U.S. patent application number 11/806581 was filed with the patent office on 2007-10-11 for substrate polishing apparatus and substrate polishing method.
Invention is credited to Makoto Akagi, Norio Kimura, Tatsuya Kohama.
Application Number | 20070238395 11/806581 |
Document ID | / |
Family ID | 26592731 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070238395 |
Kind Code |
A1 |
Kimura; Norio ; et
al. |
October 11, 2007 |
Substrate polishing apparatus and substrate polishing method
Abstract
A substrate polishing apparatus wherein a semiconductor
substrate is held by a top ring 10-2 or 11-2 and is pressed against
a polishing surface of a polishing table 10-1 or 10-2. A surface to
be polished of the semiconductor substrate is polished by a
relative movement between the semiconductor substrate and the
polishing surface. The apparatus includes a pressing force changing
mechanism for changing a pressing force for pressing the
semiconductor substrate, a relative movement seed changing
mechanism for changing the number of revolutions of the top ring
and/or the polishing table, and a control mechanism. The control
mechanism performs the polishing through plural polishing processes
on the polishing table 10-1 or 10-2 while changing the pressing
force and the number of revolutions.
Inventors: |
Kimura; Norio; (Kanagawa,
JP) ; Kohama; Tatsuya; (Kanagawa, JP) ; Akagi;
Makoto; (Kanagawa, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
26592731 |
Appl. No.: |
11/806581 |
Filed: |
June 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09864208 |
May 25, 2001 |
|
|
|
11806581 |
Jun 1, 2007 |
|
|
|
Current U.S.
Class: |
451/6 ;
156/345.12; 257/E21.304; 257/E21.583 |
Current CPC
Class: |
H01L 21/3212 20130101;
B24B 37/042 20130101; H01L 21/0209 20130101; B24B 49/16 20130101;
H01L 21/7684 20130101; H01L 21/67046 20130101; B24B 49/006
20130101; H01L 21/02074 20130101; H01L 21/67051 20130101 |
Class at
Publication: |
451/006 ;
156/345.12 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24B 7/00 20060101 B24B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2000 |
JP |
157007/2000 |
Oct 11, 2000 |
JP |
310454/2000 |
Claims
1. A substrate polishing apparatus comprising: a polishing table
having a polishing surface; and a top ring for holding a substrate;
wherein a semiconductor substrate held by said top ring is pressed
against said polishing surface of said polishing table and a
surface to be polished of the semiconductor substrate is polished
by a relative movement between the semiconductor substrate and said
polishing surface, and said semiconductor substrate has a copper
plating film layer formed on a barrier layer; the apparatus further
comprising: pressing force changing mechanism for changing a
pressing force for pressing the semiconductor substrate; revolution
number changing mechanism for changing the revolution number of the
top ring and/or the polishing table; and control means; wherein
said control means performs plural polishing processes on the same
polishing table while changing the pressing force and the
revolution number through said pressing force changing mechanism
and said revolution number changing mechanism, the apparatus
further comprising: an eddy current sensor and an optical sensor
within said polishing table, wherein the eddy current sensor
measures a film thickness of the copper plating film layer until
the film thickness of the copper plating film layer reaches a
predetermined film thickness which is measurable by the optical
sensor, and the optical sensor measures the film thickness of the
copper plating film layer when the film thickness of the copper
plating film layer reaches the predetermined film thickness or less
than it.
2. The substrate polishing apparatus according to claim 1, further
comprising dressing means for dressing said polishing surface of
said polishing table or cleaning means for cleaning said polishing
surface of said polishing table, and wherein said control means
controls said dressing means or said cleaning means between the
plural polishing processes to effect dressing or cleaning of said
polishing surface of said polishing table.
3. A substrate polishing method in which a semiconductor substrate
held by a top ring is pressed against a polishing surface of a
polishing table and a surface to be polished of the semiconductor
substrate is polished by a relative movement between the
semiconductor substrate and said polishing surface, wherein: said
semiconductor substrate has a copper plating film layer formed on a
barrier layer, the semiconductor substrate is polished on the same
polishing table through plural polishing processes while changing a
pressing force for pressing the semiconductor substrate and the
number of revolutions of said top ring and/or said polishing table,
during the plural polishing processes, the eddy current sensor
measures the film thickness of the copper plating film layer until
the film thickness of the copper plating film layer reaches a
predetermined film thickness which is measurable by the optical
sensor, and the optical sensor measures the film thickness of the
copper plating film layer when the film thickness of the copper
plating film layer reaches the predetermined film thickness or less
than it.
4. The substrate polishing method according to claim 3, wherein,
when said plural polishing processes are performed, the polishing
is effected while adding polishing liquid and/or reagent liquid
having pH at the same side as pH 7.
5. The substrate polishing method according to claim 3, wherein,
when said plural polishing processes are performed, the polishing
is effected by using same abrasive grain.
6. The substrate polishing method according to claim 3, wherein the
polishing surface of the polishing table is cleaned between the
plural stage polishing processes, and after the polishing surface
is cleaned, the next stage polishing process is performed.
Description
[0001] This is a divisional application of U.S. patent application
Ser. No. 09/864,208, filed May 25, 2001, now abandoned.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a substrate polishing
apparatus and a substrate polishing method for polishing a metallic
coating or film formed on a surface of a substrate used in a
semiconductor device manufacturing process and particularly in a
process for forming metallic wiring with copper and the like.
Further, the present invention relates to a substrate polishing
method for flattening and mirror-polishing a film formed on a
surface of a semiconductor substrate, and more particularly it
relates to a substrate polishing method suitable for flattening and
mirror-polishing a metallic film formed on the surface of the
substrate.
[0003] As the integration density on a semiconductor device has
been increased, adoption of a material of higher conductivity has
been requested as a material for forming a wiring circuit. To
satisfy such request, a polishing method has been brought to notice
in which a film having high conductivity and made of copper or an
alloy thereof is formed on a surface of a substrate having grooves
and/or holes corresponding to a wiring pattern. The substrate
surface is polished by a polishing apparatus with chemical and
mechanical polishing (CMP) in such a manner that the film is
removed from the substrate surface while remaining film material
fills the grooves and/or holes corresponding to the wiring
pattern.
[0004] As shown in FIG. 1(a), in a semiconductor substrate W, an
insulation film 102 made of SiO.sub.2 is deposited on a conductive
layer 101a formed on a semiconductor substrate 101 on which a
semiconductor elements are formed, and contact holes 103 and wiring
grooves 104 are formed in the film by a lithography etching
technique. A barrier layer 105 made of TiN is coated on the film
and a feed seed layer 107 for electro-plating is formed on the
barrier layer.
[0005] Then, as shown in FIG. 1(b), by applying copper (Cu) plating
on the surface of the semiconductor substrate W, the contact holes
103 and the grooves 104 of the semiconductor substrate 101 are
filled with copper, and a copper plating layer 106 is deposited on
the insulation film 102. Thereafter, by chemical and mechanical
polishing, the copper plating layer 106 on the insulation film 102
is removed so that the surface of the copper plating layer 106
filled in the contact holes 103 and the wiring grooves 104 become
substantially flush with the surface of the insulation film 102. As
a result, the wiring comprised of the copper plating layer 106 as
shown in FIG. 1(c) is obtained.
[0006] When the barrier layer 105, feed seed layer 107 and copper
plating layer 106, as plural kinds of layers formed on the
insulation film 102, are polished by the chemical and mechanical
polishing, the polishing must be performed while changing polishing
conditions at two or three stages. And, in each stage of polishing,
since a polishing table must be changed, as a whole, the number of
tables is increased and the entire polishing apparatus is made
bulky and complicated and is also made more expensive. Further, the
through-put of the semiconductor substrate polishing cannot be
improved.
[0007] Further, in recent years, as the integration density on a
semiconductor device has been increased, circuit wiring has been
made finer and the distance between the wirings has been shortened.
Particularly, in the case of optical lithography handling a line
width of 0.5 .mu.m or less, since the focal depth becomes small,
the flatness of a focusing plane of a stepper must be enhanced. To
this end, a surface of a semiconductor wafer must be flattened. As
one of such flattening methods, polishing by means of a polishing
apparatus is adopted.
[0008] In the past, such a polishing apparatus includes a turn
table on which a polishing cloth is adhered, or a turn table
constituted by a grinding stone having an upper polishing surface,
and a top ring, which turn table and top ring are rotated
independently with an independent number of revolutions. The top
ring applies a predetermined pressure onto the turn table, thereby
flattening and mirror-polishing a surface of an object to be
polished (polished object) interposed between the turn table and
the top ring.
[0009] FIG. 1(d) is a cross-sectional view of a substrate as an
object to be polished. As shown, in the substrate, grooves or holes
are formed in an upper surface of an oxidation film 301 such as a
SiO.sub.2 film formed on an upper surface of a silicon substrate
(not shown). A titanium (Ti) film 302 and a titanium nitride (TiN)
film 303 are successively formed on the surface (including inner
surfaces of the grooves or holes) of the oxidation film 301. A
tungsten (W) film 304 is formed on the TiN film to fill the grooves
or holes.
[0010] In the past, in order to polish the substrate having the
above-mentioned cross-section, the substrate was polished by a
single polishing process without changing a substrate pressing load
pressing the substrate against the polishing surface of the
polishing table, the number of revolutions of the polishing table
and the top ring, and a slurry. For example, after slurry polishing
was effected by using slurry as a polishing liquid with a substrate
pressing load of 500 kgf/cm.sup.2, water polishing was effected
with a substrate pressing load of 50 kgf/cm.sup.2. If the formed
surface of the tungsten film 304 of the substrate is polished by
such polishing processes until the titanium (Ti) film 302 is
removed, as shown in FIG. 1(e), the oxidation film 301 will
subjected to erosion, i.e., oxide erosion, which leads in
unevenness polished surface, thereby preventing uniform or flat
polishing.
SUMMARY OF THE INVENTION
[0011] The present invention is made in consideration of the
above-mentioned conventional drawbacks. An object of the present
invention is to provide a substrate polishing apparatus and a
substrate polishing method in which, when plural kinds of films on
a semiconductor substrate are polished, plural stage polishing
processes can be performed on a single polishing table to reduce
the number of tables, to make the entire apparatus compact and to
enhance the through-put of semiconductor substrate polishing.
[0012] Another object of the present invention is a substrate
polishing method suitable for uniformly flattening and
mirror-polishing a surface to be polished by polishing films formed
on a substrate surface, particularly plural different metallic
films successively formed on the substrate surface.
[0013] To achieve the above objects, according to a first aspect of
the present invention, there is provided a substrate polishing
apparatus comprising a polishing table having a polishing surface
and a top ring for holding a substrate. The semiconductor substrate
held by the top ring is pressed against the polishing surface of
the polishing table and a surface to be polished of the
semiconductor substrate is polished by a relative movement between
the semiconductor substrate and the polishing surface. It further
comprises a pressing force changing mechanism for changing a
pressing force for pressing the semiconductor substrate, a relative
movement changing mechanism for changing the speed of relative
movement of the top ring and/or the polishing table, and a control
mechanism. The control mechanism performs plural polishing
processes on the same polishing table while changing the pressing
force and the number of revolutions through the pressing force
changing mechanism and the revolution number changing
mechanism.
[0014] According to another aspect of the present invention, in the
above-mentioned substrate polishing apparatus, there is further
provided a film thickness detecting means for detecting a film
thickness of the semiconductor substrate. The control mechanism
performs transfer from a preceding polishing process to a next
polishing process on the basis of a film thickness detection signal
detected by the film thickness detecting means.
[0015] According to a further aspect of the present invention, in
the above-mentioned substrate polishing apparatus, there is further
provided a dressing means for dressing the polishing surface of the
polishing table or a cleaning mechanism for cleaning the polishing
surface of the polishing table. The control mechanism controls the
dressing mechanism or the cleaning mechanism between the polishing
processes to effect dressing or cleaning of the polishing surface
of the polishing table.
[0016] According to a still further aspect of the present
invention, there is provided a substrate polishing method in which
a semiconductor substrate held by a top ring is urged against a
polishing surface of a polishing table and a surface to be polished
of the semiconductor substrate is polished by a relative movement
between the semiconductor substrate and the polishing surface. The
semiconductor substrate is polished on the same polishing table
through plural polishing processes while changing a pressing force
pressing the semiconductor substrate and the number of revolutions
of the top ring and/or the polishing table.
[0017] A purpose for polishing the semiconductor substrate on which
a pattern was formed is to remove minute unevenness (for example,
unevenness having a width of 0.1 .mu.m to 2 .mu.m and height of 500
nm to 1000 nm) and to achieve flatness. However, since a polishing
pad has elasticity, the pad follows a certain unevenness, with the
result that the unevenness cannot be removed completely. In this
case, the flatness is apt to be achieved if the polishing is
performed with a small load (urging force) and faster rotational
speed. However, since the load is small, the polishing speed is
reduced. In consideration of this, as mentioned above, by
performing the polishing on the same polishing table through the
plural polishing processes while changing the pressing force for
pressing the semiconductor substrate and the number of revolutions
of the top ring and/or the polishing table, the polishing is
firstly effected with a great load and fast rotational speed, and,
thereafter, the unevenness is removed with a small load. In this
way, polishing that flattens the surface to be polished can be
achieved. Further, by reducing the relative speed for finish
polishing, the removal of scratches on the surface can be
facilitated.
[0018] According to a further aspect of the present invention, in
the above-mentioned substrate polishing method, when the plural
polishing processes are performed, the polishing is effected while
adding polishing liquid and/or reagent liquid having pH at the same
side as pH 7.
[0019] According to a still further aspect of the present
invention, in the above-mentioned substrate polishing method, when
the plural polishing processes are performed, the polishing is
effected by using the same abrasive grain.
[0020] According to a further aspect of the present invention,
there is provided a substrate polishing method in which a
semiconductor substrate held by a top ring is urged against a
polishing surface of a polishing table and a surface to be polished
of the semiconductor substrate is polished by a relative movement
between the semiconductor substrate and the polishing surface. The
polishing is effected on the single polishing table through plural
stage polishing processes, and, after one stage polishing process
is finished, the polishing surface of the polishing table is
cleaned. Then the next stage polishing process is performed.
[0021] To achieve the above object, according to a further aspect
of the present invention, there is provided a substrate polishing
method in which a substrate held by a top ring is urged against a
polishing surface of a polishing table and a film formed on a
surface of the semiconductor substrate is polished to achieve
flatness by a relative movement between the semiconductor substrate
and the polishing surface. The polishing is performed through three
or more polishing processes in which at least one of a substrate
pressing load for pressing the substrate against the polishing
surface of the polishing table, a relative speed between the
polishing table and the substrate, and the polishing liquid is
changed.
[0022] As mentioned above, by performing the polishing through
three or more polishing processes in which at least one of the
substrate pressing load, the relative speed between the polishing
table and the substrate, and the polishing liquid is changed (for
example, the substrate pressing load is changed), the uniformity of
the polished surface is improved in comparison with the prior art,
which will be described later.
[0023] According to a still further aspect of the present
invention, in the above-mentioned substrate polishing method,
completion of at least a last polishing process among three or more
polishing processes is determined by the detection of a thickness
of the film.
[0024] As mentioned above, by determining the completion of the
polishing process on the basis of the detection of the thickness of
the film, for example, when the polishing of a certain kind of film
is finished and the transfer to the polishing for another kind of
film is effected, a polishing condition (for example, polishing
liquid and substrate pressing load) can be changed to suit such
kind of film.
[0025] According to a further aspect of the present invention, in
the above-mentioned substrate polishing method, after at least a
last polishing process among three or more polishing processes is
finished, a water polishing process using water as the polishing
liquid is performed.
[0026] According to a still further aspect of the present
invention, in the above-mentioned substrate polishing method, an
atomizer polishing process using a mixture of water and an inert
gas as the polishing liquid is added to the water polishing
process.
[0027] As mentioned above, by performing the water polishing
process and the atomizer polishing process after the last polishing
process is finished, since high temperature portions of the surface
to be polished of the substrate and the polishing surface of the
polishing table, heated during the preceding polishing process, are
cooled and the polishing liquid (for example, slurry) used in the
preceding polishing process is removed, erosion of the surface to
be polished of the substrate can be prevented, thereby enhancing
uniformity.
[0028] According to the other aspect of the present invention, in
the above-mentioned substrate polishing method, the films formed on
the substrate surface may be an oxidation film, a Ti film, a TiN
film and a W film successively laminated on the substrate
surface.
[0029] As mentioned above, by polishing the substrate on which the
W film was formed through three or more polishing processes while
changing the substrate pressing load, for example, uniformity of
the surface to be polished of the substrate will be improved in
comparison with the prior art, as will be described later.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIGS. 1(a) to 1(c) are explanatory views for forming a
circuit wiring on a semiconductor substrate, FIG. 1(d) is a
sectional view of a substrate to be polished, and FIG. 1(e) is a
sectional view of a substrate polished by a conventional substrate
polishing method;
[0031] FIG. 2 is a plan view showing a substrate processing
apparatus having a substrate polishing apparatus according to the
present invention;
[0032] FIG. 3 is a view showing a construction of a polishing
device of the substrate polishing apparatus according to the
present invention;
[0033] FIG. 4 is a view showing a construction of a cleaning
mechanism for a polishing surface of a polishing table of the
substrate polishing apparatus according to the present
invention;
[0034] FIG. 5 is a view showing a construction of a cleaning
mechanism for a polishing surface of a polishing table of the
substrate polishing apparatus according to the present
invention;
[0035] FIG. 6 is a view showing a construction of a first cleaning
machine of the substrate polishing apparatus according to the
present invention;
[0036] FIG. 7 is a perspective view of a second robot of the
substrate polishing apparatus according to the present
invention;
[0037] FIG. 8 is a view showing a construction of a film thickness
measuring device for measuring a film thickness of the substrate
during polishing used by the substrate polishing apparatus
according to the present invention; and
[0038] FIG. 9 is a schematic view showing a substrate polishing
apparatus carrying out a substrate polishing method according to
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Table 1 is a table showing an example of a relationship
between a flow of polishing processes of the polishing apparatus
according to the present invention and the kind of abrasive
grain/slurry, the top ring pressing force and the top ring
revolution number used;
[0040] Table 2 is a table showing a relationship between polishing
processes of the substrate polishing method according to the
present invention and polishing conditions;
[0041] Table 3 is a table showing an example of uniformity in
substrate polishing effected by a conventional substrate polishing
method; and
[0042] Table 4 is a table showing an example of uniformity in
substrate polishing effected by the substrate polishing method
according to the present invention.
[0043] The present invention will now be explained in connection
with embodiments thereof with reference to the accompanying
drawings. FIG. 2 is a plan view showing a substrate processing
apparatus having a substrate polishing apparatus according to the
present invention. The substrate polishing apparatus includes a
load/unload portion 1, a first robot 2, second cleaning machines 3,
4, a reverse rotation machine 5, a reverse rotation machine 6, a
second robot 7, first cleaning machines 8, 9, a first polishing
device 10 and a second polishing device 11.
[0044] The polishing device 10 includes a polishing table 10-1, a
top ring 10-2, a top ring head 10-3, a film thickness measuring
device 10-4, a pusher 10-5 and a dresser 10-10. Further, the
polishing device 11 includes a polishing table 11-1, a top ring
11-2, a top ring head 11-3, a film thickness measuring device 11-4,
a pusher 11-5 and a dresser 11-10.
[0045] Further, a drying condition film thickness measuring device
13 for measuring a film thickness in a drying condition after
polishing is disposed in the vicinity of the first robot 12.
[0046] In the substrate processing apparatus having the
above-mentioned arrangement, a semiconductor substrate W on which a
feed seed layer 107 and a plating film layer 106 were formed is set
in a cassette 1-1 to rest it on a load port of the load/unload
portion 1. The semiconductor substrate W is picked up from the
cassette by the first robot 2, and the substrate is transferred to
the reverse rotation machine 5 or the reverse rotation machine 6.
In this case, the surface of the semiconductor substrate W on which
the plating film layer 106 was formed is directed upwardly, and the
surface on which the plating film layer 106 was formed is turned
over by the reverse rotation machine 5 or the reverse rotation
machine 6 to be directed downwardly.
[0047] The semiconductor substrate W turned over by the reverse
rotation machine 5 or the reverse rotation machine 6 is picked up
by the second robot 7, and the semiconductor substrate W is rested
on the pusher 10-5 of the polishing device 10 or the pusher 11-5 of
the polishing device 11. The semiconductor substrate W is picked up
by the top ring 10-2 or the top ring 11-2, a surface to be polished
of the semiconductor substrate W is urged against a polishing
surface of the polishing table 10-1 or the polishing table 11-1,
and then the polishing is effected.
[0048] FIG. 3 is a view showing a schematic construction of the
polishing device 10 according to the present invention. As shown,
the polishing device 10 has the polishing table 10-1 rotated by a
motor M1 and the top ring 10-2 rotated by a motor M2. The polishing
table 10-1 and the top ring 10-2 are designed so that the numbers
of revolutions thereof can be changed by a control portion 20.
Further, the top ring head 10-3 can be turned around a rotary shaft
10-8 to be positioned above the polishing table 10-1 or above the
film thickness measuring device 10-4 or above the pusher 10-5.
[0049] The polishing surface 10-1a of the polishing table 10-1 is
constituted by foam polyurethane or material in which abrasive
grain is secured or impregnated. As abrasive grain for grinding or
for abrasive liquid supplied from a polishing liquid supply nozzle
10-6, silica is used. As an oxidizing agent, a material capable of
oxidizing copper (Cu), such as hydrogen peroxide water or ammonia,
is used. The polishing table 10-1 and a slurry or dressing water
are temperature-adjusted to keep the chemical reaction speed
constant. In particular, the polishing table 10-1 is formed from
alumina or ceramic such as SiC having a good heat transferring
ability, and a temperature-adjustment water pipe 10-7 is provided
to supply temperature-adjustment water in the interior of the
table.
[0050] The top ring head 10-3 can be shifted upwardly and
downwardly by a vertical direction driving mechanism 10-9, so that
the semiconductor substrate W held by the top ring 10-2 can be
urged against the polishing table with any pressing force by
changing the pressing force under the control of the control
portion 20. Further, as the film thickness measuring device 10-4
used for detecting an end point of the film thickness, an eddy
current type or an optical type which will be described later is
used to effect film thickness measurement of the copper plating
film layer 106 and the copper feed seed layer 107 or detection of a
film surface of a barrier layer 105 and an insulation film 102. The
detection output is transferred to the control portion 20. Further,
a surface temperature of the polishing surface 10-1a is detected by
a radiation thermometer 10-12, and the detection output is
transferred to the control portion 20. Incidentally, since the
construction of the polishing device 11 is the same as the
polishing device 10, explanation thereof will be omitted.
[0051] The polishing is effected through plural polishing
processes. In a first polishing process, the copper plating film
layer 106 is polished. A main purpose of the polishing in the first
polishing process is to remove a difference, i.e., unevenness, and,
in this case, a slurry having a good unevenness removing ability is
used. For example, a slurry capable of reducing an initial
unevenness of 700 nm of the copper plating film layer 106, having a
film thickness of about 100 .mu.m, to 20 nm or less is used. In
this case, the control portion 20 utilizes a polishing condition
improving the unevenness removing ability by reducing the load for
pressing the semiconductor substrate W against the polishing
surface 10-1a of the polishing table 10-1 in a second polishing
process to one half or less of the pressing force in the first
polishing process. The control of the load is effected by
controlling the vertical direction driving mechanism 10-9 by means
of the control portion 20.
[0052] As the film thickness measuring device 10-4 for detecting an
end point of the film thickness in the second polishing process,
when the copper plating film layer 106 remains at a thickness of
500 nm or more, a film thickness measuring device of the eddy
current type is used, and, when the layer 106 remains at a
thickness smaller than 500 nm or when the layer is removed until
the surface of the barrier layer 105 is exposed, a film thickness
measuring device of the optical type is used.
[0053] Although the barrier layer 105 is polished after the
polishing of the copper plating film layer 106 is finished, if the
barrier layer 105 cannot be abraded by the initially used slurry,
the composition of the slurry must be changed. Thus, the slurry
used in the first and second polishing processes and remaining on
the polished surface upon completion of the second polishing
process is cleaned and removed by water polishing or water jet or
atomizer or dresser, and then the third polishing process is
started.
[0054] FIG. 4 is a view showing a cleaning mechanism for cleaning
the polishing surface 10-1a of the polishing table 10-1. As shown,
a plurality (four in the illustrated embodiment) of mixing and
injecting nozzles (atomizers) 10-11a to 10-11d for mixing pure
water and nitrogen gas and for injecting the mixture are disposed
above the polishing table 10-1. To each of the mixing and injecting
nozzles 10-11a to 10-11d, nitrogen gas, the pressure of which is
adjusted by a regulator 16, is supplied from a nitrogen gas supply
source 14 through an air operator valve 18 and pure water, the
pressure of which is adjusted by a regulator 17, is supplied from a
pure water supply source 15 through an air operator valve 19.
[0055] Regarding the mixed gas and liquid, by altering parameters
such as pressure and temperature of the liquid and/or gas and
nozzle configuration by means of the injecting nozzle, the liquid
to be supplied is changed by the nozzle injection to {circle around
(1)} fine liquid droplets, {circle around (2)} fine solidified
particles or {circle around (3)} vaporized gas droplets (here,
{circle around (1)}, {circle around (2)} and {circle around (3)}
are referred to as "fog" or "atomize"), and the mixture of liquid
based component and gas component is injected toward the polishing
surface of the polishing table 10-1 with predetermined
orientation.
[0056] When the polishing surface 10-1a is reproduced (dressed) by
the relative movement between the polishing surface 10-1a and the
dresser 10-10 obtained by sliding them, the mixture fluid comprised
of pure water and nitrogen gas is injected toward the polishing
surface 10-1a from the mixture injecting nozzles 10-11a to 10-11d,
thereby cleaning the polishing surface. The pressure of the
nitrogen gas and the pressure of the pure water can be set
independently. In the illustrated embodiment, although both the
pure water line and the nitrogen gas line include manually driven
regulators, these lines may include regulators capable of changing
a set pressure on the basis of an external signal. As a result of
the cleaning of the polishing surface 10-1a by using the
above-mentioned cleaning mechanism, it was found that, by effecting
the cleaning for 5 to 20 seconds, slurry and polished residual
matters remaining on the polishing surface after the first and
second polishing processes can be removed. Incidentally, although
not shown, a cleaning mechanism having the same construction as the
cleaning mechanism shown in FIG. 4 is provided to clean the
polishing surface 11-1a of the polishing device 11.
[0057] In the above-mentioned description, an example that the
atomizer and the mechanical dressing are effected simultaneously
was explained. However, the atomizer, mechanical dressing, water
polishing and water jet may be effected independently or effected
with appropriate combinations thereof. The mechanical dressing used
here generally is effected by using a diamond dresser designed so
that a strip-shaped protruded portion to which diamond particles
are electrically adhered is provided along a circumferential area
on an under surface of the disk-shaped dresser 10-10 shown in FIG.
4. When the mechanical dressing is effected, both the setting and
the cleaning of the polishing surface can be achieved. Other than
the diamond dresser, a dresser designed to include a nylon brush
can be used.
[0058] The water polishing means that, in place of the slurry
supplied from the polishing liquid supply nozzle 10-6, pure water
is used, and the polishing is effected under the supply of pure
water while contacting the semiconductor substrate W with the
polishing surface 10-1a as shown in FIG. 3. When the water
polishing is performed, the pressing force of the top ring 10-2 is
made smaller in comparison with the first and second polishing
processes. By performing the water polishing, the polishing liquid
used in the first and second polishing processes and remaining on
the polishing surface is replaced by the pure water, thereby
cleaning the polishing surface 10-1a.
[0059] FIG. 5 is a view showing a construction of a cleaning
mechanism for cleaning the polishing surface 10-1a of the polishing
table 10-1 by using a water jet. As shown, a dressing unit 10-13 is
provided, and the dressing unit 10-13 includes a plurality (six in
the illustrated embodiment) of water jet nozzles 10-13c disposed
equidistantly along a radial direction above the polishing surface
10-1a of the polishing table 10-1. Each water jet nozzle 10-13c is
secured to a water jet nozzle arm 10-13a having flow paths 10-13b
therein.
[0060] The pure water pressurized by a pump 23 is supplied to the
water jet nozzles 10-13c through a tube 22, and the water jets are
injected from the water jet nozzles 10-13c toward the polishing
surface 10-1a. Water pressure of the water jet nozzle arm 10-13a is
adjusted by a control portion (not shown) for the pump 23 to be
maintained at a predetermined pressure. Further, the water jet
nozzle arm 10-13a has the same construction so that injecting
pressures and injecting speeds of water jets from the respective
nozzles becomes substantially the same as each other. The pressure
of the water jets can be maintained within a predetermined pressure
range from 5 to 30 kg/cm.sup.2 by controlling the pump 23.
[0061] Table 1 shows a relationship between a flow of first to
third polishing processes and the kind of abrasive grain/slurry,
the top ring pressing force and the top ring revolution number used
in the polishing processes. As shown in Table 1, in the first
polishing process, silica and copper polishing slurry are used as
abrasive grain and slurry, and the top ring pressing force is set
to 400 g/cm.sup.2 and the top ring revolution number (number of
revolutions of the top ring) is set to 70 rpm. In the next, second,
polishing process, silica and copper polishing slurry are used as
abrasive grain and slurry, and the top ring pressing force is set
to 200 g/cm.sup.2 and the top ring revolution number is set to 70
rpm. It is ascertained whether the copper plating film layer 106
and the feed seed layer 107 are removed or not by using the end
point measurement.
[0062] After it has been ascertained that the copper plating film
layer 106 and the feed seed layer 107 are polished and removed by
the end point measurement, the slurry used in the first and second
polishing processes and remaining on the polishing surface 10-1a is
cleaned and removed by the water polishing or the water jet or the
atomizer or the dresser, and then the third polishing process is
started. In the third polishing process, silica and Ta polishing
slurry are used as abrasive grain and slurry, and the top ring
pressing force is set to 200 g/cm.sup.2 and the top ring revolution
number is set to 50 rpm.
[0063] It is desirable that the abrasive grain used in the slurry
for polishing the barrier layer 105 in the third polishing process
is the same as the abrasive grain used in polishing the copper
plating film layer 106 and the feed seed layer 107 in the first and
second polishing processes. Further, the pH of a reagent (for
example, an oxidizing agent) added to the polishing liquid or
slurry in the respective polishing processes is offset toward
either the acidic side or the alkaline side in each polishing
process. By using such polishing liquid, the residual matters
remaining on the cloth constituting the polishing surface 10-1a in
the first and second polishing processes are prevented from
reacting to the polishing liquid used in the third polishing
process to form a compound.
[0064] As a result of tests, it was found that when the silica used
in both polishing processes are on the alkaline side or when the
silica is on the acidic side, both cases lead to good results. In
the film thickness end point detection in the third polishing
process, since the film thickness is small, the film thickness
measuring device of an optical type is used to detect the remainder
of the barrier layer 105, and a detection signal is sent to the
control portion 20. Incidentally, in the polishing using fixed
abrasive grains (abrasive grain dispersed and fixed in binding
agent), the slurry is not used as the polishing liquid, but reagent
liquid or pure water is supplied to effect the polishing.
[0065] In this case, it is preferable that the polishing liquid
used in the first and second polishing processes and the polishing
liquid used in the third polishing process are both on the alkaline
side or both on the acidic side. Polishing liquids representing a
pH on the same side with respect to pH 7 are desirable. However,
when neutral polishing liquid is used, in each polishing process,
combinations of neutral/neutral, neutral/alkaline and
neutral/acidic can be considered. The important matter is that the
acidic polishing liquid and the alkaline polishing liquid are not
used simultaneously on the same polishing table.
[0066] Incidentally, the abrasive grain used in the first and
second polishing processes and the abrasive grain used in the third
polishing process do not cause any problem even if the particle
diameters thereof are different from each other. Further, while an
example in which the slurry (liquid in which abrasive grain is
suspended) is used as the polishing liquid was explained, the
polishing liquid is not limited to the slurry. For example, in the
third polishing process, the polishing can be effected only by
using reagent liquid not including abrasive grain, and, in this
case, there is a problem regarding only the pH of the polishing
liquid used in the first and second polishing processes and the pH
of the polishing liquid used in the third polishing process. That
is to say, in the series of polishing processes, the polishing
liquids should be standardized to the acidic side or the alkaline
side.
[0067] Further, although not shown, the film thickness measuring
devices 10-4, 11-4 disposed in the vicinity of the polishing table
10-1 of the polishing device 10 and the polishing table 11-1 of the
polishing device 11 are constituted by film thickness measuring
devices having image processing devices, so that the film thickness
measured by each film thickness measuring device is stored as a
working record of the semiconductor substrate W and/or judgement is
effected whether or not the polished semiconductor substrate W can
be transferred to the next process. Further, if a predetermined
polished amount is not attained after the polishing is finished,
the polishing is performed again. Further, if the excessive amount
is polished for any abnormal reason, the apparatus is stopped to
not perform the next polishing, thereby preventing the number of
poor parts from being increased.
[0068] As mentioned above, since the first to third polishing
processes can be carried out on the single polishing table 10-1 or
11-1, the number of polishing tables can be reduced, thereby making
the entire apparatus more compact and enhancing through-put of the
substrate polishing.
[0069] After the polishing is finished, the semiconductor substrate
W is returned to the pusher 10-5 or 11-5 by the top ring 10-2 or
11-2, and then, the semiconductor substrate W is picked up by the
second robot 7 to bring it into the first cleaning machine 8 or 9,
and primary cleaning is effected. In this case, reagent liquid may
be injected onto the front and rear surfaces of the semiconductor
substrate W resting on the pusher 10-5 or 11-5 to remove the
particles and/or to treat such surfaces so that the particles have
difficulty adhering to such surfaces.
[0070] In the primary cleaning using the first cleaning machine 8
or 9, the front and rear surfaces of the semiconductor substrate W
are subjected to scrub cleaning. FIG. 6 shows a construction of the
first cleaning machine 8. As shown, in the first cleaning machine
8, the semiconductor substrate W is pinched by a plurality of
substrate rotating rollers 8-1 to rotate in a horizontal plane.
Rotating PVA sponge rolls 8-2 are provided so that they can be
urged against the front and rear surfaces of the semiconductor
substrate W. Further, cation water nozzles 8-4 having ultrasonic
oscillators 8-3 and DHF nozzles 8-5 are disposed above and below
the semiconductor substrate W. In order to remove the particles,
pure water, a surface-active agent, a chelate agent and/or a pH
adjusting agent are supplied onto the surfaces of the semiconductor
substrate W, and the scrub cleaning is effected by using the PVA
sponge rolls 8-2. Strong reagent liquid such as DHF is sprayed onto
the rear surface of the semiconductor substrate W to effect etching
of diffused copper, or, when there is no diffusion, the rear
surface of the semiconductor substrate is subjected to the scrub
cleaning by using the same reagent liquid as that used on the front
surface. Incidentally, the first cleaning machine 9 has the same
construction as the first cleaning machine 8.
[0071] After cleaning by using the first cleaning machine 8 or 9,
the semiconductor substrate W is picked up by the second robot 7,
and then the substrate is transferred to the reverse rotation
machine 5 or 6, where the semiconductor substrate W is turned over.
The semiconductor substrate is picked up from the reverse rotation
machine 5 or 6 by the first robot 2, and the semiconductor
substrate is sent to the second cleaning machine 3 or 4, where
secondary cleaning is effected. Although not shown, the second
cleaning machine 3 or 4 has the same construction as the first
cleaning machines 8, 9. Further, pure water, a surface-active
agent, a chelate agent and/or a pH adjusting agent may be supplied
and the surface may be cleaned by a pencil sponge. Thereafter, spin
drying is performed and then the semiconductor substrate W is
picked up by the first robot 2.
[0072] When the film thickness is measured by the film thickness
measuring device 10-4 or 11-4 disposed in the vicinity of the
polishing table 10-1 or 11-1, the first robot 2 returns the
semiconductor substrate W onto the cassette rested on the unload
port of the load/unload portion 1. When the multi-layer film
measurement is performed, since the measurement must be performed
under a dried condition, the film thickness is measured by the
dried condition film thickness measuring device 13. Then the
measured film thickness is stored as a working record of the
semiconductor substrate W and/or a judgement is effected whether or
not the polished semiconductor substrate can be transferred to the
next process.
[0073] FIG. 7 is a perspective view of the second robot 7. As
shown, the second robot 7 has two upper and lower hands 7-1, and
the hands 7-1 are attached to distal ends of respective arms 7-2 so
that they can be turned. The semiconductor substrate W is dipped up
by the hands 7-1 (semiconductor substrate W is dropped down), so
that the semiconductor substrate can be transferred to a desired
position.
[0074] FIG. 8 is a view showing the construction of the film
thickness measuring device provided on the polishing device 10 and
adapted to measure the film thickness of the semiconductor
substrate W being polished. As shown, a film thickness measuring
device 10-14 of the eddy current type and a film thickness
measuring device 10-15 of the optical type are provided within the
polishing table 10-1 and serve to measure the film thickness of the
polished surface of the semiconductor substrate held by the top
ring 10-2 and being polished.
[0075] In the film thickness measuring device 10-14 of the eddy
current type, eddy current is generated in conductive films (copper
plating film layer 106 and feed seed layer 107) of the
semiconductor substrate W by applying high frequency electrical
current to a sensor coil. Since the eddy current is changed in
accordance with the film thickness, the film thickness is measured
by monitoring the combined impedance with a sensor circuit.
[0076] On the other hand, the film thickness measuring device 10-15
of the optical type has a light emitting element and a light
receiving element and is designed so that light from the light
emitting element is illuminated onto the surface to be polished of
the semiconductor substrate W and light reflected from the surface
to be polished is received by the light receiving element. As the
conductive film (Cu film) of the semiconductor substrate W reaches
a predetermined film thickness, a part of the light illuminated
from the light emitting element onto the surface to be polished is
permeated through the conductive film, with the result that there
exist two lights, i.e., reflected light reflected from the
oxidation film (SiO.sub.2) underlying the conductive film and
reflected light reflected from the surface of the conductive film.
By receiving such two lights by means of the light receiving
element and by processing such lights, the film thickness is
measured.
[0077] Next, another embodiment of the present invention will be
explained. Incidentally, in an embodiment which will be described
hereinbelow, while an example that a Ti film, a TiN film and a W
film successively laminated on an oxidation film of a silicon
substrate is explained, of course, the films polished by a
substrate polishing method according to the present invention are
not limited to such films.
[0078] FIG. 9 is a view showing a construction of a substrate
polishing apparatus carrying out the substrate polishing method
according to the present invention. In FIG. 9, a polishing cloth
202 is adhered to an upper surface of a polishing table 201 which
is in turn rotated by a polishing table driving motor 203 in a
direction shown by the arrow A. A top ring 205 for holding a
substrate 204 is rotated while pressing the substrate against the
upper surface of the polishing cloth 202, and this top ring is
attached to a rotary shaft 206 and is rotatably supported via a
bearing 207. The rotary shaft 206 is rotated by a top ring driving
motor 209 via a gearing mechanism 208.
[0079] An urging cylinder 210 serves to urge the top ring 205
holding the substrate 204 against the upper surface of the
polishing cloth 202 of the polishing table 201. Further, a slurry
supply nozzle 211 for supplying slurry to the upper surface of the
polishing cloth 202 is connected to a slurry supply source (not
shown) via an open/close valve 213. A water supply nozzle 212 for
supplying water to the upper surface of the polishing cloth 202 is
connected to a water supply source (not shown) via an open/close
valve 214. A control device 215 serves to receive a current
detection signal I1 of the polishing table driving motor 203
detected by a current sensor 216, a current detection signal I2 of
the top ring driving motor 209 detected by a current sensor 217, a
film thickness detection signal S1 detected by an optical film
thickness sensor 218, and a film thickness detection signal S2
detected by a film thickness sensor 219 of eddy current type.
[0080] Further, the control device 215 serves to control the urging
cylinder 210, thereby controlling the pressing force (substrate
pressing load) applied to the top ring 205 and to control the
polishing table driving motor 203 and the top ring driving motor
209, thereby controlling a rotational speed N1 of the polishing
table 201 and a rotational speed N2 of the top ring 205.
[0081] In the substrate polishing apparatus having the
above-mentioned construction, the substrate polishing method
according to the present invention serves to perform the polishing
through three or more polishing processes in which at least one of
the substrate pressing load for pressing the substrate 204 against
the upper surface of the polishing cloth 202 of the polishing table
201, the number of revolutions of the polishing table 201 and the
top ring 205, and the polishing liquid (slurry, water, mixture of
water and inert gas or the like) is changed.
[0082] Table 2 shows a concrete relationship between the polishing
processes and the polishing conditions. Here, as shown in FIGS.
1(d) and 1(e), the substrate on which an oxidation film 301, a Ti
film 302, a TiN film 303 and a W film 304 was successively
laminated is polished, and the polishing is performed through steps
1 to 6 (polishing processes). Further, the numbers of revolutions
of the polishing table and the top ring 205 are set to be constant,
and the polishing conditions in the respective polishing processes
are selected as follows.
[0083] In the step 1, slurry is used as the polishing liquid and
the substrate pressing load is set to 500 kgf/cm.sup.2. In the step
2, slurry is used as the polishing liquid and the substrate
pressing load is set to 400 kgf/cm.sup.2. In the step 3, slurry is
used as the polishing liquid and the substrate pressing load is set
to 200 kgf/cm.sup.2. In the step 4, water is used as the polishing
liquid and the substrate pressing load is set to 50 kgf/cm.sup.2.
In the step 5, slurry is used as the polishing liquid and the
substrate pressing load is set to 100 kgf/cm.sup.2, and in the step
6, water is used as the polishing liquid and the substrate pressing
load is set to 50 kgf/cm.sup.2. In the various steps, the same type
of slurry is used, and multi-polishing is effected on the same
polishing table while changing only the load.
[0084] In the substrate polishing apparatus shown in FIG. 9,
execution of the steps 1 to 6 (polishing processes) will be
explained. By the control of the control device 215, the polishing
table 201 and the top ring 205 are rotated with a predetermined
number of revolutions (rotational speeds) the pressing force, i.e.,
substrate pressing load applied to the top ring 205, is set to 500
kgf/cm.sup.2 by controlling the urging cylinder 210, and the
polishing is effected for 10 seconds (polishing of step 1). Then,
the substrate pressing load is changed to 400 kgf/cm.sup.2, and the
polishing is effected for 30 seconds (polishing of step 2). Then,
the substrate pressing load is changed to 200 kgf/cm.sup.2, and the
polishing is effected for 60 seconds (polishing of step 3). In
these steps 1 to 3, the control device 215 opens the open/close
valve 213 (in this case, the open/close valve 214 is closed), with
the result that the slurry is supplied onto the upper surface of
the polishing cloth 202 through the slurry supply nozzle 211.
[0085] The polishing process regarding the step 3 is finished by
detection (end point detection) of the TiN film 303. When the W
film is polished and removed and the TiN film 303 abuts against the
polishing cloth 202, since the friction force is changed, the
electrical current of the polishing table driving motor 203 for
driving the polishing table 201 is also changed. The control device
215 can detect the TiN film 303 (end point detection) on the basis
of a change in current detection signal I1 of the polishing table
driving motor 203 detected by the current sensor 216. After the TiN
film 303 is detected, the open/close valve 214 is opened (in this
case, the open/close valve 213 is closed) to supply the water onto
the upper surface of the polishing cloth 202 through the water
supply nozzle 212, and, at the same time, the substrate pressing
load is changed to 50 kgf/cm.sup.2 by controlling the pressing
force of the urging cylinder 210, and water polishing is effected
(polishing of step 4).
[0086] The water polishing has a function for cooling high
temperature portions on the polishing surface of the polishing
cloth 202 and slurry and the polished surface of the substrate 204
heated by the slurry polishing with great substrate pressing load
in the steps 1 to 3, thereby suppressing polishing (erosion) of the
W film 304 to keep the uniformity of the polished surface of the
substrate 204.
[0087] After the water polishing is performed for a predetermined
time period, the open/close valve 213 is opened (in this case, the
open/close valve 214 is closed) to supply the slurry onto the upper
surface of the polishing cloth 202 through the slurry supply nozzle
211, and, at the same time, the substrate pressing load is changed
to 100 kgf/cm.sup.2 by controlling the pressing force of the urging
cylinder 210, and the slurry polishing is effected (polishing of
step 5). By such slurry polishing, the TiN film 303 and the Ti film
302 are polished and removed. The completion of the slurry
polishing in the step 5 is determined by the removal of the Ti film
302, i.e., detection (end point detection) of the oxidation film
301. Similar to the above, the detection of the oxidation film 301
can be effected by the control device 215 on the basis of change in
the current detection signal I1 of the polishing table driving
motor 203 detected by the current sensor 216.
[0088] After the polishing in the step 5 is finished, the control
device 215 opens the open/close valve 214 (in this case, the
open/close valve 213 is closed) to supply the water onto the upper
surface of the polishing cloth 202 through the water supply nozzle
212, and, at the same time, the substrate pressing load is changed
to 50 kgf/cm.sup.2 by controlling the pressing force of the urging
cylinder 210, and the water polishing is effected for a
predetermined time period (polishing of step 6).
[0089] As mentioned above, by effecting the slurry polishing in the
steps 1 to 3 while changing the substrate pressing load
(500.about.200 kgf/cm.sup.2), the uniformity of the polished
surface of the substrate 204 is improved in comparison with the
conventional polishing with the same load. Table 3 shows an example
of uniformity of substrate polishing achieved when the conventional
polishing is effected with the same substrate pressing load, and
Table 4 shows an example of uniformity of substrate polishing
(polishing according to the present invention) achieved when the
polishing is effected while changing the substrate pressing load as
in the steps 1 to 3. As apparent from Table 3 and Table 4, it can
be seen that the uniformity of the polished surface is improved by
the polishing of the present invention more than the conventional
polishing. Further, while oxide erosion was 40 to 50 nm in the
conventional case, in the present invention, it can be suppressed
to 20 nm or less.
[0090] As mentioned above, by effecting the slurry polishing to
remove the W film 304 while changing the substrate pressing load
(500.about.200 kgf/cm.sup.2) in the steps 1 to 3 and then by
effecting the water polishing in the step 4 and then by effecting
the slurry polishing with smaller load to remove the TiN film 303
and the Ti film 302 and, lastly, by effecting the water polishing
in the step 6, the oxide erosion can be improved, thereby enhancing
the uniformity of the polished surface of the substrate 204.
Further, since the plural polishing processes can be performed on
the same table, there is no loss time for changing the table, with
the result that the through-put of processing can be enhanced and
space can be saved.
[0091] Atomizer polishing in which the polishing is effected while
supplying a mixture of water and inert gas such as nitrogen onto
the upper surface of the polishing cloth 202 through the water
supply nozzle 212 may be added to the water polishing using the
water as the polishing liquid in the steps 4 and 6. Further,
although not shown, independently from the water supply nozzle 212,
a mixture supply nozzle may be additionally provided to supply the
mixture of water and inert gas onto the upper surface of the
polishing cloth 202 through the mixture supply nozzle under the
control of the control device 215.
[0092] Further, in the above description, while an example in which
the finishing point of the polishing process, i.e., the end point,
is detected on the basis of the change in the current detection
signal I1 of the polishing table driving motor 203 detected by the
current sensor 216 was explained, in place of this, the end point
may be detected on the basis of a change in the current detection
signal I2 of the top ring driving motor 209 detected by the current
sensor 217. That is to say, when the film thickness of the polished
surface of the substrate 204 is changed, since the friction force
between the polished surface of the substrate 204 and the polishing
surface of the polishing cloth 202 is changed, and, thus, the
current I2 of the top ring driving motor 209 for driving the top
ring 205 is also changed, the end point can be detected on the
basis of the change in current. However, if the holding force (for
example, vacuum absorbing force) of the top ring 205 for holding
the substrate 204 is weak so that the substrate 204 is rotated with
respect to the top ring 205, the end point cannot sometimes be
detected correctly.
[0093] Further, in the above description, while an example in which
the end point is detected on the basis of the change in the current
detection signal I1 of the polishing table driving motor 203 or the
change in the current I2 of the top ring driving motor 209 was
explained, when the friction force is changed, since vibration or
sound of the polishing table and/or the top ring 205 is also
changed, by monitoring such vibration or sound, the end point may
be detected on the basis of the change in such vibration or
sound.
[0094] Further, an optical film thickness sensor 218 or a film
thickness sensor 219 of the eddy current type may be provided in
the polishing table 201 so that the film thickness is detected
whenever the optical film thickness sensor 218 or the film
thickness sensor 219 of the eddy current type is passed through the
under surface of the polished surface of the substrate 204 by the
rotation of the polishing table 201, and detection output is sent
to the control device 215 which in turn detects the end point on
the basis of the film thickness detection output.
[0095] Incidentally, the optical film thickness sensor 218 has a
light emitting element and a light receiving element and is
designed so that light from the light emitting element is
illuminated onto the polished surface of the substrate 204 and
light reflected from the polished surface is received by the light
receiving element and the film thickness is measured on the basis
of the received light. In this case, the light emitted from the
light emitting element may be a laser beam or light from a light
emitting diode (LED). On the other hand, the film thickness sensor
219 of eddy current type has a sensor coil and is designed so that
eddy current is generated in the conductive film of the polished
surface of the substrate 204 by applying high frequency electrical
current to the sensor coil and, since the eddy current is changed
in accordance with the film thickness, by monitoring composite
impedance with a sensor circuit, the film thickness is
measured.
[0096] Incidentally, in the above description, while an example in
which the substrate, having the oxidation film 301 on which the Ti
film 303, TiN film 302 and W film 304 were successively laminated,
is polished, was explained, the substrate polishing method
according to the present invention is not limited to such an
example, but, for example, can be applied to the polishing of a
substrate having an oxidation film on which a barrier layer and a
copper (Cu) film are formed.
[0097] Further, in the above description, while an example that the
polishing is performed while changing the substrate pressing load
and/or the polishing liquid (slurry, water, mixture of water and
inert gas) was explained, other than this, for each polishing
process, the number of revolutions of the polishing table and/or
the number of revolutions of the top ring may be changed.
[0098] The present description and attached drawings depict
embodiments wherein a top ring as well as a polishing table are
independently rotated, but the present invention is not limited to
only such embodiments, and in case that a polishing surface moves
reciprocally or in orbital motions, it is possible to change
relative speed between the top ring and the polishing table by
changing the transfer speed of the polishing surface.
[0099] Further, in the above description, while an example that the
polishing cloth 202 is adhered to the upper surface of the
polishing table 201 was explained, in the substrate polishing
method according to the present invention, a grinding stone plate
may be attached to the upper surface of the polishing table 201.
Incidentally, in this case, generally, since water (rather than the
slurry) is used as the polishing liquid, in this case, the
polishing liquid (water) is not changed between the polishing
processes.
[0100] As mentioned above, according to the present invention, the
following excellent effects can be achieved.
[0101] Since the substrate polishing is effected on the same
polishing table, the number of polishing tables can be reduced, and
at the same time, the through-put (processing amount per unit time)
for the substrate polishing can be enhanced.
[0102] According to the present invention, by effecting the
polishing through three or more polishing processes in which at
least one of the substrate pressing load, the relative speed
between the polishing table and the substrate and the polishing
liquid is changed, i.e., the polishing conditions are changed (for
example, the substrate pressing load is changed), the uniformity of
the polished surface can be improved in comparison with the prior
art.
[0103] According to the present invention, since the completion of
the polishing process is determined by the detection of the film
thickness, for example, after the polishing of a certain film is
finished, when the polishing of another film is started, the
polishing conditions (for example, polishing liquid, substrate
pressing load) can be changed to suit such polishing.
[0104] According to the present invention, by adding the water
polishing and/or the atomizer polishing after the last polishing
process, since the high temperature portions of polished surface of
the substrate and the polishing surface of the polishing table
heated in the preceding process can be cooled and at the same time
the polishing liquid used in the preceding process can be removed,
the erosion of the polished surface of the substrate can be
prevented, thereby enhancing the uniformity.
[0105] According to the present invention, by polishing the
substrate on which the W film was formed through three or more
polishing processes, for example, while changing the substrate
pressing load, the uniformity of the polished surface can be
improved in comparison with the prior art.
* * * * *