U.S. patent application number 11/466489 was filed with the patent office on 2007-03-01 for polishing pad, pad dressing evaluation method, and polishing apparatus.
This patent application is currently assigned to Tokyo Seimitsu Co., Ltd.. Invention is credited to Takashi Fujita.
Application Number | 20070049168 11/466489 |
Document ID | / |
Family ID | 37804914 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070049168 |
Kind Code |
A1 |
Fujita; Takashi |
March 1, 2007 |
POLISHING PAD, PAD DRESSING EVALUATION METHOD, AND POLISHING
APPARATUS
Abstract
The present invention provides: a polishing apparatus for
polishing a workpiece, comprising a polishing pad whose surface or
surface layer part is colored with a color different from a color
inside the polishing pad, a pad dresser which performs dressing of
the polishing pad, and an observing device which observes the
surface of the polishing pad; and a method for simply and
accurately monitoring the uniformity of dressing state of a
polishing pad in dressing the polishing pad of a polishing
apparatus such as a CMP device, in order to prolong the life of the
polishing pad, and to reduce the number of dummy wafers used in the
pad dressing.
Inventors: |
Fujita; Takashi;
(Mitaka-shi, JP) |
Correspondence
Address: |
ROBERTS, MLOTKOWSKI & HOBBES
P. O. BOX 10064
MCLEAN
VA
22102-8064
US
|
Assignee: |
Tokyo Seimitsu Co., Ltd.
Tokyo
JP
|
Family ID: |
37804914 |
Appl. No.: |
11/466489 |
Filed: |
August 23, 2006 |
Current U.S.
Class: |
451/6 |
Current CPC
Class: |
B24B 53/017 20130101;
B24B 49/12 20130101 |
Class at
Publication: |
451/006 |
International
Class: |
B24B 49/00 20060101
B24B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2005 |
JP |
2005-250124 |
Claims
1. A polishing pad of a polishing apparatus for polishing a
workpiece, comprising a surface or a surface layer part of the
polishing pad which is colored with a color different from a color
inside the polishing pad.
2. A pad dressing evaluation method for evaluating a dressing state
of pad dressing by which the surface of a polishing pad of a
polishing apparatus is dressed, comprising the steps of: performing
the pad dressing for a predetermined time period by using the
polishing pad whose surface is colored, or whose surface or surface
layer part is colored beforehand with a color different from a
color inside the polishing pad; and evaluating the dressing state
of the pad dressing on the basis of color irregularity of the
polishing pad surface ground by the pad dressing.
3. The pad dressing evaluation method according to claim 2, wherein
the color irregularity of the polishing pad surface is obtained by
measuring and quantifying color of the polishing pad surface ground
by the pad dressing at plural points.
4. The pad dressing evaluation method according to claim 2, wherein
the evaluation of the dressing state is to evaluate dressing
uniformity in the surface of the polishing pad.
5. The pad dressing evaluation method according to claim 3, wherein
the evaluation of the dressing state is to evaluate dressing
uniformity in the surface of the polishing pad.
6. A polishing apparatus for polishing a workpiece, comprising: a
polishing pad whose surface or surface layer part is colored with a
color different from a color inside the polishing pad; a pad
dresser which performs dressing of the polishing pad; and an
observing device which observes the surface of the polishing
pad.
7. A polishing apparatus for polishing a workpiece, comprising: a
polishing pad whose surface or surface layer part is colored with a
color different from a color inside the polishing pad; a pad
dresser which performs dressing of the polishing pad; and a
measuring device which measures and quantifies a color of the
polishing pad surface.
8. The polishing apparatus according to claim 7, further comprising
a judging device which judges whether or not the quantified values
are within a range set beforehand, and thereby judges whether or
not polishing of the workpiece is performed.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing pad, a pad
dressing evaluation method, and a polishing apparatus, and more
particularly to a polishing pad used in a polishing apparatus for
polishing a workpiece such as a semiconductor wafer, a pad dressing
valuation method for evaluating a dressing state of the polishing
pad, and the polishing apparatus.
[0003] 2. Description of the Related Art
[0004] As the microminiaturization and multilayering of a
semiconductor device progress, the CMP (Chemical Mechanical
Polishing) technique has become a technique indispensable to the
process of manufacturing a semiconductor device. The CMP technique
is used not only for flattening an interlayer insulating film but
also for various processes such as Cu wiring and element
isolation.
[0005] One of important specifications of the CMP for flattening is
the work in-plane uniformity of the polishing rate (polishing
uniformity). In order to improve the polishing uniformity, it is
important to uniformly distribute factors influencing the polishing
rate in the work surface.
[0006] The important factors include a polishing pressure, a
relative polishing speed, and the like, but the important factor
which has not been conventionally well quantified is a surface
state of a polishing pad (hereinafter, which may simply referred to
as pad). A preferable surface state of a polishing pad is formed by
pad dressing (hereinafter, which may simply be referred to as
dressing). In this respect, it is apparent also from the fact that
the polishing rate is reduced suddenly when the pad dressing is
stopped in the so-called in-situ dressing in which the pad dressing
can be performed simultaneously during polishing, that the strict
control of the surface state of the polishing pad is important.
[0007] The pad dressing means a process in which a pad dresser
(hereinafter, which may simply be referred to as dresser), to which
a grinding wheel such as diamond is attached, is brought into
contact with a polishing pad such as to shave off or roughen the
surface of the polishing pad, with the result that slurry holding
characteristics are made excellent so as to initialize the
polishing pad to a state where it is capable of polishing, and that
the polishing pad in use is made to recover the slurry holding
characteristics to maintain its polishing capability.
[0008] There is known a technique in which in performing pad
dressing, the surface shape of the pad is measured by scanning the
pad surface by a laser displacement sensor, and in which the
dressing time period of worn area and the dressing time period of
little worn area are changed so as to achieve the in-plane
uniformization in the pad dressing (for example, Japanese Patent
Application Laid-Open No. 2001-129754).
SUMMARY OF THE INVENTION
[0009] However, the technique described in Japanese Patent
Application Laid-Open No. 2001-129754 is a technique which takes a
long time to measure the entire surface of a polishing pad and is
too unrealistic to be applied during polishing. Further, the
technique is to control the manner of dressing by measuring the
surface shape of the pad before the pad dressing is performed.
Thus, the technique is not to evaluate whether or not the dressing
is uniformly performed after the pad dressing is performed, and
hence, cannot make it possible to grasp the dressing state of the
entire surface of the polishing pad.
[0010] Further, a polishing pad used in a CMP device has thickness
irregularity in itself, and irregularity due to attachment to the
polishing surface plate, as a result of which the polishing pad
surface after the attachment is not flat. The polishing pad surface
after the attachment usually has a height difference of about 30
.mu.m to 50 .mu.m.
[0011] However, in the CMP, in order to uniformly polish the wafer
surface, even the polishing pad surface having such waviness is
required to be uniformly dressed along the polishing pad
surface.
[0012] FIG. 4 shows a concept of the specification of pad dressing
required for the CMP. As shown in FIG. 4, in the case of dressing a
polishing pad 20 in which waviness with a height difference of
about 50 .mu.m is formed with a width of about 100 mm, it is
required to uniformly perform dressing along the waviness. Thus,
since the polishing pad is made of an elastic material, the pad
dressing in the CMP device can be regarded as the reference surface
grinding processing of the elastic material.
[0013] The state of dressing performed along such waviness of the
pad surface cannot be judged even by measuring the shape and size
of the pad surface.
[0014] Further, in the distribution state of pad dressing, the
distribution in the circumferential direction is very important
besides the distribution in the radial direction. This is because a
dresser is required to be brought into continuous contact with the
surface of the polishing pad rotated at high speed with a constant
pressure, without being intermittently brought into contact with
the surface of the polishing pad.
[0015] Specifically, in the case where a plate type pad dresser is
connected to a pressing device by using a flexible joint as shown
in a principle figure of FIG. 5, and used to follow the waviness of
the pad surface, a large frictional force is applied to the pad
dresser surface in contact with the polishing pad 20 rotated at a
high speed, thereby making the pad dresser inclined with respect to
the polishing pad 20.
[0016] When the pad dresser is inclined to reduce the frictional
force, it occurs that the pad dresser is made to return to the
original attitude. This occurs in a short time, as a result of
which the pad dresser is intermittently brought into contact with
the polishing pad 20 (stick slips). When the pad dresser is
inclined with respect to the polishing pad 20, the dressing is only
partially performed. Thus, it is apparent in principle that the
dressing is varied in the circumferential direction of the
polishing pad 20.
[0017] When the dressing is varied in the pad surface, the dressing
is continued until the entire pad surface is dressed by a fixed
amount, which results in a long dressing time. During this time
period, the dressing is made to partially progress, so that the
polishing rate (polishing amount per unit time) is gradually
increased. When the entire pad surface is dressed by a
predetermined amount, the polishing rate is finally stabilized.
[0018] While the polishing rate is gradually raised, it is
difficult to subject a product wafer to the polishing processing.
The product wafer can be subjected to the polishing processing only
after the polishing rate is stabilized. As a result, many dummy
wafers need to be used in order to stabilize the polishing
rate.
[0019] Further, when the pad dressing pressure is reduced, the
difference between the dressed and non-dressed parts in the pad
surface becomes remarkable. For this reason, it is necessary to
secure a minimum dressing amount even in the parts with small
dressing amount. Therefore, it is necessary to set the dressing
pressure a little higher so as to enable any part of the pad to be
dressed by the minimum dressing amount.
[0020] To this end, the average pad amount removed by the pad
dressing is set larger to some extent. As a result, the consumption
amount of the pad surface is increased, leading to a problem that
the life of the polishing pad is short.
[0021] Such a problem has not become known because there is no
effective method to immediately measure the dressing distribution
(grinding distribution) in the pad surface. As a result, many dummy
wafers are used for setting up the polishing pad, with the result
that the pad life after the setting-up is short.
[0022] The present invention has been made in view of the above
described circumstances. An object of the present invention is to
provide a method for simply and accurately monitoring the
uniformity of dressing state of a polishing pad in dressing the
polishing pad of a polishing apparatus such as a CMP device, and to
provide a polishing pad and a polishing apparatus for use in the
method.
[0023] In order to achieve the above described object, according to
a first aspect of the present invention, there is provided a
polishing pad of a polishing apparatus for polishing a workpiece,
the polishing pad characterized in that the surface or the surface
layer part of the polishing pad is colored with a color different
from a color inside the polishing pad.
[0024] According to the first aspect of the invention, the surface
or the surface layer part of the polishing pad is colored with a
color different from a color inside the polishing pad. Thus, when
the polishing pad is dressed, in the dressed part, the colored
parts are removed to enable the base of the polishing pad to be
seen, while in the non-dressed part, the colored part is left as it
is. This makes it possible to easily grasp the polishing
irregularity in the pad dressing on the basis of the distribution
state of the color of the polishing pad surface, and to thereby
make the uniformity of the dressing easily judged.
[0025] According to a second aspect of the present invention, there
is provided a pad dressing evaluation method for evaluating a
dressing state of pad dressing by which the surface of a polishing
pad of a polishing apparatus is dressed, the pad dressing
evaluation method characterized in that the polishing pad whose
surface is colored or whose surface or surface layer part is
colored beforehand with a color different from a color inside the
polishing pad is used, the pad dressing is performed for a
predetermined time period, and the dressing state of the pad
dressing is evaluated on the basis of color irregularity of the
polishing pad surface ground by the pad dressing.
[0026] Further, according to a third aspect of the present
invention, in the second aspect, the color of the polishing pad
surface ground by the pad dressing is preferably measured and
quantified at plural points, thereby enabling the color
irregularity of the polishing pad to be obtained.
[0027] Further, according to a fourth aspect of the present
invention, in one of the second and third aspects, the evaluation
of the dressing state can be performed by evaluating dressing
uniformity in the surface of the polishing pad.
[0028] According to the pad dressing valuation method of the
present invention, it is possible to qualitatively and
quantitatively grasp the in-plane uniformity of the pad dressing.
This makes it possible to prevent excessive grinding by the pad
dressing, so that the life of the polishing pad can be
prolonged.
[0029] According to a fifth aspect of the present invention, there
is provided a polishing apparatus for polishing a workpiece,
characterized by comprising: a polishing pad whose surface or
surface layer part is colored with a color different from a color
inside the polishing pad; a pad dresser which performs dressing of
the polishing pad; and an observing device which observes the
surface of the polishing pad.
[0030] Further, according to a sixth aspect of the present
invention, there is provided a polishing apparatus for polishing a
workpiece, characterized by comprising: a polishing pad whose
surface or surface layer part is colored with a color different
from a color inside the polishing pad; a pad dresser which performs
dressing of the polishing pad; and a measuring device which
measures and quantifies color of the polishing pad surface. In the
sixth aspect according to the present invention, it is possible to
provide a judging device which judges whether or not the quantified
values are within a range set beforehand, and thereby judges
whether or not polishing of the workpiece is performed.
[0031] According to the polishing apparatus of the present
invention, it is possible to easily check the dressing state of the
polishing pad. Further, the surface state of the polishing pad can
be numerically represented. Thereby, after the pad dressing is
performed, whether or not the polishing of a workpiece is to be
performed can be judged by determining whether or not the surface
state of the pad is normal. As a result, the number of dummy wafers
used in the pad dressing can be substantially reduced.
[0032] As described above, according to the polishing pad and the
pad dressing evaluation method of the present invention, it is
possible to easily grasp the grinding irregularity in the pad
dressing, and to thereby easily judge the uniformity of the
dressing. Further, according to the polishing apparatus of the
present invention, excessive grinding in the pad dressing can be
prevented, thereby making it possible to prolong the life of the
polishing pad, and to reduce the number of dummy wafers used in the
pad dressing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a figure showing a constitution of a polishing
apparatus according to an embodiment of the present invention;
[0034] FIG. 2 is a flow chart showing a pad dressing valuation
method according to the present invention;
[0035] FIG. 3 is an illustration showing results of an example;
[0036] FIG. 4 is an illustration showing a concept of pad dressing
required for the CMP;
[0037] FIG. 5 is a conceptual diagram showing a constitution of a
conventional pad dresser;
[0038] FIG. 6 is a table representing conditions in the
examples;
[0039] FIG. 7 shows a table showing dresser oscillation conditions
in the examples;
[0040] FIG. 8 is a figure showing measuring points in the polishing
pad in the examples;
[0041] FIG. 9 is a table showing XY coordinates of the measuring
points in the polishing pad in the examples;
[0042] FIG. 10 is a figure showing the definition of color
digitization in the examples;
[0043] FIG. 11 is a table showing measurement data in the
examples;
[0044] FIG. 12 is a bird's eye view 1 showing a measurement result
in the example; and
[0045] FIG. 13 is a bird's eye view 2 showing a measurement result
in the example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] In the following, preferred embodiments of a polishing pad,
a pad dressing evaluation method, and a polishing apparatus
according to the present invention will be described in detail with
reference to the accompanying drawings. Note that in each figure,
the same member is designated by the same reference numeral or the
same reference character.
[0047] FIG. 1 shows a constitution of a polishing apparatus
according to an embodiment of the present invention. A polishing
apparatus 10 shown in FIG. 1 is constituted mainly by a polishing
surface plate 11, a polishing pad 20, a wafer carrier (not shown),
a pad dresser 30, a camera 41 and a monitor television 42 which
constitute an observing device for observing the surface of the
polishing pad 20, a measuring device 51 which measures and
quantifies color of the polishing pad 20 surface, and a controller
60 which controls the operation of each section of the polishing
apparatus 10.
[0048] The polishing surface plate 11 is rotated in the direction
of the arrow E in FIG. 1 by driving a motor (not shown) connected
with a rotating shaft 11a. A wafer carrier for holding a wafer as a
workpiece is driven so as to be rotated by the motor (not shown).
Further, the polishing pad 20 is attached to the upper surface of
the polishing surface plate 11, and a slurry is supplied to the
surface of the polishing pad 20 from a slurry supply nozzle (not
shown).
[0049] The polishing pad 20 is a thin disc-like plate formed by an
elastic base material made of foamed polyurethane. On the upper
surface of the polishing pad, many shallow grooves are formed in a
grid shape in order to improve slurry holding characteristics.
Further, the surface or the surface layer part of the upper surface
of the polishing pad 20 is colored with a color different from a
color inside the polishing pad 20.
[0050] The polishing pad may be colored by being mixed with and
laminating a pigment different from a pigment inside the polishing
pad only on the surface layer part, or by forming, on the surface
of the polishing pad, a film with a color different from a color
inside the polishing pad. There are various paints and dyes for
coloring the surface of the polishing pad, which include, for
example, Pyrokeep TS made by Otsuka Chemical Co., Ltd., Urban Cera
made by Nissin Kasei Co., Ltd., Silvia SP Yogore Guard made by
Nihon Tokushu Toryo Co., Ltd., Regi Guard FA Renew and High Clean
made by Daido Co., Ltd., Bell Clean made by NOF Co., Ltd., Amix
Cone made by Atomix Co., Ltd., Aqua Top F-2 made by Sumitomo Seika
Chemicals Co. Ltd., Magic Ink made by Teranishi Chemical Industry
Co., Ltd., and the like.
[0051] Besides these materials, various kinds of color materials
can be used, if they attach only to the very thin surface layer of
the polishing pad 20 without penetrating deeply into the polishing
pad 20.
[0052] The pad dresser 30 is rotated in the direction of the arrow
F in FIG. 1 and pressed against the surface of the rotating
polishing pad 20 to grind and roughen the surface of the polishing
pad 20. Thereby, the polishing pad 20 is made to have excellent
slurry holding characteristics so as to be initialized to a state
where it can be polished, and the polishing pad 20 in use is made
to recover the slurry holding characteristics so as to maintain the
polishing capability.
[0053] The camera 41 constituting the observing device which
observes the surface of the polishing pad 20, is arranged above the
polishing pad 20, and a captured image is displayed on the monitor
television 42 which is separately arranged. Further, the measuring
device 51 which measures and quantifies color of the surface of the
polishing pad 20 is connected to the camera 41.
[0054] The camera 41 and the measuring device 51 are provided so as
to be traversable in the direction of the arrow G in FIG. 1, so
that they are capable of observing from the central part of the
polishing pad 20 to the periphery thereof by a driving device (not
shown). This makes it possible to observe the entire surface of the
polishing pad 20 in combination with the rotation of the polishing
pad 20.
[0055] A color is defined by three elements of hue (corresponding
to a wavelength of monochromatic light), saturation (brightness,
i.e., a degree of not being whitened), and lightness (luminosity,
i.e., the intensity of light). As the measuring device 51 according
to the present invention, a spectral color difference meter which
measures hue, or a color and color difference meter which measures
saturation, and the like is preferably used.
[0056] As the spectral color difference meter, there is a product
number NF 333 made by Nihon Densyoku Kogyo Co. Ltd., and the like.
As the color and color-difference meter, there are product numbers
CR-400, CR-410 made by Konica Minolta Co., Ltd., and the like.
[0057] A judging device 61 constituted by a computer incorporated
in the controller 60 which controls operations of each section of
the polishing apparatus 10, judges the dressing state of the pad
from a color value of the surface of the polishing pad 20 which is
quantified by the measuring device 51.
[0058] Note that the polishing apparatus 10 is provided with both
the camera 41 and the measuring device 51 which are the observing
device, but the polishing apparatus 10 may be provided only with
the camera 41 so as to perform visual observation, or may be
provided only with the measuring device 51 to quantify the pad
surface state.
[0059] Next, a pad dressing evaluation method according to the
present invention is explained using a flow chart shown in FIG. 2.
First, while the polishing pad 20 whose surface or surface layer
part is colored with a color different from a color inside the
polishing pad 20 is rotated, water is supplied to the surface of
the polishing pad 20, and the pad dressing is performed by the
rotating pad dresser 30 for a predetermined time period (step
S1).
[0060] Next, the surface of the polishing pad 20 subjected to the
pad dressing is imaged by the camera 41, so that the dressing state
of the polishing pad 20, particularly, the dressing uniformity in
the pad surface is evaluated from color irregularity of the pad
surface using the monitor television 42. At this time, the image
may be compared with a sample image obtained beforehand, so as to
judge whether the dressing state is acceptable or not (step
S2).
[0061] Further, instead of the camera, the surface of the polishing
pad 20 is directly measured by a color difference meter as the
measuring device 51, so as to enable the dressing state to be
digitized. Further, the image obtained by the camera 41 may be
digitized by the color difference meter. In this case, the
digitization is preferably performed by measuring plural points of
the polishing pad 20.
[0062] In digitizing the image, the RGB values and the Munsell
values which are used for digitizing a general color, may be
utilized to perform the digitization. Further, the color change may
be set in plural stages, so as to make a numerical value assigned
to each of the stages, as a result of which the color change is
quantified by an original evaluation method.
[0063] In this way, a standard deviation of the numerical values in
the pad surface is obtained by performing digitization for
respective points in the polishing pad 20. The uniformity of the
dressing state in the pad surface is obtained by dividing the
obtained standard deviation by the average value of the numerical
values (step S3).
[0064] Next, whether or not the obtained dressing uniformity in the
polishing pad 20 surface is within a range set beforehand is judged
by the judging device 61 in the controller 60 (step S4). When the
in-plane uniformity of the dressing is within the range set
beforehand, the process is moved to the polishing process of a
product wafer (step S5).
[0065] When the in-plane uniformity of the dressing is deviated
from the range set beforehand in step S4, whether or not the pad
dressing is further continued is judged by the judging device 61 on
the basis of the degree of deviation from the set range (step
86).
[0066] When it is judged that the re-dressing is to be performed in
step S6, the process is returned to step S1. When it is judged that
the dressing is not to be continued, an alarm is outputted, and the
polishing apparatus 10 is temporarily stopped (step S7).
[0067] Note that in the flow chart shown in FIG. 2, the flow is
described such that step S3 is performed after step S2, but the
order of step S2 and step S3 may be reversed, or the dressing state
may be evaluated only by one of step S2 and step S3.
EXAMPLE 1
[0068] First, the surface of the polishing pad 20 made of foamed
polyurethane is colored by uniformly spraying an oil-based color
spray on the surface of the polishing pad 20. The thickness of
colored layer is set to about 5 .mu.m. The polishing pad 20 is
attached to the polishing surface plate 11 and rotated. In this
state, the pad dressing is performed using two kinds of pad
dressers (referred to as A dresser and B dresser) for the same time
period, respectively. Then, the dressing state (the dressing
uniformity in the pad surface) is compared on the basis of color
irregularity of the pad surface.
[0069] The pad dressing conditions are set such that the rotation
speed of the polishing pad 20 is 30 rpm and the rotation speed of
the pad dresser is 80 rpm. Under these conditions, the pad dressing
is performed while supplying pure water to the surface of the
polishing pad 20.
[0070] FIG. 3 shows a result of the pad dressing. As is apparent
from FIG. 3, it can be seen that color irregularity is observed in
the pad surface as the result of the pad dressing performed by
using the dresser A, and that the dressing is inferior in the
in-plane uniformity.
[0071] On the other hand, it can be seen that almost no color
irregularity is observed in the pad surface as the result of the
pad dressing performed by using the dresser B, and that the
dressing is excellent in the in-plane uniformity. In this case, the
surface roughness of the polishing pad 20 is Ra 0.5 .mu.m, and the
surface is roughened uniformly.
EXAMPLE 2
[0072] In the example 1, a polishing pad with a relatively small
diameter is dressed, and the dressing effect is simply verified by
observing the color irregularity. In the present example 2, a
polishing pad with a large diameter, which is actually used in the
polishing apparatus 10, is dressed, and the uniformity of the pad
dressing is quantified.
[0073] In the present example 2, the uniformity of the pad dressing
is quantified in the following two cases: a case (referred to as
case 1) where the dressing is performed by using a conventional
type pad dresser (referred to as 4-inch disk type dresser) produced
by making diamond abrasive grains electrodeposited on a disk with a
diameter of 100 mm; and a case (referred to as case 2) where the
dressing is performed by using a new type pad dresser (referred to
as 4-inch elastic brush type dresser) produced by making a number
of piano wires (linear elastic bodies) planted in a brush shape on
a disk with a diameter of 100 mm, on the tip of which piano wires
diamond abrasive grains are electrodeposited. The details are
explained below.
[0074] First, the surface of the polishing pad 20 with a diameter
of 760 mm made of foamed polyurethane (IC1400 made by Nitta Haas
Incorporated) is colored with Magic Ink (black) made by Teranishi
Chemical Industry Co., Ltd. The thickness of the colored layer is
set to about 5 .mu.m.
[0075] The pad dressing conditions are set such that the rotation
speed of the polishing pad 20 is 30 rpm and the rotation speed of
the pad dresser is 80 rpm. Under these conditions, the pad dressing
is performed, while the pad is made to oscillate in the radial
direction, and pure water is supplied to the surface of the
polishing pad 20. The dressing pressure is set to 4 Kgf, and the
dressing time periods are set to 15 minutes in the case 1 and 21
minutes in the case 2, respectively.
[0076] The dressing conditions are summarized in FIG. 6 and FIG. 7.
When the pad dresser is made to oscillate in the radial direction
of the pad, the area is increased in accordance with the increase
of the radius. Thus, the oscillation speed is reduced by the amount
corresponding to the increase in the area, thereby making the
staying period of the pad dresser on the pad increased.
Specifically, as shown in the table of FIG. 7, the polishing pad 20
is divided into eleven stages, of which the first to tenth stages
are set by dividing the polishing pad 20 from the central position
with the radius of 75 mm to the periphery in increments of 30 mm,
and the eleventh stage is set by the last fraction of 5 mm. In this
state, the staying period in the respective stages is changed.
[0077] In each of the case 1 and the case 2, the color of the pad
surface is measured and quantified at 81 points in the surface of
the polishing pad 20 after dressing. The measuring points in the
surface of the polishing pad 20 are shown in FIG. 8, and coordinate
values of each measuring point are shown in a table of FIG. 9.
[0078] The apparatus used for measuring the color is the color and
color difference meter CR-400 made by Konica Minolta Co., Ltd., and
the color is digitized on the basis of the definition in which
numerical values from 0 to 20 are assigned as shown in FIG. 10.
That is, the part which is not colored is assigned to 20 (upper
limit), the part which is completely colored is assigned to 0
(lower limit), and continuous numerical values are assigned between
the upper and lower limits.
[0079] FIG. 11 is a table which shows XY coordinates of respective
measuring points, and the measured values corresponding to the
respective measuring points in the case 1 and the case 2. FIG. 12
is a bird's-eye view showing the result of the case 1, in which the
average value of the respective measuring points is 10.46, and the
standard deviation in terms of 1.sigma. value is 2.379. When the
dressing uniformity is defined as "a value obtained by dividing the
standard deviation of all measuring points by the average value
thereof", the dressing uniformity is 22.73%.
[0080] FIG. 13 is also a bird's-eye view showing the result of the
case 2, in which the average value of the respective measuring
points is 10.93, and the standard deviation in terms of 1.sigma.
value is 0.65. When the dressing uniformity is defined as "a value
obtained by dividing the standard deviation of all measuring points
by the average value thereof", the dressing uniformity is
6.03%.
[0081] As is apparent from the bird's-eye views shown in FIG. 12
and FIG. 13, a large amount of color irregularity is observed in
the case 1, and little amount of color irregularity is observed in
the case 2. Further, since the dressing uniformity is defined as
described above, the smaller numerical value indicates the more
excellent dressing uniformity. In this way, the dressing uniformity
can be easily digitized, and thereby, it is possible to perform
qualitative and quantitative comparison between the case 1 and the
case 2.
[0082] As describe above, according to a polishing pad, a pad
dressing evaluation method, and a polishing apparatus of the
present invention, the in-plane uniformity of a dressing state of
the polishing pad can be simply and accurately evaluated. This
makes it possible to prevent excessive grinding in the pad dressing
and to thereby make the life of the polishing pad prolonged. In
addition, this also makes it possible to effectively perform the
pad dressing and to thereby reduce the number of dummy wafers.
* * * * *