U.S. patent application number 11/898211 was filed with the patent office on 2008-03-13 for polishing apparatus, polishing pad, and polishing method.
This patent application is currently assigned to NEC ELECTRONICS CORPORATION. Invention is credited to Shoji Fujitani.
Application Number | 20080064302 11/898211 |
Document ID | / |
Family ID | 39170300 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080064302 |
Kind Code |
A1 |
Fujitani; Shoji |
March 13, 2008 |
Polishing apparatus, polishing pad, and polishing method
Abstract
A polishing pad is placed on a polishing apparatus including a
polishing platen which is rotatable and on which the polishing pad
is placed, a substrate retaining mechanism, and a supplying
mechanism for supplying a polishing agent on an upper surface of
the polishing pad, the polishing pad having grooves extending from
the center of the polishing pad to the outer edge thereof, the
groove becoming gradually deeper from the center of the polishing
pad toward the outer edge portion thereof so that the depth of the
groove is the largest at the outer edge portion, thereby allowing a
slurry to be smoothly discharged from the upper surface of the
polishing platen.
Inventors: |
Fujitani; Shoji; (Yamaguchi,
JP) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY LAW GROUP, PLLC
8321 OLD COURTHOUSE ROAD, SUITE 200
VIENNA
VA
22182-3817
US
|
Assignee: |
NEC ELECTRONICS CORPORATION
Kawasaki
JP
|
Family ID: |
39170300 |
Appl. No.: |
11/898211 |
Filed: |
September 10, 2007 |
Current U.S.
Class: |
451/41 ;
451/527 |
Current CPC
Class: |
B24B 37/26 20130101 |
Class at
Publication: |
451/41 ;
451/527 |
International
Class: |
B24B 7/30 20060101
B24B007/30; B24D 11/00 20060101 B24D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2006 |
JP |
245465/2006 |
Claims
1. A polishing pad, having a plurality of grooves extending from
center to edge of the polishing pad, wherein the groove has a depth
becoming larger from the center of the polishing pad toward edge
portion and largest at the edge portion.
2. A polishing pad as claimed in claim 1, wherein the depths of the
groove is gradually increased.
3. A polishing pad as claimed in claim 1, wherein the depths of the
groove is stepwisely increased.
4. A polishing pad as claimed in claim 1, wherein the plurality of
grooves are provided in grid like fashion onto the surface of the
polishing pad.
5. A polishing pad as claimed in claim 1, wherein the plurality of
grooves are provided onto the surface of the polishing pad radially
from the center of the polishing pad.
6. A polishing pad as claimed in claim 1, wherein the plurality of
grooves are provided onto the surface of the polishing pad in a
form of curved line extending from center to edge of the polishing
pad.
7. A polishing pad as claimed in claim 1, wherein the grooves are
taper-shape having bottom portions that are narrower than their top
portions.
8. A polishing apparatus, comprising: a polishing pad; a polishing
platen which is rotatable and on which the polishing pad is placed;
a substrate retaining mechanism; and a supplying mechanism for
supplying a polishing agent on upper surface of the polishing pad,
wherein the polishing pad has a plurality of grooves extending from
center to edge of the polishing pad; the grooves have a depth
gradually becoming larger from the center of the polishing pad
toward edge portion and largest at the edge portion.
9. A method of polishing a substrate, comprising the steps of:
placing the polishing pad according to claim 1 on a polishing
platen; retaining the substrate; pressing the substrate to the
polishing pad; supplying a polishing agent to upper surface of the
polishing pad; rotating the polishing platen; and rotating the
substrate.
10. A polishing pad comprising a body having a center part and a
peripheral part, and a plurality of grooves selectively formed in
the body with a first depth at the center part and a second depth
at the peripheral part, the first depth being smaller than the
second depth.
11. The pad as claimed in claim 10, wherein the first depth is
changed stepwisely from the second depth.
12. The pad as claimed in claim 10, wherein the first depth is
changed gradually from the second depth.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing apparatus for
polishing a surface of a semiconductor substrate by a chemical
mechanical polishing (CMP) method, a polishing pad for use in the
polishing apparatus, and a polishing method using the polishing
pad.
[0003] 2. Description of the Related Art
[0004] In order to flatten irregularities on a surface of a
semiconductor substrate in a manufacturing process of the
semiconductor substrate or a manufacturing process of a
semiconductor device, a chemical mechanical polishing (CMP) method
is performed. For the chemical mechanical polishing method, a CMP
apparatus 2 as shown in FIGS. 1 and 2 is used. The CMP apparatus 2
includes a polishing platen 4, a spindle carrier 8, a spindle 10,
and a slurry nozzle 14. To an upper surface of the polishing platen
4, a polishing pad 6 is adhered. The spindle carrier 8 retains a
wafer 12, that is, a semiconductor substrate, and presses the wafer
12 to the polishing pad 6 at a constant load. The slurry nozzle 14
drops the muddy slurry 16 including a polishing agent on an upper
surface of the polishing pad 6. The polishing platen 4 and the
spindle 10 are rotated by a rotation mechanism (not shown). The CMP
apparatus 2 includes two sets of the spindle carriers 8 and the
spindles 10 such that two wafers 12 can be polished at the same
time. The two spindles 10 are connected to a structural body called
a bridge 18.
[0005] In a polishing process for a surface of the wafer 12, the
polishing agent in the slurry 16 is kept in minute holes (around 10
to 50 .mu.m in diameter) on the surface of the polishing pad 6 and
irregularities on the surface of the wafer 12 are smoothed by the
polishing agent.
[0006] FIG. 3 is a top view of the polishing pad 6. FIG. 4 is a
sectional view of the polishing pad 6. The polishing pad 6 has a
disk shape and is made of a synthetic resin such as polyurethane.
The polishing pad 6 has pad grooves 20 formed in a grid like
fashion. FIG. 4 is the sectional view taken along the line A-A' of
FIG. 3. A sectional shape of the pad grooves 20 is a U-shape. A pad
groove base portion 20a is a plane. A pad groove wall 20b is a wall
perpendicular to the pad groove base portion 20a.
[0007] A width W1 of the pad groove 20 and a depth D1 of the pad
groove 20 have the same dimensions independent of the position on
the pad. Further, a pitch P1 of the pad grooves 20 is constant, and
the pad grooves 20 are formed in grid like fashion.
[0008] Note that, the polishing pad 6 is composed of two layers,
that is, an upper layer polishing pad 6a and a lower layer
polishing pad 6b. The upper layer polishing pad 6a is formed with
the pad grooves 20.
[0009] By performing polishing, the minute holes on the surface of
the polishing pad 6 are worn out. Accordingly, the surface of the
polishing pad 6 is ground by a disk plate on which diamond
particles are electrodeposited, thereby creating a new surface
having minute holes. This is an operation for eliminating clogging
on the surface of the polishing pad 6. Thus, this operation enables
to polish the wafer 12 accurately in a stable manner.
[0010] Further, as long as the slurry 16 on the pad is fresh and
frequently replaced with supplying slurry, it is possible to polish
the wafer 12 in a stable manner. In other words, when the slurry 16
which has been supplied from the nozzle remains on the surface of
the polishing pad 6 and is not replaced with the fresh slurry 16 to
be supplied later, the wafer 12 cannot be polished. Further, for
accurately polishing the wafer 12, it is also important to
discharge the shavings produced during polishing smoothly from the
top surface of the polishing pad 6 to an outside through an outer
edge of the polishing pad 6.
[0011] JP 2001-121405 A discloses a polishing pad having a
structure in which a polishing surface of the polishing pad is
formed with grooves extending from an initial point in the vicinity
of a central portion of the polishing surface to an end point on an
outer edge of the polishing surface. The cross section of a groove
on the polishing pad varies between the initial point and the end
point, the cross section reaches the maximum value at a point
between the initial point and the end point.
[0012] JP 2005-183711 A discloses a polishing pad having a
plurality of parallel groove groups including substantially
straight grooves which are in parallel with each other in a
polishing surface. At least one of the grooves has different depths
within the same groove.
[0013] JP 2000-117620 A, JP 2004-327567 A, and U.S. Pat. No.
6,093,651 each discloses a technology of changing a depth of a
groove concentrically with respect to a polishing pad from a center
to an outer periphery thereof.
[0014] However, the inventor of the present invention has noticed
that there are the following problems with use in those polishing
pads.
[0015] In a case where a surface of the polishing pad 6 is roughly
divided from a center 6c toward an outer edge into a central
portion, a middle portion, and an outer edge portion, when an
operation of periodically grinding the polishing pad 6 with the
disk plate as described above and a normal operation of polishing
the wafer 12 are performed, the middle portion is worn down to a
maximum degree, so the surface of the polishing pad 6 corresponding
to the middle portion is recessed. In particular, in the operation
of grinding the polishing pad 6 with the disk plate, the middle
portion of the surface of the polishing pad 6 is worn down more
than in the other operation.
[0016] When the middle portion of the polishing pad 6 is worn, the
slurry 16 and the shavings produced by the polishing pad 6 are not
discharged to the outside, and remain in the middle portion. As a
result, the shavings generate minute flaws (micro scratches) on the
surface of the wafer 12. Further, when the slurry 16 which is not
discharged but remains on the pad, the slurry 16 is dried and then
the polishing agent included in the slurry 16 becomes coarse. The
coarse polishing agent may scratch the surface of the wafer 12,
thereby causing the micro scratches. Accordingly, in order to
ensure accuracy of a polished surface of the wafer 12 and to obtain
the uniform polished surface of the wafer 12, it is important to
improve discharging efficiency of the slurry 16.
[0017] However, in a case where the polishing pad 6 as shown in
FIG. 3 or 4 is used, the discharging efficiency of the slurry 16 is
not satisfactory. Therefore, there is a demand for the polishing
pad 6, the CMP apparatus 2, and the polishing method by which the
discharging efficiency of the slurry 16 is more satisfactory.
SUMMARY
[0018] According to the present invention, a polishing pad has
grooves extending from a center of the polishing pad to an outer
edge thereof, the groove becoming gradually deeper from the center
of the polishing pad toward an outer edge thereof such that a depth
of the groove is the largest at an outer edge portion. Further, the
polishing pad is placed on a polishing apparatus including a
rotatable polishing platen on which the polishing pad is placed, a
substrate retaining mechanism, and a supplying mechanism for
supplying a polishing agent on an upper surface of the polishing
pad, the polishing pad having the grooves extending from the center
of the polishing pad to the outer edge thereof, the groove becoming
gradually deeper from the center of the polishing pad toward the
outer edge portion thereof such that the depth of the groove is the
largest at the outer edge portion, thereby allowing a slurry to be
smoothly discharged from the upper surface of the polishing
platen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other objects, advantages and features of the
present invention will be more apparent from the following
description taken in conjunction with the accompanying drawings, in
which:
[0020] FIG. 1 is a schematic perspective view illustrating a CMP
apparatus;
[0021] FIG. 2 is a schematic side view illustrating the CMP
apparatus;
[0022] FIG. 3 is a top view of a polishing pad;
[0023] FIG. 4 is a sectional view of a polishing pad according to a
conventional technique;
[0024] FIG. 5A is a sectional view of a polishing pad according to
a first embodiment of the present invention;
[0025] FIG. 5B is a sectional view of the polishing pad according
to the first embodiment of the present invention;
[0026] FIGS. 6A and 6B are views for describing one-mode of pad
groove walls of the polishing pad according to the present
invention;
[0027] FIG. 7 is a sectional view of a polishing pad according to a
second embodiment of the present invention;
[0028] FIG. 8 is a top view of a polishing pad according to a third
embodiment of the present invention;
[0029] FIG. 9 is a sectional view of the polishing pad according to
the third embodiment of the present invention;
[0030] FIG. 10 is a top view of a polishing pad according to a
fourth embodiment of the present invention; and
[0031] FIG. 11 is a sectional view of the polishing pad according
to the fourth embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] The invention will be now described herein with reference to
illustrative embodiments. Those skilled in the art will recognize
that many alternative embodiments can be accomplished using the
teachings of the present invention and that the invention is not
limited to the embodiments illustrated for explanatory
purposes.
First Embodiment
[0033] FIGS. 5A and 5B show sectional views of a polishing pad 30
according to a first embodiment of the present invention. The
polishing pad 30 is made of a synthetic resin such as polyurethane.
Further, the polishing pad 30 has pad grooves 32 formed in grid
like fashion like in a polishing pad 6 shown in FIG. 3. The pad
grooves 32 are formed by mechanical machining. Further, FIG. 5A is
a sectional view taken along the line A-A' of FIG. 3. FIG. 5B is a
sectional view taken along the line B-B' of FIG. 3. Further, a
sectional shape of the pad groove 32 is a U-shape. A pad groove
base portion 32a is a flat plane. Pad groove walls 32b are walls
perpendicular to the pad groove base portion 32a. This sectional
shape is one example as described after.
[0034] A dimension of a groove width W30 of the pad groove 32 is
the same as that of the pad groove 32 in any place on the pad.
Further, a pitch P30 of the pad grooves 32 is also constant.
[0035] From a center 30c of the polishing pad 30 toward an outer
edge thereof, a depth of the pad groove 32 increases. That is, in
the vicinity of the center 30c of the polishing pad 30, the pad
groove 32 has a depth D2, in a middle portion between the center
30c and the outer edge, the pad groove 32 has a depth D3, and in
the outer edge, the pad groove 32 has a depth D4. As shown in FIG.
5B, when a surface of any pad grooves 32 is viewed in section, it
is understood that the pad grooves 32 has an inclined surface 32a'
toward the outer edge of the polishing pad 30 with the center 30c
of the polishing pad 30 being a highest point.
[0036] Note that, the polishing pad 30 is composed of two layers,
that is, an upper layer polishing pad 30a and a lower layer
polishing pad 30b. The pad grooves 32 are formed in the upper layer
polishing pad 30a.
[0037] As described above, the polishing pad 30 has a structure in
which the depth of the pad groove 32 increases from the center 30c
toward the outer edge. Accordingly, with a centrifugal force caused
by rotation of a polishing platen 4 and also with a function of the
inclined surface 32a' of the pad groove base portion 32, a slurry
16 and shavings produced by the polishing pad 30 can easily be
discharged. The outer edge of the polishing pad 6 corresponds to
lower portions of the inclined surface 32a', so the slurry 16 and
the shavings flow toward the outer edge. When the slurry 16 and the
shavings are easily discharged, anew slurry 16 supplied from a
slurry nozzle 14 is supplied to a polishing surface of a wafer 12,
thereby making it possible to prevent generation of micro
scratches. Note that, in addition to the pad grooves 32 formed in
the polishing pad 30, holes may further be formed therein.
[0038] A CMP apparatus 2 including the polishing pad 30 is used to
polish the wafer 12 in the following manner. First, the polishing
pad 30 is adhered on an upper surface of the polishing platen 4. A
spindle carrier 8 retains the wafer 12 and the spindle carrier 8
presses the wafer 12 to the polishing pad 30 at a constant load.
Through the slurry nozzle 14, from a storage container (not shown)
of the slurry 16, the slurry 16 is supplied to the upper surface of
the polishing pad 30 continuously or intermittently. The polishing
platen 4 rotates at a constant rotation speed and the spindle
carrier 8 also rotates at a constant rotation speed.
[0039] FIGS. 6A and 6B are views for describing another example of
pad groove walls of the polishing pad 30 according to the present
invention. FIGS. 6A and 6B are examples of pad groove 41
illustrating a shallow pad groove 44 and deep pad groove 46. In
correspondence with the above description made with reference to
FIGS. 5A and 5B, the shallow pad groove 44 having a depth D2'
indicates the pad groove 41 in the vicinity of the center 30c of
the polishing pad 32 and the deep pad groove 46 having a depth D4'
indicates the pad groove 41 in the vicinity of the outer edge of
the polishing pad 30. A width W3 of a base portion of the shallow
pad groove 44 is smaller than a width W2 of an upper portion
thereof, and pad groove walls 44a form inclined surfaces. Further,
a width W5 of a base portion of the deep pad groove 46 is smaller
than a width W4 of an upper portion thereof, and pad groove walls
46a form inclined surfaces. In this case, the width W2 and the
width W4 of the upper portions have the same dimension. The pad
grooves 41 are formed by mechanical machining.
[0040] As described above, the pad groove walls 44a and 46a of the
pad grooves 41 form the inclined surfaces, thereby making the
slurry 16 and the shavings produced by the polishing pad 30
difficult to remain in the pad grooves 41 and easily discharged.
That is, the inclined surfaces of the pad groove walls 44a and 46a
have an effect of preventing generation of the micro scratches on
the wafer 12.
Second Embodiment
[0041] FIG. 7 shows a sectional view of a polishing pad 40
according to a second embodiment of the present invention. The
polishing pad 40 is made of a synthetic resin such as polyurethane.
Further, the polishing pad 40 has pad grooves 42 formed in a grid
like fashion like in the polishing pad 6 shown in FIG. 3. The pad
grooves 42 are formed by mechanical machining. Further, FIG. 7 is a
sectional view taken along the line A-A' of FIG. 3. Further, a
sectional shape of the pad groove 42 is a U-shape. A pad groove
base portion 42a is a plane. Pad groove walls 42b are walls
perpendicular to the pad groove base portion 42a. Note that, as
shown in FIG. 6, in a sectional shape of the pad groove 42, the pad
groove walls 42b' may form the inclined surfaces.
[0042] A dimension of a groove width W40 of the pad groove 42 is
the same as that of the pad groove 42 in any place. Further, a
pitch P40 of the pad grooves 42 is also constant.
[0043] The polishing pad 40 has a structure in which the pad
grooves 42 are divided from an outer edge side into groups of a
first pad grooves 40d, a second pad grooves 40e, a third pad
grooves 40f, a fourth pad grooves 40g, and a fifth pad grooves 40h,
and a groove depth of the each group is set for each group. A depth
D5 of the first pad grooves 40d is the largest. The nearer the
group is to a center 40c, the smaller the groove depth is. For
example, the third pad grooves 40f have a depth D6. A depth D7 of
the fifth pad grooves 40h is the smallest.
[0044] Note that, the polishing pad 40 is composed of two layers,
that is, an upper layer polishing pad 40a and a lower layer
polishing pad 40b. The pad grooves 42 are formed in the upper layer
polishing pad 40a. Each of the upper layer polishing pad 40a and
the lower layer polishing pad 40b has a thickness of about 1 to 2
mm. The depth D5 of the first pad grooves 40d is 80% of a thickness
of the upper layer polishing pad 40a. The depth D6 of the third pad
grooves 40f is 60% of the thickness of the upper layer polishing
pad 40a. The depth D7 of the fifth pad grooves 40h is 40% of the
thickness of the upper layer polishing pad 40a.
[0045] As described above, the polishing pad 40 has a structure in
which the depth of the pad grooves 42 stepwisely increases from the
center 40c towards the outer edge. Accordingly, with a centrifugal
force caused by rotation of the polishing platen 4 and also with a
function of the depth of the pad grooves 42 increasing stepwisely,
the slurry 16 and shavings produced by the polishing pad 40 can
easily be discharged. When the slurry 16 and the shavings are
easily discharged, a new slurry 16 supplied from the slurry nozzle
14 is supplied to the polishing surface of the wafer 12, thereby
making it possible to prevent generation of micro scratches. Note
that, in addition to the pad grooves 42 formed in the polishing pad
40, holes may further be formed therein.
Third Embodiment
[0046] FIG. 8 is a top view of a polishing pad 50 according to a
third embodiment of the present invention. The polishing pad 50 is
made of a synthetic resin such as polyurethane. Pad grooves 52 are
arranged so as to extend radially from a center of the polishing
pad 50. The pad grooves 52 are formed by mechanical machining.
Further, the pad grooves 52 has a U-shaped section (not shown). The
pad grooves section may be inclined surface as shown in FIGS. 6A
and 6B but U-shaped section.
[0047] FIG. 9 is a sectional view of the polishing pad 50 according
to the third embodiment of the present invention. FIG. 9 is a
sectional view taken along the line C-C' of FIG. 8. From a center
50c of the polishing pad 50 toward an outer edge of the polishing
pad 50, a pad groove base portion 52a forms an inclined surface.
Note that, the polishing pad 50 is composed of two layers, that is,
an upper layer polishing pad 50a and a lower layer polishing pad
50b. The pad grooves 52 are formed in the upper layer polishing pad
50a.
[0048] As described above, the polishing pad 50 has a structure in
which a depth of the pad groove 52 increases from the center 50c
toward the outer edge. Accordingly, with a centrifugal force caused
by rotation of the polishing platen 4 and also with a function of
the pad groove 52 having the depth increasing, the slurry 16 and
shavings produced by the polishing pad 50 can easily be discharged.
When the slurry 16 and the shavings are easily discharged, a new
slurry 16 supplied from the slurry nozzle 14 is supplied to the
polishing surface of the wafer 12, thereby making it possible to
prevent generation of micro scratches. Note that, in addition to
the pad grooves 52 formed in the polishing pad 50, holes may
further be formed therein.
Fourth Embodiment
[0049] FIG. 10 is a top view of a polishing pad 60 according to a
fourth embodiment of the present invention. The polishing pad 60 is
formed of a synthetic resin such as polyurethane. Pad grooves 62
are arranged so as to extend spirally from a center of the
polishing pad 60. The pad grooves 62 are formed by mechanical
machining. Further, the pad groove 62 has a U-shaped section (not
shown). However, as shown in FIG. 6, pad groove walls may form
inclined surfaces.
[0050] FIG. 11 is a sectional view of the polishing pad 60
according to the fourth embodiment of the present invention. FIG.
11 is a sectional view taken along the line D-D' of FIG. 10. From a
center 60c of the polishing pad 60 toward an outer edge of the
polishing pad 60, a pad groove base portion 62a forms an inclined
surface. Note that, the polishing pad 60 is composed of two layers,
that is, an upper layer polishing pad 60a and a lower layer
polishing pad 60b. The pad grooves 62 are formed in the upper layer
polishing pad 60a.
[0051] As described above, the polishing pad 60 has a structure in
which from the center 60c to the outer edge, a depth of the pad
groove 62 increases. Accordingly, with a centrifugal force caused
by the rotation of the polishing platen 4 and also with a function
of the pad groove 62 having the depth increasing, the slurry 16 and
shavings produced by the polishing pad 60 are easily discharged.
When the slurry 16 and the shavings are easily discharged, a new
slurry 16 supplied by the slurry nozzle 14 is supplied to the
polishing surface of the wafer 12, thereby making it possible to
prevent generation of micro scratches. Note that, in addition to
the pad grooves 62 formed in the polishing pad 60, holes may
further be formed therein.
[0052] In the above description, the first to fourth embodiments
are described. However, the first to fourth embodiments may be
employed in any combination.
* * * * *