. The adhesion region specifying section 110 performs
detection of foreign matter on the polishing pad 10 during
polishing.
[0193] Returning to FIG. 6, the second polishing tables 56, 57 are
disposed respectively at positions accessible by the top rings 52,
53, so that semiconductor wafers, after completion of the polishing
in the first polishing tables 54, 55, can be polished with the
finishing polishing pads of the second polishing tables 54, 55.
Polishing of the respective semiconductor wafers in the finishing
tables is carried out by supplying pure water or a chemical
solution not containing abrasive grains, or a slurry to the
respective polishing pads, for example, SUBA 400 or Polytex (trade
names of polishing pads manufactured by Nitta Haas Incorporated).
During the polishing, semiconductor wafers to be subjected to the
next polishing may be transferred by the transport robots 81, 80 to
the reversing machines 101, 102 which have been moved to the area B
side.
[0194] The semiconductor wafers after completion of the polishing
are transferred by the top rings 52, 53 to the reversing machines
99, 100, respectively. After reversing the semiconductor wafers
with the reversing machines 99, 100 such that the front surfaces
after polishing (polished surfaces) turn to upward, the rotary
wafer station 98 is rotated by 180 degrees to thereby move the
semiconductor wafers to the area B side of the rotary wafer station
98. One of the semiconductor wafers, which have been moved to the
area B side, is transported by the transport robot 80 from the
reversing machine 99 to either the cleaning machine 82 or the wafer
station 70. The other semiconductor wafer is transported by the
transport robot 81 from the reversing machine 100 to either the
cleaning machine 83 or the wafer station 70. After carrying out
appropriate cleaning of the semiconductor wafers, the surface
(polished surface) of each semiconductor wafer is evaluated with
the adhesion region specifying section 120 to determine the
presence or absence of a scratch. Thereafter, the semiconductor
wafers are placed into the wafer cassette 21.
[0195] After the completion of polishing with the polishing table
54 or 55, the polishing pad attached on top of the polishing table
54 or 55 is dressed with the dresser 58 or 59. During dressing, the
abrasive liquid nozzle 60 or 61 supplies a cleaning liquid, such as
pure water, to the polishing pad. The dressing effects cleaning,
dressing, configuration correction, etc. of the surface of the
polishing pad. When adhesion of foreign matter to the polishing pad
is not detected by the adhesion region specifying section 110 or
111 and the adhesion region specifying section 120, an intensive
cleaning area in the polishing pad is intensively cleaned, e.g.,
with a brush of the cleaning section 112 or 113 in parallel with
the dressing. The intensive cleaning area is predetermined as an
area to which foreign matter is likely to adhere, as will be
described later. Accordingly, adhesion of foreign matter to the
polishing pad can be prevented by intensively cleaning the
intensive cleaning area of the polishing pad with the cleaning
section 112 or 113. The adhesion region specifying section 110 or
111 performs detection of foreign matter to the polishing pad also
during dressing. Therefore, adhesion of foreign matter to the
polishing pad can be detected and the adhesion area can be
specified also during dressing.
[0196] When foreign matter adhering to the polishing pad is
detected by the adhesion region specifying section 110 or 111
during polishing or during dressing, an annular area in the surface
of the polishing pad can be specified as the foreign matter
adhesion area in the polishing pad. It is to be noted in this
regard that the adhesion region specifying section 226 having the
displacement sensors 224, shown in FIGS. 3A and 3B, is employed in
this embodiment as the adhesion region specifying sections 110,
111. The displacement sensors 224 are disposed along a radial
direction of the polishing pad and each sensor 224 has an annular
detection area in the surface of the polishing pad when the
polishing pad is rotating. Thus, an annular area, corresponding to
the detection area of a particular displacement sensor 224 that has
detected foreign matter, can be specified as the foreign matter
adhesion area. After the foreign matter adhesion area is specified,
the foreign matter adhesion area is intensively cleaned with the
cleaning section 112 or 113, whereby the foreign matter adhering to
the polishing pad can be removed effectively. There is a fear that
the adhesion region specifying sections 110, 111, when in contact
with the polishing pad, might generate foreign matter. The adhesion
region specifying sections 110, 111 may therefore be located in a
not-shown retreat area during polishing a semiconductor wafer. The
adhesion region specifying sections 110, 111, when located in the
retreat area, may be cleaned with a not-shown adhesion region
specifying section cleaning apparatus. This can prevent generation
of foreign matter from the adhesion region specifying sections 110,
111.
[0197] There is a case where the adhesion region specifying
sections 110, 111 detect, besides foreign matter adhering to the
polishing pad, foreign matter moving on the polishing pad by a flow
of a slurry or a cleaning liquid. Therefore, in order to more
precisely detect adhesion of foreign matter to a polishing pad, the
chemical mechanical polishing apparatus, shown in FIG. 6, includes
the adhesion region specifying section 120 which evaluates the
presence or absence of a scratch in a surface (polished surface) of
a semiconductor wafer after polishing to detect adhesion of foreign
matter to the polishing pad. In this embodiment, the adhesion
region specifying section 254, which uses the photographic device
250, shown in FIG. 5, is employed as the adhesion region specifying
section 120. Thus, the adhesion region specifying section 120
evaluates the presence or absence of a scratch in a surface
(polished surface) of a semiconductor wafer after polishing by
making an image analysis of a shot image of the surface, shot by
the photographic device 250 (see FIG. 5), by the arithmetic unit
(evaluation device or image analyzer) 252. When the presence of a
scratch in the polished surface of the semiconductor wafer is
determined as a result of the image analysis, it means detection of
foreign matter to the polishing pad. Further, the foreign matter
adhesion area in the polishing pad can be specified by making
pattern recognition of a shot image of the scratch.
[0198] FIGS. 8A through 8E show scratch patterns as produced by a
polishing simulation, which are to be used as standard patterns in
image recognition. The simulation is carried out on the assumption
that: foreign matter, adhering to a polishing pad, lies on a circle
with a radius of R1, the center coinciding with the rotation center
of the polishing pad; the polishing pad is rotating at a speed of
90 rpm; and a semiconductor wafer being polished is rotating at a
speed of 80 rpm, without making a swinging movement during
polishing. Five standard patterns are produced with five different
radiuses R1 varying at an interval of 60 mm. In particular, FIG. 8A
shows a scratch pattern in the case where foreign matter, adhering
to the polishing pad, lies on a circle with a radius R1 of 315 mm,
FIG. 8B shows a scratch pattern in the case where foreign matter,
adhering to the polishing pad, lies on a circle with a radius R1 of
255 mm, FIG. 8C shows a scratch pattern in the case where foreign
matter, adhering to the polishing pad, lies on a circle with a
radius R1 of 195 mm, FIG. 8D shows a scratch pattern in the case
where foreign matter, adhering to the polishing pad, lies on a
circle with a radius R1 of 135 mm, and FIG. 8E shows a scratch
pattern in the case where foreign matter, adhering to the polishing
pad, lies on a circle with a radius R1 of 75 mm. It is preferred in
a practical operation to use more radiuses R1 with a shorter
interval so as to produce more standard patterns.
[0199] A pattern or patterns, similar to the shot scratch pattern,
are picked out by pattern recognition, and the foreign matter
adhesion area (range of a radius or radii of the pad) is specified
based on the similarity between the shot scratch pattern and the
standard patterns picked out. There is no need to make pattern
recognition when the absence of a scratch in the surface of the
semiconductor wafer is determined by the adhesion region specifying
section 120. In the case where the adhesion region specifying
section 120 has detected adhesion of foreign matter to the
polishing pad and specified the foreign matter adhesion area, the
foreign matter adhesion area in the polishing pad is intensively
cleaned with the cleaning section 112 or 113. This can effectively
remove the foreign matter from the polishing pad.
[0200] When a foreign matter adhesion area in a polishing pad,
specified by the adhesion region specifying section 110 or 111,
overlaps with a foreign matter adhesion area in the polishing pad,
specified by the adhesion region specifying section 120, the
probability of adhesion of foreign matter to the polishing pad is
high, and the foreign matter is present in the specified foreign
matter adhesion area with high probability. In case foreign matter
cannot be removed during a polishing process for one semiconductor
wafer and the foreign matter is detected in a plurality of wafers
in spite of intensive cleaning of the foreign matter adhesion area
of the polishing pad, polishing with the polishing table having
foreign matter may be stopped and the foreign matter adhesion area
may be intensively cleaned with the cleaning section 112 or 113.
The removal of the foreign matter from the polishing pad can be
detected with the adhesion region specifying section 110 or
111.
[0201] The chemical mechanical polishing apparatus can store data
on foreign matter adhesion areas, specified by the adhesion region
specifying section 110 or 111 and the adhesion region specifying
section 120, in a storage device installed in a control computer
130. An area in the polishing pad, to which foreign matter is
likely to adhere, can be determined by calculation of an adhesion
probability with the control computer 130 based on the stored data
on specified foreign matter adhesion areas. By predetermining an
area, to which foreign matter is likely to adhere, as an intensive
cleaning area, and intensively cleaning the area, when there is no
foreign matter in the area, with the cleaning section 112 or 113,
adhesion of foreign matter to the polishing pad can be prevented
effectively. In the chemical mechanical polishing apparatus, the
entire process, including transport, polishing and cleaning of a
semiconductor wafer, detection of adhesion of foreign matter to the
polishing pad and specification of a foreign matter adhesion
position or a foreign matter adhesion area, is controlled by the
control computer 130.
[0202] A description will now be given of a method for calculating
the probability of adhesion of foreign matter to the polishing pad
10 of the polishing table 54 based on stored data on foreign matter
adhesion areas specified by the adhesion region specifying section
110. First, the polishing pad 10 of the polishing table 54 is
divided to define 5 concentric annular zones 1 to 5, as shown in
FIG. 9A. The respective zones correspond to the detection areas of
the 5 displacement sensors 224 of the adhesion region specifying
section 110. An overlapping area between adjacent sensor detection
areas is included in the inner zone. Assuming that the data on
specified area is stores as adhesion frequencies in the zones 1 to
5, as shown in FIG. 9B, the adhesion probabilities in the zones
will be calculated as shown in FIG. 9C (adhesion probability in a
zone (%)=adhesion frequency in the zone/the total
frequency.times.100).
[0203] If a zone or zones with an adhesion probability of not less
than 30% are to be designated as an intensive cleaning area, then
the zones 3 and 4 will be designated as an intensive cleaning area.
When intensively cleaning the intensive cleaning area of the
polishing pad 10 with the cleaning section 112, the polishing pad
10 is cleaned while swinging the brush of the cleaning 112 over the
width of the zones 3 and 4. If a zone with the highest adhesion
probability is to be designated as an intensive cleaning area, the
zone 3 is the intensive cleaning area of the polishing pad 10. In
this case, there is no need for the calculation of adhesion
probability and the zone with the highest adhesion frequency can be
designated as an intensive cleaning area. When intensively cleaning
the intensive cleaning area (zone 3) of the polishing pad 10 with
the cleaning section 112, the brush of the cleaning section 112 is
allowed to swing over the width of the zone 3 during cleaning. In
the case where the brush is large enough to clean the zone 3 of the
polishing pad 10 without swinging, the brush may be kept at a fixed
position during cleaning.
[0204] While the method for calculating the probability of adhesion
of foreign matter to the polishing pad 10 of the polishing table
54, based on stored data on adhesion are as specified by the
adhesion region specifying section 110, has been described, the
same method applies to the case of calculating adhesion probability
for the polishing pad of the polishing table 55 based on stored
data on adhesion are as specified by the adhesion region specifying
section 111. Also in the case of calculating adhesion probability
based on an adhesion area specified by the adhesion region
specifying section 120, the probability can be calculated in the
same manner, i.e., by defining divisional annular zones in the
surface of the polishing pad, storing adhesion frequencies in the
zones in the storage device, and calculating the adhesion
probabilities from the stored data.
[0205] Next, a description will now be given of a control flow in a
process of polishing a semiconductor wafer as a polishing object
with a polishing pad as a polishing member, using the chemical
mechanical polishing apparatus shown in FIG. 6. For simplicity of
description, the following description illustrates the case of
polishing a semiconductor wafer, which has been taken out of the
wafer cassette 21, with the polishing pad 10 of the polishing table
54, followed by cleaning, and returning the semiconductor wafer to
the wafer cassette 21, and thereafter starting processing of the
next semiconductor wafer. In a practical process, a plurality of
semiconductor wafers will be processed in parallel in view of the
throughput.
[0206] The following information, for example, is stored in the
storage device of the control computer 130:
A. Polishing Apparatus Control Program
[0207] A-1. Main routine for polishing
[0208] A-2. Routine for determination of completion of preparations
for polishing
[0209] A-3. Dressing routine
[0210] A-4. Polishing pad cleaning routine
[0211] A-5. Semiconductor wafer cleaning routine
[0212] A-6. Routine for monitoring foreign matter adhesion by
evaluation of polishing pad
[0213] A-7. Routine for determination of foreign matter adhesion by
evaluation of polished surface
[0214] A-8. Intensive cleaning area calculation routine
[0215] A-9. Semiconductor wafer transport routine [0216] etc.
B. Various Conditions
[0217] B-1. Semiconductor wafer transport conditions
[0218] B-2. Polishing conditions (polishing recipe) [0219] B-2-1.
Rotational speed of polishing pad [0220] B-2-2. Rotational speed of
semiconductor wafer (top ring) [0221] B-2-3. Swinging speed of
semiconductor wafer (top ring) [0222] B-2-4. Swinging range of
semiconductor wafer (top ring) [0223] B-2-5. Polishing time [0224]
B-2-6. Polishing pressure [0225] B-2-7. Flow rate of slurry
supplied
[0226] B-3. Dressing conditions [0227] B-3-1. Rotational speed of
polishing pad [0228] B-3-2. Rotational speed of dresser [0229]
B-3-3. Swinging speed of dresser [0230] B-3-4. Swinging range of
dresser [0231] B-3-5. Dressing time [0232] B-3-6. Dressing pressure
[0233] B-3-7. Flow rate of cleaning liquid supplied
[0234] B-4. Semiconductor wafer cleaning conditions
[0235] B-5. Polishing pad cleaning conditions [0236] B-5-1. Normal
cleaning conditions [0237] B-5-1-1. Rotational speed of brush
[0238] B-5-1-2. Swinging speed of brush [0239] B-5-1-3. Swinging
range of brush [0240] B-5-1-4. Pressure of brush [0241] B-5-1-5.
Cleaning time [0242] B-5-2. Intensive cleaning conditions [0243]
B-5-2-1. Rotational speed of brush [0244] B-5-2-2. Pressure of
brush [0245] B-5-2-3. Cleaning time
[0246] B-6. Geometric parameters [0247] B-6-1. Diameter of
semiconductor wafer [0248] B-6-2. Coordinates of rotation center of
polishing pad [0249] B-6-3. Coordinates of rotation center of top
ring [0250] B-6-4. Coordinates of pivot center of top ring [0251]
B-6-5. Radius of pivoting of top ring
[0252] B-7. Intensive cleaning area
[0253] etc.
C. Information on Foreign Matter Adhesion
[0254] C-1. Polishing pad zones [0255] C-2. Standard patterns for
image recognition [0256] C-3. Foreign matter adhesion region [0257]
C-4. Intensive cleaning area etc.
[0258] Polishing by the polishing apparatus is started when the
control computer 130 retrieves a polishing apparatus control
program from the storage device, and polishing proceeds, e.g., in
accordance with the main routine for polishing shown in FIG. 10. In
particular, the control computer 130 first reads various conditions
from the storage device installed as part of the computer 130. The
various conditions stored in the storage device include
semiconductor wafer (polishing object) transport conditions,
polishing conditions (polishing recipe), dressing conditions,
semiconductor wafer cleaning conditions, polishing pad (polishing
member) cleaning conditions, geometric parameters, intensive
cleaning area, etc. In addition to the various conditions, the
polishing apparatus control program and information on foreign
matter adhesion are stored in the storage device. The above
information may be stored in an external storage device separate
from the control computer 130. In this case, the control computer
130 reads the above information from the external storage device,
e.g., by an input device installed in the control computer 130 in
advance of polishing, and stores the information in the storage
device installed as part of the control computer 130.
[0259] After reading the various conditions from the storage
device, the control computer 130 produces, based on the read
various conditions, standard patterns for image recognition, which
are to be used in specification of a foreign matter adhesion area,
by evaluation of the polished surface of a polishing object with
the adhesion region specifying section 120. The standard patterns
to be produced may be, for example, data on a radial density
distribution or a circumferential density distribution of
scratches, or data on the presence or absence of a scratch at a
specified position on a polished surface, analyzed from data on a
track of foreign matter as shown in FIGS. 8A through 8E. The
control computer 130 stores the produced standard patterns in the
storage device. The foreign matter track data can be produced in
the manner described above.
[0260] Next, the control computer 130 so controls the polishing
apparatus that a semiconductor wafer is taken by the transport
robot 24 out of the wafer cassette 21 and transported to the
support 28. After the semiconductor wafer is transported to the
support 28, the control computer 130 so controls the transport
robot 81, etc. as to transport the semiconductor wafer to the
reversing device 100 provided in the rotary wafer station 98.
[0261] After the semiconductor wafer is transported to the
reversing device 100, the control computer 130 executes the routine
for determination of the completion of preparations for polishing,
shown in FIG. 11. In the routine for determination of the
completion of preparations for polishing, a dressing flag which is
ON during dressing, a foreign matter adhesion flag which is ON when
foreign matter is adhering to a polishing pad, and a cleaning flag
which is ON during cleaning of a polishing pad, are referred to.
When at least one flag is ON, the next processing is awaited,
whereas when all the flags are turned OFF, a termination flag of
foreign matter adhesion monitoring by evaluation of polishing pad
is turned ON, thereby terminating the routine for determination of
the completion of preparations for polishing. Preparations for
polishing of the semiconductor wafer with the polishing pad 10 of
the polishing table 54 are now complete. When the termination flag
of foreign matter adhesion monitoring by evaluation of polishing
pad is turned ON, the control computer 130 terminates monitoring of
foreign matter on the surface of the polishing pad 10 with the
adhesion region specifying section 110 and retreats the adhesion
region specifying section 110 to the retreat area.
[0262] Next, the control computer 130 so controls the polishing
apparatus as to rotate the rotary wafer station 98 and reverse the
semiconductor wafer with the reversing device 100 and, after
transporting the semiconductor wafer to the top ring 52, transport
it to the polishing table 54. After the semiconductor wafer is
transported to the polishing table 54, the control computer 130 so
controls the polishing apparatus as to polish the semiconductor
wafer under the polishing conditions read from the storage device.
The semiconductor wafer polishing conditions include the rotational
speed of the polishing pad, the rotational speed of the
semiconductor wafer (top ring), the swinging speed of the
semiconductor wafer (top ring), the swinging range of the
semiconductor wafer (top ring), the polishing time, the polishing
pressure, the flow rate of a slurry supplied, etc.
[0263] On completion of the polishing of the semiconductor wafer,
the control computer 130 executes the following two lines of
processes in parallel: a line in which the semiconductor wafer is
cleaned and dried, and then returned to the wafer cassette 21; and
a line in which the polishing pad 10 is dressed and cleaned to
prepare for the next polishing.
[0264] A description will be made first of the process line for
dressing and cleaning the polishing pad to prepare for the next
polishing. This line of process comprises three operations the
operation of dressing the polishing pad; the operation of cleaning
the polishing pad; and the operation of monitoring adhesion of
foreign matter to the surface of the polishing pad. On completion
of the polishing of the semiconductor wafer, the control computer
130 executes the dressing routine shown in FIG. 12, the polishing
pad cleaning routine shown in FIG. 13, and the routine for
monitoring foreign matter adhesion by evaluation of the polishing
pad shown in FIG. 14 in parallel.
[0265] The dressing routine shown in FIG. 12 is described first. In
the dressing routine, the control computer 130 turns a dressing
flag ON, indicating that the polishing pad 10 is being dressed, and
so controls the polishing apparatus as to dress the polishing pad
10 with the dresser 58 under the dressing conditions which have
been read by the computer from the storage device at the start of
the polishing process. The dressing conditions include the
rotational speed of the polishing pad, the rotational speed of the
dresser, the swinging speed of the dresser, the swinging range of
the dresser, the dressing time, the dressing pressure, the flow
rate of a cleaning liquid supplied, etc. On completion of the
dressing of the polishing pad 10, the control computer 130 turns
the dressing flag OFF, thereby terminating the dressing
routine.
[0266] The polishing pad cleaning routine shown in FIG. 13 will now
be described. In the polishing pad cleaning routine, the control
computer 130 first turns a cleaning flag ON, indicating that the
polishing pad 10 is being cleaned. Next, according to this
embodiment, the control computer 130 determines whether the
semiconductor wafer after polishing is a 3nth wafer (n=1, 2, 3 . .
. ) or not.
[0267] In the case where the semiconductor wafer after polishing is
not 3nth, the control computer 130 so controls the polishing
apparatus as to evenly clean the entire polishing pad 10 with the
brush of the cleaning section 112 under the normal cleaning
conditions which have been read by the computer from the storage
device at the start of the polishing process. The normal cleaning
conditions include the rotational speed of the brush, the swinging
speed of the brush, the swinging range of the brush, the pressure
of the brush, the cleaning time, etc. The rotational speed of the
polishing pad during the cleaning is also the rotational speed of
the polishing pad during its dressing which is carried out in
parallel with the cleaning. In the case where the semiconductor
wafer after polishing is 3nth, the control computer 130 reads an
intensive cleaning area of the polishing pad 10 from the storage
device, and so controls the polishing apparatus as to intensively
clean the intensive cleaning area with the brush of the cleaning
section 112. The intensive cleaning area is an intensive cleaning
area which has been stored in the storage device prior to
polishing, and/or an intensive cleaning area which has been stored
in the storage device in the below-described intensive cleaning
area calculation routine. In this embodiment, the intensive
cleaning area is stored as the zone number(s) of one or more of the
5 ring-shaped divisional zones of the polishing pad 10, shown in
FIG. 9A. The cleaning conditions are those intensive cleaning
conditions which have been read by the computer from the storage
device at the start of polishing. The intensive cleaning conditions
include the rotational speed of the brush, the pressure of the
brush, the cleaning time, etc. The rotational speed of the
polishing pad during the intensive cleaning is also the rotational
speed of the polishing pad during its dressing routine which is
carried out in parallel with the cleaning.
[0268] The polishing apparatus of this embodiment employs, as the
brush of the cleaning section 112, a brush having a diameter which
is larger than the width of the intensive cleaning area.
Accordingly, by appropriately setting the position of the brush of
the cleaning section 112 based on the intensive cleaning area that
the control computer 130 has read from the storage device, the
intensive cleaning area of the polishing pad 10 can be intensively
cleaned without swinging the brush. The position of the brush of
the cleaning section 112 is set by the control computer 130 as the
coordinates of the center of the brush such that the distance of
the brush center from the rotation center of the polishing table 54
takes an intermediate value between the inside radius and the
outside radius of the zone designated as the intensive cleaning
area. It is also possible to pre-store such positions of the brush
in the storage device that each of the 5 zones shown in FIG. 9A can
be cleaned intensively. On completion of the cleaning of the
polishing pad 10, the control computer 130 turns the cleaning flag
OFF, thereby terminating the polishing pad cleaning routine.
[0269] A description will now be given of the routine for
monitoring foreign matter adhesion by evaluation of the polishing
pad, shown in FIG. 14. In the routine for monitoring foreign matter
adhesion by evaluation of the polishing pad, the control computer
130 first turns the termination flag of foreign matter adhesion
monitoring by evaluation of polishing pad OFF. The control computer
130 then moves the adhesion region specifying section 110 to the
polishing pad monitoring area where the adhesion region specifying
section 110 monitors adhesion of foreign matter to the polishing
pad 10.
[0270] The control computer 130 monitors signals from the adhesion
region specifying section 110 while the termination flag of foreign
matter adhesion monitoring by evaluation of polishing pad is OFF.
When foreign matter adheres to the surface of the polishing pad 10,
a peak P, as shown in FIG. 3C, will appear in a signal from the
adhesion region specifying section 110. The control computer 130
analyzes signals from the adhesion region specifying section 110
and determines adhesion of foreign matter to the polishing pad 10
by detection of such a peak P. The control computer 130, however,
does not determine adhesion of foreign matter only by one-time
detection of a peak P because of the possibility of foreign matter,
moving over the surface of the polishing pad 10 along with a
cleaning liquid, having been detected. In this embodiment,
therefore, the control computer 130 determines adhesion of foreign
matter to the polishing pad 10 when a displacement sensor 224,
which detected a peak P, has again detected the peak P after one
rotation of the polishing pad 10.
[0271] When the control computer 130 has determined adhesion of
foreign matter to the polishing pad 10, the control computer 130
turns a foreign matter adhesion flag ON. The foreign matter
adhesion flag is ON while foreign matter remains adhering to the
polishing pad 10, i.e., while a displacement sensor 224, with which
a peak P has been detected, keeps sending a signal with the peak P
appearing repeatedly in synchronization with the rotating cycles of
the polishing pad.
[0272] After turning the foreign matter adhesion flag ON, the
control computer 130 specifies a foreign matter adhesion area. In
this embodiment, a foreign matter adhesion area corresponds to the
detection area of the displacement sensor 224 with which the peak P
has been detected (see FIG. 9A). Thereafter, the control computer
130 so controls the polishing apparatus as to intensively clean the
specified foreign matter adhesion area with the cleaning section
112. The polishing pad cleaning routine, which is in execution in
parallel with the present routine, is stopped during the intensive
cleaning. The intensive cleaning conditions are those which were
read by the control computer 130 from the storage device at the
start of the polishing process. The intensive cleaning conditions
include the rotational speed of the brush, the pressure of the
brush, the cleaning time, etc. The rotational speed of the
polishing pad during the intensive cleaning is also the rotational
speed of the polishing pad during dressing routine which is carried
out in parallel with the intensive cleaning.
[0273] In the polishing apparatus of this embodiment, the brush of
the cleaning section 112 has a diameter which is larger than the
width of the intensive cleaning area. Accordingly, by appropriately
setting the position of the brush based on the specified foreign
matter adhesion area, the foreign matter adhesion area can be
intensively cleaned without swinging the brush. The position of the
brush is set by the control computer 130 as the coordinates of the
center of the brush such that the distance of the brush center from
the rotation center of the polishing table 54 takes an intermediate
value between the inside radius and the outside radius of the
ring-shaped zone designated as the foreign matter adhesion area. It
is also possible to pre-store such positions of the brush in the
storage device that each of the 5 zones shown in FIG. 9A can be
cleaned intensively. In the polishing apparatus of this embodiment,
the same divisional zones of polishing pad are employed both f or
the intensive cleaning area and for the foreign matter adhesion
area. Accordingly, a common position of the brush may be pre-stored
in the storage device.
[0274] After cleaning the specified foreign matter adhesion area
with the brush of the cleaning section 112 for the cleaning time
set in the intensive cleaning conditions, the control computer 130
again determines the presence or absence of foreign matter. In the
case where foreign matter, adhering to the polishing pad 10, still
exists, the above processing is repeated. In the case where there
is no foreign matter adhering to the polishing pad 10, the foreign
matter adhesion flag is turned OFF, and the polishing pad cleaning
routine is resumed. If the determination is made past a cleaning
termination time as scheduled in the polishing pad cleaning
routine, the control computer 130 immediately executes processing
for the termination of the polishing pad cleaning routine.
[0275] When the termination flag of foreign matter adhesion
monitoring by evaluation of polishing pad is turned ON, the control
computer 130 moves the adhesion region specifying section 110 to
the retreat area, thereby terminating the routine for monitoring
foreign matter adhesion by evaluation of the polishing pad.
[0276] The termination flag of foreign matter adhesion monitoring
by evaluation of polishing pad is not turned ON while the foreign
matter adhesion flag is ON, as shown in FIG. 11, and thus the
routine for monitoring foreign matter adhesion by evaluation of the
polishing pad does not end. Further, polishing of the next
semiconductor wafer is not started. Therefore, when foreign matter
on the polishing pad 10 cannot be removed in spite of intensive
cleaning of the foreign matter adhesion area carried out
repeatedly, an alarm may be issued to stop the polishing apparatus.
This enables a person in charge of maintenance of the polishing
apparatus to take action, such as replacement of the polishing
pad.
[0277] In parallel with the cleaning of the specified foreign
matter adhesion area, the control computer 130 makes the
calculation of intensive cleaning area. In the intensive cleaning
area calculation routine, as shown in FIG. 16, the control computer
130 stores the specified foreign matter adhesion area in the
storage device, reads stored foreign matter adhesion areas from the
storage device, and then calculates an intensive cleaning area. In
this embodiment, the control computer 130 counts the frequency of
foreign matter adhesion in the respective foreign matter adhesion
areas and designates a zone of the highest frequency of foreign
matter adhesion as an intensive cleaning area. The calculated
intensive cleaning area is finally stored in the storage device.
Instead of calculating an intensive cleaning area from stored
foreign matter adhesion areas, it is also possible to pre-count the
frequency of foreign matter adhesion for each zone of a polishing
pad and record the data in a storage area and, when a foreign
matter adhesion area is specified, add 1 to the count of the zone
(area). In this calculation method, a zone of the highest count is
designated as an intensive cleaning area. This method can shorten
the processing time.
[0278] When foreign matter, which has not been removed from the
polishing pad 10 after intensive cleaning, is detected again, the
intensive cleaning area calculation routine is not executed in
order to avoid double counting. Whether detection of particular
foreign matter is re-detection of the same foreign matter or not is
determined by whether or not a peak P in a signal from the relevant
displacement sensor 224 appears periodically in synchronization
with the rotation of the polishing pad.
[0279] Returning to the main routine for polishing shown in FIG.
10, a description will be given below of the process line of
cleaning and drying the semiconductor wafer and then returning the
wafer to the cassette 21. On completion of the polishing of the
semiconductor wafer, the control computer 130 controls the
transport robot 81, etc. to transport the semiconductor wafer from
the polishing table 54 to the cleaning device 83. The control
computer 130 then so controls the polishing apparatus that after
cleaning the semiconductor wafer with the cleaning device 83, the
transport robot 81 transports the semiconductor wafer to the
cleaning device 26, where the semiconductor wafer is cleaned and
dried.
[0280] On completion of the cleaning and drying of the
semiconductor wafer with the cleaning device 26, the control
computer 130 so controls the polishing apparatus as to transport
the semiconductor wafer by the transport robot 81 from the cleaning
device 26 to the support 28, and then transport the semiconductor
wafer by the transport robot 24 to the adhesion region specifying
section 120.
[0281] After the semiconductor wafer has been transported to the
adhesion region specifying section 120, the control computer 130
executes a routine for determination of foreign matter adhesion by
evaluation of the polished surface of the semiconductor wafer
(polishing object) to carry out determination of adhesion of
foreign matter to the surface of the polishing pad (polishing
member) and specification of a foreign matter adhesion area. In the
routine for determination of foreign matter adhesion by evaluation
of the polished surface, the control computer 130 executes the
steps shown in FIG. 15.
[0282] The control computer 130 first executes shooting the
polished surface of the semiconductor wafer with the adhesion
region specifying section 120 and taking in the image data.
Corrections, such as denoising, sharpening, binarization, etc. of
the taken image data and line extraction of the corrected image
data are then performed. Thereafter, in order to determine whether
an extracted line is a scratch or not, the control computer 130
executes pattern recognition. In the pattern recognition, a
determination is made as to whether an extracted line is a scratch
or not based on the length, the shape, etc. of the extracted line.
If the absence of a scratch in the polished surface is determined,
then the control computer 130 terminates the routine for
determination of foreign matter adhesion by evaluation of the
polished surface.
[0283] If the presence of a scratch in the polished surface is
determined, the control computer 130 analyzes the particular image
data from which the line, determined as the scratch, is extracted,
and specifies a radial density distribution or a circumferential
density distribution of the scratch, the presence or absence of the
scratch at a specified position on the polished surface, etc. as a
detection pattern. Thereafter, the control computer 130 determines
a standard pattern which is most similar to the detection pattern
by the nearest neighbor method, and specifies the foreign matter
adhesion area (distance of the foreign matter from the center of
the polishing pad), corresponding to the standard pattern, as the
foreign matter adhesion area in the surface of the polishing pad
(polishing member).
[0284] Next, the control computer 130 determines to which zone of
the 5 zones shown in FIG. 9A the specified foreign matter adhesion
area corresponds. If the determined zone coincides with the foreign
matter adhesion area specified by the evaluation of the polishing
pad, the control computer 130 terminates the foreign matter
adhesion determination routine by evaluation of the polished
surface. If the determined zone does not coincide with the foreign
matter adhesion region specified by the evaluation of the polishing
pad, or in the case where the evaluation of the polishing pad has
not detected any foreign matter, the control computer 130 turns the
foreign matter adhesion flag ON, and so controls the polishing
apparatus as to intensively clean the specified foreign matter
adhesion area of the polishing pad with the cleaning section 112.
The cleaning conditions are those intensive cleaning conditions
which were read by the control computer 130 from the storage device
at the start of the polishing process. The intensive cleaning
conditions include the rotational speed of the brush, the pressure
of the brush, the cleaning time, etc. The rotational speed of the
polishing pad in the intensive cleaning is also the rotational
speed of the polishing pad in the dressing routine.
[0285] If the polishing pad cleaning routine is in execution when
the intensive cleaning is about to start, the polishing pad
cleaning routine is stopped. If the intensive cleaning in the
routine for monitoring foreign matter adhesion by evaluation of the
polishing pad is in execution, the intensive cleaning in the
present routine is waited until completion of the intensive
cleaning in the routine for monitoring foreign matter adhesion by
evaluation of the polishing pad.
[0286] In this embodiment, the brush of the cleaning section 112
has a diameter which is sufficiently larger than the width of the
annular foreign matter adhesion area, corresponding to the standard
pattern, of the polishing pad. Accordingly, by appropriately
setting the position of the brush based on the specified foreign
matter adhesion area, the foreign matter adhesion area can be
intensively cleaned without swinging the brush. The position of the
brush is set as the coordinates of the center of the brush by the
control computer 130 such that the distance of the brush center
from the rotation center of the polishing table 54 coincides with
the specified foreign matter adhesion area corresponding to the
standard pattern.
[0287] After carrying out cleaning of the specified foreign matter
adhesion area with the cleaning section 112 for the cleaning time
set in the read intensive cleaning conditions, the control computer
130 turns the foreign matter adhesion flag OFF to terminate the
routine for determination of foreign matter adhesion by evaluation
of the polished surface. If the polishing pad cleaning routine has
been suspended, the polishing pad cleaning routine is resumed. If,
however, a cleaning termination time as scheduled in the polishing
pad cleaning routine is past, the control computer 130 immediately
executes processing for the termination of the polishing pad
cleaning routine.
[0288] In parallel with the intensive cleaning of the foreign
matter adhesion area with the cleaning section 112, the control
computer 130 executes the intensive cleaning area calculation
routine in the manner described above. In the calculation of an
intensive cleaning area, stored data on zones specified as foreign
matter adhesion areas in the above-described manner is utilized to
determine an intensive cleaning area. Alternatively, it is possible
to store foreign matter adhesion areas as specified by pattern
recognition.
[0289] Returning to the main routine for polishing shown in FIG.
10, on completion of the routine for determination of foreign
matter adhesion by evaluation of the polished surface, the control
computer 130 so controls the transport robot 24, etc. as to take
the semiconductor wafer out of the adhesion region specifying
section 120 and transport the semiconductor wafer to the wafer
cassette 21. Even in the case where in the routine for
determination of foreign matter adhesion by the evaluation of the
polished surface, the presence of a scratch is determined and a
foreign matter adhesion area specified in that routine differs from
a foreign matter adhesion area specified by the evaluation of the
polishing pad, and the former foreign matter adhesion area is
subjected to intensive cleaning, the control computer 130, while
turning the foreign matter adhesion flag ON, can so control the
transport robot 24, etc. as to take the semiconductor wafer out of
the adhesion region specifying section 120 and transport the
semiconductor wafer to the wafer cassette 21. The control computer
130 determines whether processing of a predetermined number of
semiconductor wafers is complete. If not complete, the control
computer 130 so controls the polishing apparatus as to start
processing of the next semiconductor wafer.
[0290] While the present invention has been described in terms of
the preferred embodiments mainly with reference to FIG. 6 and FIGS.
10 through 16, the embodiments, of course, are not limiting of the
scope of the present invention.
[0291] Though the above-described chemical mechanical polishing
apparatus employs as the adhesion region specifying sections 110,
111 the adhesion region specifying section 226 shown in FIGS. 3A
and 3B, which evaluates a polishing pad (polishing member) by a
contact method using the displacement sensors 224, it is also
possible to employ as the adhesion region specifying sections 110,
111 the adhesion region specifying section 206 shown in FIGS. 2A
and 2B, which evaluates a polishing member by a contact method
using the pressure sensors 204, or the adhesion region specifying
section 234 shown in FIG. 4, which evaluates a polishing member by
a non-contact method using the photographic device 230.
[0292] Though the above-described chemical mechanical polishing
apparatus has both the adhesion region specifying sections 110, 111
which directly detect foreign matter on a polishing member
(polishing pad) and the adhesion region specifying section 120
which detects foreign matter on a polishing member (polishing pad)
indirectly by evaluation of the surface (polished surface) of a
polishing object (semiconductor wafer) after polishing, a chemical
mechanical polishing apparatus according to the present invention
may have only one of the two types of adhesion region specifying
sections. Further, a chemical mechanical polishing apparatus
according to the present invention may not be provided with an
adhesion region specifying section, but provided with a control
section which reads information from a storage medium storing
information on an intensive cleaning position or an intensive
cleaning area in the surface of a polishing member, and so controls
the above-described cleaning section as to intensively clean the
intensive cleaning position or the intensive cleaning area in the
surface of the polishing member. The intensive cleaning of the
intensive cleaning position or the intensive cleaning area can
prevent adhesion of foreign matter to the surface of the polishing
pad.
[0293] Though the entire process is controlled by the single
control computer 130 in the above-described chemical mechanical
polishing apparatus, it is also possible to provide an independent
control section for an adhesion region specifying section. In this
case, a control section for controlling the entire chemical
mechanical polishing apparatus and the control section for
controlling the adhesion region specifying section will be able to
communicate with each other so that the control sections can
cooperate with each other in performing a polishing process.
Further in this case, a specified foreign matter adhesion area may
be stored in a storage device provided in the adhesion region
specifying section.
[0294] FIG. 17 is a systematic diagram of an adhesion region
specifying apparatus, which is a variation of the above-described
adhesion region specifying section 120, adapted to be independent
of the polishing apparatus. The adhesion region specifying
apparatus includes a central processing unit (arithmetic unit) 140,
a main memory 142, a storage device 144, an input device (reading
device) 146 and an output device 148, which function in cooperation
with each other.
[0295] The following information, for example, is stored in the
storage device 144:
A. Adhesion Region Specifying Apparatus Control Program
[0296] A-1. Various conditions reading routine
[0297] A-2. Standard pattern production routine
[0298] A-3. Image reading routine
[0299] A-4. Image analysis routine
[0300] A-5. Foreign matter adhesion area display routine [0301]
etc.
B. Various Conditions
[0302] B-1. Polishing conditions (polishing recipe) [0303] B-1-1.
Rotational speed of polishing pad [0304] B-1-2. Rotational speed of
semiconductor wafer (top ring) [0305] B-1-3. Swinging speed of
semiconductor wafer (top ring) [0306] B-1-4. Swinging range of
semiconductor wafer (top ring) [0307] B-1-5. Polishing time
[0308] B-2. Geometric parameters [0309] B-2-1. Diameter of
semiconductor wafer [0310] B-2-2. Coordinates of rotation center of
polishing pad [0311] B-2-3. Coordinates of rotation center of top
ring [0312] B-2-4. Coordinates of pivot center of top ring [0313]
B-2-5. Radius of pivoting of top ring [0314] etc.
C. Information on Foreign Matter Adhesion
[0315] C-1. Standard patterns for image recognition
[0316] C-2. Shot image of polished surface [0317] etc.
[0318] A method for specifying a foreign matter adhesion area in a
surface of a polishing member, such as a polishing pad, from a
polished surface of a polishing object, such as a semiconductor
wafer, with a scratch, caused by the foreign matter on the
polishing member, formed in the polished surface, by using the
adhesion region specifying apparatus, will now be described with
reference to the flow of a process for specifying a foreign matter
adhesion area, shown in FIG. 18.
[0319] First, upon input of a command to start the process from an
input device, such as a keyboard, a mouse, touch panel, etc., the
central processing unit (arithmetic unit) 140 receives a command of
a control program stored in the main memory 142 and reads various
conditions from the storage device 144. As described above,
polishing conditions (polishing recipe), geometric parameters, etc.
are stored as various conditions in the storage device 144.
[0320] In the case where the polishing object is a semiconductor
wafer and the polishing apparatus is one as shown in FIG. 7,
including a top ring and a polishing table with a polishing pad,
the polishing conditions (polishing recipe) include the rotational
speed of the polishing pad, the rotational speed of the
semiconductor wafer (top ring), the swinging speed of the
semiconductor wafer (top ring), the swinging range of the
semiconductor wafer (top ring), the polishing time, etc. The
geometric parameters include the diameter of the semiconductor
wafer, the coordinates of the rotation center of the polishing pad,
the coordinates of the rotation center of the top ring, the
coordinates of the pivot center of the top ring, the radius of
pivoting of the top ring, etc.
[0321] The various conditions are read in the storage device 144
from the polishing apparatus or an external storage device using
the input device (reading device) 146 installed in the adhesion
region specifying apparatus, or inputted to the storage device 144
manually from an input device, such as a keyboard, a mouse or a
touch panel, prior to the process for specifying a foreign matter
adhesion area. Besides the various conditions, a control program
for the adhesion region specifying apparatus and information on
foreign matter adhesion are also stored in the storage device
144.
[0322] After reading the various conditions from the storage device
144, the central processing unit 140, on receipt of a command of
the control program in the main memory 142, produces standard
patterns for image recognition, which are to be used in specifying
a foreign matter adhesion area, based on the read various
conditions, and stores the produced standard patterns as
information on foreign matter adhesion in the storage device 144.
The standard patterns are, for example, data on tracks of foreign
matter as shown in FIGS. 8A through 8E. Such data on tracks of
foreign matter can be produced in the manner described above.
[0323] Next, the central processing unit 140, on receipt of a
command of the control program in the main memory 142, reads a shot
image of a polished surface with a scratch or scratches. The
central processing unit 140 may either read the shot image from a
photographic device using the input device (reading device) 146 or
read the shot image from an external storage medium, such as a
floppy disk or a CD-ROM. Alternatively, the central processing unit
140 may read the shot image of a polished surface, pre-stored in
the storage device of the adhesion region specifying apparatus.
[0324] Next, the central processing unit 144, on receipt of a
command of the control program in the main memory 142, performs
corrections (image transformation), such as denoising, sharpening,
binarization, etc., on the read image data and line extraction
(feature extraction) on the corrected image data. Thereafter, the
central processing unit 140, on receipt of a command of the control
program in the main memory 142, executes pattern recognition (image
recognition) to extract a scratch from extracted lines.
[0325] Next, the central processing unit 140, on receipt of a
command of the control program in the main memory 142, designates
an image data, from which the scratch is extracted, as a detection
pattern and determines by image recognition a standard pattern
which is most similar to the detection pattern, and specifies the
foreign matter adhesion area (distance of foreign matter from the
center of polishing pad), corresponding to the standard pattern, as
a foreign matter adhesion area in the surface of the polishing
member.
[0326] The image recognition includes pattern recognition, such as
the nearest neighbor method, Bayes decision rule, dynamic
programming matching (DP matching), Hidden Markov Model, etc. In
this embodiment, image analysis implies execution of at least one
of image transformation, feature extraction and image recognition.
Thereafter, the central processing unit 140, on receipt of a
command of the control program in the main memory 142, output the
foreign matter adhesion area to the output device 148, such as a
printer or a display.
[0327] The use of the adhesion region specifying apparatus of this
embodiment makes it possible to specify a foreign matter adhesion
position or a foreign matter adhesion area in a surface of a
polishing member, such as a polishing pad, when a scratch or
scratches are formed in a polished surface of a polishing object,
such as a semiconductor wafer, after carrying out polishing using a
polishing apparatus having no foreign matter region specifying
section.
[0328] Though in this embodiment standard patterns are produced in
the process for specifying a foreign matter adhesion area, it is of
course possible to pre-store prepared standard patterns in the
storage device 144 of the adhesion region specifying apparatus or
in an external storage medium, without producing the standard
patterns, and read the stored standard patterns from the storage
device or medium in the process for specifying a foreign matter
adhesion area. It is also possible to store the standard patterns,
produced in the process for specifying a foreign matter adhesion
area, not in the storage device 144 of the adhesion region
specifying apparatus, but in an external storage device, and read
the stored data from the external device in the specifying
process.
[0329] While the process for specifying a foreign matter adhesion
area using data on tracks of foreign matter has described, it is
possible to use, instead of the track data, data on a radial or
circumferential density distribution of scratch, data on the
presence or absence of a scratch at a specified position on a
polished surface, etc., analyzed from the track data, in specifying
a foreign matter adhesion area. In this case, image data, from
which a scratch is extracted, is analyzed to determine a radial or
circumferential density distribution of the scratch, the presence
or absence of the scratch at a specified position on the polished
surface, etc., and the determined data is used as a detection
pattern. Accordingly, data on a radial or circumferential density
distribution of a scratch, the presence or absence of a scratch at
a specified position on the polished surface, etc. is used as a
standard pattern.
[0330] The present invention makes it possible to prevent scratches
in a polished surface of a polishing object, which would be caused
by foreign matter adhering to a surface of a polishing member, thus
preventing the attendant lowering of the yield even when the
polishing object is large-sized. In particular, detection of
foreign matter adhering to a surface of a polishing member, makes
it possible to stop polishing and carry out cleaning of the surface
of the polishing member or replacement of the polishing member,
thereby preventing scratches on a polishing object and preventing
the lowering of the yield due to scratches. By specifying a foreign
matter adhesion position or a foreign matter adhesion area in a
surface of a polishing member, and intensively cleaning the foreign
matter adhesion position or the foreign matter adhesion area after
stopping polishing or during polishing, it becomes possible to
effectively remove foreign matter from the polishing member and
prevent scratches, caused by the foreign matter, on a polishing
object, thereby preventing the lowering of the yield. Furthermore,
the prevent invention makes it possible to effectively prevent
adhesion of foreign matter to a surface of a polishing member, thus
preventing scratches on a polishing object and preventing the
lowering of the yield due to scratches.
[0331] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
* * * * *