U.S. patent application number 11/889505 was filed with the patent office on 2007-12-27 for cmp-apparatus retainer ring and manufacturing method thereof, and cmp apparatus.
This patent application is currently assigned to Nippon Seimitsu Denshi Co., Ltd.. Invention is credited to Tsutomu Ichinoshime.
Application Number | 20070298693 11/889505 |
Document ID | / |
Family ID | 37214492 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070298693 |
Kind Code |
A1 |
Ichinoshime; Tsutomu |
December 27, 2007 |
CMP-apparatus retainer ring and manufacturing method thereof, and
CMP apparatus
Abstract
A retainer ring is provided which is capable of, effectively in
practice, restraining the time taken for a break-in polish to the
minimum. This retainer ring 8: is disposed inside of a holding head
4 in a CMP apparatus 1 which polishes a wafer W chemically and
mechanically; has a ring shape so as to surround the periphery of
the wafer W; presses a polish surface 3a of a polish pad 3; is made
of an engineering plastic material such as PPS; and has a pressure
surface 8a for pressing the polish surface 3a of the polish pad 3
whose surface roughness is a center-line average roughness (Ra) of
0.01 .mu.m or below.
Inventors: |
Ichinoshime; Tsutomu;
(Yokohama-shi, JP) |
Correspondence
Address: |
ARENT FOX LLP
1050 CONNECTICUT AVENUE, N.W.
SUITE 400
WASHINGTON
DC
20036
US
|
Assignee: |
Nippon Seimitsu Denshi Co.,
Ltd.
|
Family ID: |
37214492 |
Appl. No.: |
11/889505 |
Filed: |
August 14, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP05/07067 |
Apr 12, 2005 |
|
|
|
11889505 |
Aug 14, 2007 |
|
|
|
60924744 |
May 30, 2007 |
|
|
|
Current U.S.
Class: |
451/285 ;
257/E21.23 |
Current CPC
Class: |
H01L 21/30625 20130101;
B24B 37/32 20130101 |
Class at
Publication: |
451/285 |
International
Class: |
B24B 29/00 20060101
B24B029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2005 |
JP |
2005-114076 |
Claims
1. A CMP-apparatus retainer ring which, in a CMP apparatus that
includes a polish pad disposed on a base and a holding head holding
a wafer and pressing the wafer against the polish pad and that
polishes the wafer chemically and mechanically: is provided inside
of the holding head; has a ring shape so as to surround the
periphery of the wafer; and presses the polish surface of the
polish pad, characterized in that: the retainer ring is made of an
engineering plastic material; and the surface roughness of a
pressure surface for pressing the polish surface of the polish pad
is a center-line average roughness of 0.01 .mu.m or below.
2. The CMP-apparatus retainer ring according to claim 1,
characterized in that: in the back surface of the retainer ring
located at the back surface of the pressure surface, a portion to
be held is formed; and the pressure surface is polished.
3. A CMP-apparatus retainer-ring manufacturing method for, in a CMP
apparatus that includes a polish pad disposed on a base and a
holding head holding a wafer and pressing the wafer against the
polish pad and that polishes the wafer chemically and mechanically,
manufacturing an engineering-plastic retainer ring which is
provided inside of the holding head, has a ring shape so as to
surround the periphery of the wafer and presses the polish surface
of the polish pad, characterized by including the steps of: working
a shaped surface other than a pressure surface for pressing the
polish surface of the polish pad so that the shaped surface has a
predetermined measurement; holding the retainer ring without
applying an external-circumference pressure and an
internal-circumference pressure to the retainer ring; and machining
the pressure surface in this state, and polishing the pressure
surface until the surface roughness thereof becomes a center-line
average roughness of 0.01 .mu.m or below.
4. The CMP-apparatus retainer-ring manufacturing method according
to claim 3, characterized in that: the polish pad disposed on the
base, a pressing means for rotating the retainer ring and pressing
the pressure surface thereof against the polish pad and a slurry
supplying means for supplying slurry to the polish pad are
provided; and the polishing is conducted by a polishing apparatus
which regulates a pressure and a rotational speed given by the
pressing means and a slurry supply given by the slurry supplying
means.
5. The CMP-apparatus retainer-ring manufacturing method according
to claim 4, characterized in that before the polishing is
conducted, break-in working is conducted by attaching a break-in
retainer ring to the polishing apparatus.
6. The CMP-apparatus retainer-ring manufacturing method according
to any one of claims 3 to 5, characterized in that the machining
and the polishing are conducted with holding only the side of the
back surface of the retainer ring located at the back surface of
the pressure surface.
7. The CMP-apparatus retainer-ring manufacturing method according
to claim 6, characterized in that: a portion to be held is formed
in the back surface of the retainer ring; the retainer ring is held
by a machining jig which includes a holding portion that holds this
portion to be held; and the machining is conducted in this
state.
8. The CMP-apparatus retainer-ring manufacturing method according
to claim 7, characterized in that: the machining jig holding the
retainer ring is supported by a polishing jig which supports the
side of the back surface of the machining jig located at the back
surface of the holding portion; and the polishing is conducted in
this state.
9. A CMP-apparatus retainer-ring machining jig which is the
machining jig used in the CMP-apparatus retainer-ring manufacturing
method according to claim 7, characterized in that, the machining
jig: has a flat-board shape; and in an attachment surface which
comes into surface contact with the back surface of the retainer
ring, includes the holding portion which holds the portion to be
held that is formed in the back surface of the retainer ring.
10. A CMP-apparatus retainer-ring polishing jig which is the
polishing jig used in the CMP-apparatus retainer-ring manufacturing
method according to claim 8, characterized in that, the polishing
jig: has a flat-board shape; and includes a concave supporting
portion which houses the side of the back surface of the machining
jig located at the back surface of the attachment surface, is
fitted to the peripheral surface of the machining jig and supports
the back surface of the machining jig.
11. A CMP apparatus which: includes a polish pad disposed on a base
and a holding head that holds a wafer and presses the wafer against
the polish pad, this holding head having a retainer ring which has
a ring shape so as to surround the periphery of the wafer and
presses the polish surface of the polish pad; and polishes the
wafer chemically and mechanically, characterized in that: the
retainer ring is made of an engineering plastic material; and the
surface roughness of a pressure surface of the retainer ring for
pressing the polish surface of the polish pad is set at a
center-line average roughness of 0.01 .mu.m or below.
Description
TECHNICAL FIELD
[0001] The present invention relates to a CMP (or chemical
mechanical polishing) apparatus which polishes a wafer chemically
and mechanically. Particularly, it relates to a retainer ring which
is provided on (attached to) the inside of a holding head of the
CMP Apparatus and surrounds the periphery of the wafer.
BACKGROUND ART
[0002] As a semiconductor device has more highly integrated and has
performed better, its measurements in the horizontal directions (on
the plane) have shortened and the structure in the vertical
directions has been fined down and multi-layered. In order to
realize such a fine and multi-layered structure, a semiconductor
substrate (such as a silicon substrate) needs to have a high
flatness (evenness). Hence, the flatness has to be heightened at
the stage of a wafer, and in response to this demand, a CMP
Apparatus is used.
[0003] This CMP Apparatus is configured by, for example: a rotary
base; a polish pad disposed on this base; and a holding head which
holds a wafer and presses it onto the polish pad; a slurry supply
nozzle; and the like. The holding head is formed by: a retainer
ring which surrounds the periphery of the wafer; for example, an
elastic film which pushes (presses) the upper surface of the wafer;
an air chamber which is enclosed with this elastic film, the
retainer ring and a head body; an air supply path which supplies
air for pressurization into this air chamber. The retainer ring
surrounds the periphery of the wafer and prevents the wafer from
popping out. It also presses the polish surface of the polish pad,
and flattens and fines down (suits) the polish surface of the
polish pad which polishes the wafer. Hence, the retainer ring's
pressure surface (surface for pressing the polish pad) needs to
have a low surface roughness.
[0004] On the other hand, since such a retainer ring presses the
polish pad, its pressure surface itself is supposed to be polished
and worn off by the polish pad. This requires that the retainer
ring be regularly replaced. However, if the retainer ring's
pressure surface is rough, then a predetermined polishing
performance, or a desirable flatness of a wafer, cannot be
obtained. In the case where the retainer ring has been exchanged,
therefore, before a product wafer (a wafer which is manufactured as
a product) begins to be polished, a break-in (preparatory) polish
needs to be given using a newly-attached retainer ring.
Specifically, this new retainer ring is attached to the holding
head of the CMP Apparatus and dozens of dummy wafers (break-in
wafers) are polished. After it is ascertained that a suitable
polishing performance has been obtained, for the first time, a
polish is given to the product wafer. This break-in polishing
requires a great deal of time and labor, thus lowering the
production availability of wafers.
[0005] Taking this into account, in order to shorten the time taken
for the break-in polishing, a retainer ring whose pressure surface
is subjected to surface working (machining) so that it has a
predetermined smoothness is known (e.g., refer to Patent Document
1). Specifically, in this retainer ring, its pressure surface is
designed to have a surface roughness of 0.8 .mu.m or below at the
maximum height (Rmax). This makes it possible to dispense with such
break-in polishing. [0006] Patent Document 1: Japanese Patent
Laid-Open No. 2002-126995 specification
DISCLOSURE OF THE INVENTION
[0006] Problems to be Solved by the Invention
[0007] However, an extremely high flatness is necessary for a
wafer, and such a high flatness cannot be satisfied with the
retainer ring given in Patent Document 1 described above.
Specifically, the pressure surface's surface roughness is some 0.8
.mu.m at the maximum height, and thus, the polish pad's polish
surface cannot be flattened and fined down desirably (up to a high
level). Even if a wafer is polished with this polish pad, an
extremely high flatness cannot be obtained. This requires, in
practice, a break-in polish which takes a long time equivalent to
the time taken conventionally. Besides, in terms of the surface
roughness described in Patent Document 1, the smallest value is 0.6
.mu.m at the maximum height. If the surface roughness is such a
roughness level, a long-time break-in polish has to be given in the
same way as the case of 0.8 .mu.m. Incidentally, according to
Patent Document 1, the pressure surface's surface roughness is set
to 0.8 .mu.m or below at the maximum height, so that a polishing
rate and the polishing rate's uniformity within the surface can be
enhanced. However, the polishing rate only expresses how fast
(mm/min) a wafer can be polished, and thus, it is not supposed to
indicate that a wafer can be polished so as to have a high
flatness.
[0008] In addition, the flatness of a wafer polished by the CMP
Apparatus depends upon the material of a retainer ring and its
pressure surface's surface roughness. In other words, if the
retainer ring's material and its pressure surface's surface
roughness are specified, that makes it possible to polish a wafer
to a high flatness. However, in Patent Document 1, no mention is
made of a retainer ring's material. Hence, it is unclear whether a
retainer ring made of a specific material can enjoy the advantage
in that its pressure surface is set to have a surface roughness of
0.8 .mu.m or below at the maximum height so that break-in polishing
can be dispensed with.
[0009] As described so far, according to the retainer ring and
disclosure contents given in Patent Document 1, not only break-in
polishing cannot be saved, but also effectively in practice, the
time taken for such break-in polishing cannot be kept down to the
minimum.
[0010] Therefore, it is an object of the present invention to
provide a retainer ring and a manufacturing method thereof which
are capable of, effectively in practice, restraining the time taken
for a break-in polish to the minimum.
Means for Solving the Problems
[0011] In order to attain the above described object, a
CMP-apparatus retainer ring according to claim 1 which, in a CMP
apparatus that includes a polish pad disposed on a base and a
holding head holding a wafer and pressing the wafer against the
polish pad and that polishes the wafer chemically and mechanically:
is provided inside of the holding head; has a ring shape so as to
surround the periphery of the wafer; and presses the polish surface
of the polish pad, characterized in that: the retainer ring is made
of an engineering plastic material; and the surface roughness of a
pressure surface for pressing the polish surface of the polish pad
is a center-line average roughness (arithmetic average roughness)
of 0.01 .mu.m or below.
[0012] A CMP-apparatus retainer ring according to claim 2,
characterized in that, in the CMP-apparatus retainer ring according
to claim 1: in the back surface of the retainer ring located at the
back surface of the pressure surface, a portion to be held is
formed; and the pressure surface is polished.
[0013] A CMP-apparatus retainer-ring manufacturing method according
to claim 3 for, in a CMP apparatus that includes a polish pad
disposed on a base and a holding head holding a wafer and pressing
the wafer against the polish pad and that polishes the wafer
chemically and mechanically, manufacturing an engineering-plastic
retainer ring which is provided inside of the holding head, has a
ring shape so as to surround the periphery of the wafer and presses
the polish surface of the polish pad, characterized by including
the steps of: working a shaped surface other than a pressure
surface for pressing the polish surface of the polish pad so that
the shaped surface has a predetermined measurement; holding the
retainer ring without applying an external-circumference pressure
and an internal-circumference pressure to the retainer ring; and
machining the pressure surface in this state, and polishing the
pressure surface until the surface roughness thereof becomes a
center-line average roughness of 0.01 .mu.m or below.
[0014] A CMP-apparatus retainer-ring manufacturing method according
to claim 4, characterized in that, in the CMP-apparatus
retainer-ring manufacturing method according to claim 3: the polish
pad disposed on the base, a pressing means for rotating the
retainer ring and pressing the pressure surface thereof against the
polish pad and a slurry supplying means for supplying slurry to the
polish pad are provided; and the polishing is conducted by a
polishing apparatus which regulates a pressure and a rotational
speed given by the pressing means and a slurry supply given by the
slurry supplying means.
[0015] A CMP-apparatus retainer-ring manufacturing method according
to claim 5, characterized in that, in the CMP-apparatus
retainer-ring manufacturing method according to claim 4, before the
polishing is conducted, break-in working is conducted by attaching
a break-in retainer ring to the polishing apparatus.
[0016] A CMP-apparatus retainer-ring manufacturing method according
to claim 6, characterized in that, in the CMP-apparatus
retainer-ring manufacturing method according to any one of claims 3
to 5, the machining and the polishing are conducted with holding
only the side of the back surface of the retainer ring located at
the back surface of the pressure surface.
[0017] A CMP-apparatus retainer-ring manufacturing method according
to claim 7, characterized in that, in the CMP-apparatus
retainer-ring manufacturing method according to claim 6: a portion
to be held is formed in the back surface of the retainer ring; the
retainer ring is held by a machining jig which includes a holding
portion that holds this portion to be held; and the machining is
conducted in this state.
[0018] A CMP-apparatus retainer-ring manufacturing method according
to claim 8, characterized in that, in the CMP-apparatus
retainer-ring manufacturing method according to claim 7: the
machining jig holding the retainer ring is supported by a polishing
jig which supports the side of the back surface of the machining
jig located at the back surface of the holding portion; and the
polishing is conducted in this state.
[0019] A CMP-apparatus retainer-ring machining jig according to
claim 9 which is the machining jig used in the CMP-apparatus
retainer-ring manufacturing method according to claim 7,
characterized in that the machining jig: has a flat-board shape;
and in an attachment surface which comes into surface contact with
the back surface of the retainer ring, includes the holding portion
which holds the portion to be held that is formed in the back
surface of the retainer ring.
[0020] A CMP-apparatus retainer-ring machining jig according to
claim 10 which is the polishing jig used in the CMP-apparatus
retainer-ring manufacturing method according to claim 8,
characterized in that the polishing jig: has a flat-board shape;
and includes a concave supporting portion which houses the side of
the back surface of the machining jig located at the back surface
of the attachment surface, is fitted to the peripheral surface of
the machining jig and supports the back surface of the machining
jig.
[0021] A CMP apparatus according to claim 11 which: includes a
polish pad disposed on a base and a holding head that holds a wafer
and presses the wafer against the polish pad, this holding head
having a retainer ring which has a ring shape so as to surround the
periphery of the wafer and presses the polish surface of the polish
pad; and polishes the wafer chemically and mechanically,
characterized in that: the retainer ring is made of an engineering
plastic material; and the surface roughness of a pressure surface
of the retainer ring for pressing the polish surface of the polish
pad is set at a center-line average roughness of 0.01 .mu.m or
below.
Advantages of the Invention
[0022] In the CMP-apparatus retainer ring according to claim 1,
which is made of engineering plastics, its pressure surface's
surface roughness is a center-line average roughness of 0.01 .mu.m
or below. Therefore, in practice, the time taken for a break-in
polish can be effectively restrained to the minimum. Specifically,
in this retainer ring, the pressure surface's surface roughness
indicates an extremely small value of 0.01 .mu.m or below. Thereby,
from immediately after the retainer ring has been attached to the
holding head of the CMP apparatus, the polish pad's polish surface
is flattened and fined down desirably (up to a high level) with the
retainer ring's pressure surface. This helps obtain a suitable
polishing performance, in other words, polish a wafer to an
extremely high flatness, without giving any break-in polish or only
by giving a short-time (minimal) break-in polish. As a result, the
time and labor taken for such a break-in polish can be kept down to
the minimum. Effectively in practice, this makes it possible to
enhance the production availability of wafers. Besides, the time
taken for a break-in polish comes to the minimum, so that polish
scrap produced through the break-in polish can be reduced,
scratches on a wafer by such polish scrap are less likely, or
impurities are less likely to adhere to a wafer. Consequently, the
production quality of a wafer becomes higher and more stable, thus
decreasing the number of defective products and enhancing the
productivity further.
[0023] In the CMP-apparatus retainer ring according to claim 2, the
portion to be held of the back surface is held, so that the
retainer ring can be held without deforming the pressure surface.
Therefore, polishing is conducted with held in this state, thus
helping make the pressure surface's surface roughness extremely
fine.
[0024] In the CMP-apparatus retainer-ring manufacturing method
according to claim 3, after the shaped surface other than the
pressure surface is wrought so as to have a predetermined
measurement, the pressure surface is machined and polished
(lapped). Therefore, the pressure surface which has undergone
machining or the like is not deformed in the following working.
Furthermore, it is subjected to machining or the like in a state
where the retainer ring is held without given an
external-circumference pressure and an internal-circumference
pressure. This prevents such a hold from deforming the pressure
surface. Moreover, through machining (such as cutting and
grinding), the pressure surface's flatness and surface roughness
reach a specific measurement (level), and thereafter, polishing is
conducted. This helps conduct such polishing desirably. As a
result, the pressure surface can be finished off so as to have a
high flatness and an extremely-low surface roughness.
[0025] In the CMP-apparatus retainer-ring manufacturing method
according to claim 4, in accordance with the material or size of
the retainer ring, the kind of slurry (abrasive) or the like, the
pressure or the rotational speed by the pressing means, or the
slurry supply, is regulated. Therefore, the retainer ring's
pressure surface can be polished to a high flatness and an
extremely-low surface roughness.
[0026] In the CMP-apparatus retainer-ring manufacturing method
according to claim 5, break-in working is conducted, so that the
polish pad (such as a cloth) of the polishing apparatus is suited
(flattened and fined down) and stabilized. Therefore, in the
following polishing, the retainer ring's pressure surface can be
wrought well (so as to have a high flatness and an extremely-low
surface roughness).
[0027] In the CMP-apparatus retainer-ring manufacturing method
according to claim 6, the machining and the polishing are conducted
with holding only the side of the back surface of the retainer
ring. Therefore, this hold can be prevented from deforming the
pressure surface, thus working the pressure surface desirably.
[0028] In the CMP-apparatus retainer-ring manufacturing method
according to claim 7, the portion to be held which is formed in the
back surface of the retainer ring is held, and in this state, the
pressure surface is machined. Therefore, the retainer ring's hold
can be prevented from deforming the pressure surface, thus
machining the pressure surface desirably.
[0029] In the CMP-apparatus retainer-ring manufacturing method
according to claim 8, the side of the back surface of the machining
jig which holds the retainer ring is supported by the polishing
jig. Therefore, this support can be prevented from deforming the
retainer ring's pressure surface. Besides, the polishing can be
conducted in a state where the retainer ring is held on the
machining jig. In other words, the machining and the polishing can
be continuously conducted without removing the retainer ring from
the machining jig. This helps maintain the machining jig's holding
accuracy and holding stability. As a result, the pressure surface
can be properly polished.
[0030] In the CMP-apparatus retainer-ring machining jig according
to claim 9, the portion to be held which is formed in the back
surface of the retainer ring is held by the machining jig.
Therefore, this hold can be prevented from deforming the retainer
ring's pressure surface. In addition, the back surface of the
retainer ring comes into surface contact with the attachment
surface of the machining jig, and in this state, the retainer ring
is held on the machining jig. Consequently, at the time of
machining, the retainer ring's pressure surface becomes more
stable. As a result, the pressure surface can be appropriately
machined.
[0031] In the CMP-apparatus retainer-ring polishing jig according
to claim 10, the side of the back surface of the machining jig
which holds the retainer ring is supported by the polishing jig.
Therefore, this support can be prevented from deforming the
retainer ring's pressure surface. Besides, the polishing can be
conducted in a state where the retainer ring is held on the
machining jig. Besides, the supporting portion is fitted to the
peripheral surface of the machining jig, so that the machining jig
(the retainer ring) can be prevented from shifting sideward.
Simultaneously, it supports the back surface of the machining jig
(the back surface of the retainer ring), so that a working force
applied to the retainer ring's pressure surface is properly
supported. This helps stabilize the pressure surface at the time of
polishing. As a result, the pressure surface can be suitably
polished.
[0032] In the CMP apparatus according to claim 11, in terms of the
retainer ring, its pressure surface's surface roughness is set to a
center-line average roughness of 0.01 .mu.m or below. Therefore, in
practice, the time taken for a break-in polish can be effectively
restrained to the minimum. Specifically, in this retainer ring, the
pressure surface's surface roughness indicates an extremely small
value of 0.01 .mu.m or below. Thereby, from immediately after the
retainer ring has been attached to the holding head, the polish
pad's polish surface is flattened and fined down desirably with the
pressure surface. This helps obtain a suitable polishing
performance, without giving any break-in polish or only by giving a
short-time break-in polish. As a result, the time and labor taken
for such a break-in polish can be kept down to the minimum.
Effectively in practice, this makes it possible to enhance the
production availability of wafers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a front view of a CMP apparatus according to an
embodiment of the present invention, showing a schematic
configuration thereof.
[0034] FIG. 2 is a schematic sectional view of a holding head of
the CMP apparatus according to the embodiment of the present
invention.
[0035] FIGS. 3(a) and 3(b) are a plan view and a side sectional
view, respectively, of a CMP-apparatus retainer ring according to
the embodiment of the present invention.
[0036] FIG. 4 is a table, showing a manufacturing process flow for
the CMP-apparatus retainer ring according to the embodiment of the
present invention.
[0037] FIG. 5 is a front view (partial sectional view) of a
machining jig for working ahead of polishing (machining) the
CMP-apparatus retainer ring according to the embodiment of the
present invention.
[0038] FIG. 6 is a sectional view of a polishing jig for polishing
the CMP-apparatus retainer ring according to the embodiment of the
present invention.
[0039] FIG. 7 is a table, showing a measurement result or the like
of the surface roughness of a pressure surface of the CMP-apparatus
retainer ring according to the embodiment of the present
invention.
[0040] FIG. 8 is an illustration, showing measurement points for
the surface roughness of the pressure surface of the CMP-apparatus
retainer ring according to the embodiment of the present
invention.
[0041] FIG. 9 is a table, showing a measurement result of the
surface roughness of the pressure surface of the CMP-apparatus
retainer ring according to the embodiment of the present
invention.
BEST MODE FOR IMPLEMENTING THE INVENTION
[0042] Hereinafter, a CMP-apparatus retainer ring according to an
embodiment of the present invention will be described with
reference to the attached drawings.
[0043] FIG. 1 is a front view of a CMP apparatus 1 according to the
embodiment of the present invention, showing a schematic
configuration thereof. This CMP apparatus 1 has a configuration
equivalent to a CMP apparatus which is widely used in general,
apart from a retainer ring 8 (described later). Herein, a detailed
description is omitted. It includes: a base 2 which can be rotated;
a polish pad 3 (such as a cloth) which is disposed on this base 2;
a holding head 4; a slurry supply nozzle 5 (a slurry supplying
means); and a dresser 6 (a dressing means). It polishes a wafer W
chemically and mechanically.
[0044] The holding head 4 holds the wafer W and presses its surface
W1 to be polished against the polish pad 3. It is designed to move
on the polish pad 3 while rotating. This holding head 4 is, as
shown in FIG. 2, provided with: a head body 7; the retainer ring 8
which is disposed under this head body 7; and an elastic film 9
which is located inside of this retainer ring 8 and presses an
upper surface W2 of the wafer W. Then, an air chamber 10 is
enclosed with the head body 7, the retainer ring 8 and the elastic
film 9, and air for pressurization is supplied into this air
chamber 10. Via the elastic film 9, the holding head 4 presses the
wafer W onto the polish pad 3.
[0045] The retainer ring 8 surrounds the periphery of the wafer W
and prevents the wafer W from popping out of the holding head 4. It
also presses a polish surface 3a of the polish pad 3, and flattens
and fines down (suits) the polish surface 3a (the part which comes
into surface contact with the polished surface W1 of the wafer W)
of the polish pad 3 which polishes the wafer W. Specifically, the
polish surface 3a of the polish pad 3 becomes so as that its
flatness is low and the surface roughness is rough with using
slurry 5a (abrasive). Hence, the retainer ring 8 enhances this
polish surface 3a's flatness and lowers the surface roughness.
[0046] In consideration of chemical resistance, mechanical
properties or the like, this retainer ring 8 is made of a PPS
(polyphenylene sulfide, engineering plastic) material. It has, as
shown in FIG. 3, a ring shape. In a pressure surface 8a for
pressing the polish surface 3a of the polish pad 3, a plurality of
slits 8b are formed which are each shaped like a groove for
allowing polish scrap to escape (discharge). In a back surface 8c
of the retainer ring 8 located at the back surface of the pressure
surface 8a, a plurality of screw inserts 8d (portions to be held)
each of which has a female thread 8e are inserted. In other words,
such a screw insert 8d is substantially cylindrical, and a male
thread is formed in its external-circumference part and the female
thread 8e is formed in its internal-circumference part. In
addition, the pressure surface 8a's surface roughness is set (the
surface is polished) to a center-line average roughness (arithmetic
average roughness, Ra) of 0.01 .mu.m or below.
[0047] Next, the method of manufacturing the retainer ring 8 having
such a configuration will be described based on a process flow
shown in FIG. 4.
[0048] First, in a first process, a PPS blank is roughly cut into a
shape near the final shape and measurements. Next, tapping
(female-thread formation) is conducted on the side of the back
surface 8c (Process 2), and into this tap, the screw insert 8d is
screwed (inserted, Process 3). Sequentially, cutting is conducted
so that the internal diameter becomes a predetermined measurement
(Process 4). Thereafter, cutting is conducted on the sides of the
pressure surface 8a and the back surface 8c so that the retainer
ring 8's height (thickness) becomes a predetermined measurement
(Process 5). Afterward, cutting is conducted so that the external
diameter becomes a predetermined measurement (Process 6) and
milling is conducted so that the slits 8b are formed on the side of
the pressure surface 8a (Process 7). Then, burrs produced in such
working are removed (Process 8) and cutting is conducted again on
the side of the back surface 8c (Process 9). At this time, in the
cutting, it is shallowly cut so that the flatness becomes higher on
the side of the back surface 8c. Through Process 1 to Process 9
described above, the shaped surfaces other than the pressure
surface 8a are wrought so as to have the predetermined
measurements.
[0049] Sequentially, using such a machining jig 11 as shown in FIG.
5, the pressure surface 8a of the retainer ring 8 is wrought ahead
of a polish (machined) (Process 10). This machining jig 11 is made
of stainless steel and is shaped like a disk (a flat board). Its
external diameter is almost equal to the external diameter of the
retainer ring 8. Besides, bolt holes 11c are formed in the same
positions (at the same pitch) as the screw inserts 8d of the
retainer ring 8. Through such a bolt hole 11c, a bolt 12 (a holding
portion) is inserted from the side of a back surface 11b to the
side of an attachment surface 11a. With this attachment surface 11a
of the machining jig 11, the back surface 8c of the retainer ring 8
comes into surface contact, and the bolt 12 is tightened on the
screw inserts 8d. Thereby, without applying an
external-circumference pressure and an internal-circumference
pressure to the retainer ring 8, the retainer ring 8 is held by the
machining jig 11. Next, the peripheral part of the machining jig 11
is grasped by the chuck of a lathe, and the pressure surface 8a of
the retainer ring 8 is subjected to surface cutting in the lathe.
At this time, it is shallowly cut and the rotation is slowed in the
lathe so that the pressure surface 8a has a high flatness and a low
surface roughness. Incidentally, in this embodiment, the pressure
surface 8a is cut by the lathe, but in accordance with the retainer
ring 8's material, hardness or the like, some other machining such
as grinding may also be conducted.
[0050] After this, without detaching the retainer ring 8 from the
machining jig 11, using such a polishing jig 13 as shown in FIG. 6,
the pressure surface 8a of the retainer ring 8 is polished (Process
11). This polishing jig 13 is made of poly-vinyl chloride and is
shaped like a disk (a flat board). In its central part, a concave
supporting portion 13a is formed. This supporting portion 13a's
internal diameter is almost equal to the machining jig 11's
external diameter, so that it can be fitted exactly to the
machining jig 11's peripheral surface. In this supporting portion
13a, the side of the back surface 11b of the machining jig 11 is
housed (inserted). Thereby, the back surface 11b of the machining
jig 11 is supported on a bottom surface 13b of the supporting
portion 13a. On this bottom surface 13b, a protective cloth 14 is
provided which protects the machining jig 11. This polishing jig 13
supports the machining jig 11 holding the retainer ring 8, and in
this state, the pressure surface 8a is polished.
[0051] This polishing is conducted by a polishing apparatus (a
lapping machine, a polishing machine) which has a configuration
equivalent to the above described CMP apparatus 1. Specifically,
this polishing apparatus includes: a polish pad (equivalent to the
polish pad 3) which is disposed on a base; a pressing means
(equivalent to the holding head 4) which presses the pressure
surface 8a against the polish pad while rotating the retainer ring
8; and a slurry supplying means (equivalent to the slurry supply
nozzle 5) which supplies slurry to the polish pad. It is designed
to regulate a pressure and a rotational speed given by the pressing
means, a slurry supply given by the slurry supplying means, and the
like. In accordance with the retainer ring 8's material quality
(such as hardness) or size, the kind of slurry (abrasive) or the
like, polishing conditions are regulated such as the pressure or
the rotational speed by the pressing means and the slurry supply.
Then, the pressure surface 8a of the retainer ring 8 is polished.
As those polishing conditions, an example is specifically given
below.
[0052] Slurry 5a; CO (diluent is a cerium system) and the particle
diameter is 2 .mu.m [0053] Supply of slurry; 500-1000 ml/min.
[0054] Temperature of a base; 24-26.quadrature. (the cooling-water
temperature of a base) [0055] Pressure by the pressing means; 0.2
kgf/cm.sup.2 [0056] Rotational speed by the pressing means; 50
rpm
[0057] In this polishing apparatus, before the retainer ring 8 is
polished, break-in working is conducted by attaching a break-in
retainer ring (a dummy retainer ring) thereto. Through this
break-in working, the polish pad of the polishing apparatus is
suited (flattened and fined down) and stabilized. After this
break-in working, the retainer ring 8 is polished on the above
described polishing conditions until the pressure surface 8a's
surface roughness becomes a center-line average roughness of 0.01
.mu.m or below.
[0058] After this polishing, polish scrap is cleared away by means
of an air blow, and each part is measured (Process 12). Then, the
retainer ring 8 which has the predetermined measurements and
surface roughness undergoes an ultrasonic cleaning (Process 13).
This puts an end to the manufacturing process.
[0059] Next, in the retainer ring 8 which has been produced through
the above described manufacturing process, a measurement result of
the pressure surface 8a's surface roughness will be described. FIG.
7 shows this measurement result, and the measurement is conducted
in the following measuring instrument and under measurement
conditions. Herein, measurement points A, B are positions shown in
FIG. 8.
[0060] Measuring instrument; Surftest SV-3000S4 (a contact-point
type surface-roughness measuring instrument) by Mitsutoyo
Corporation [0061] Standard; OLDMIX [0062] Evaluation curve type; R
[0063] Reference length; 0.8 mm [0064] Interval function; 5 [0065]
Ac (a cut-off value); 0.8 mm [0066] Filter type; Gaussian [0067]
Evaluation length; 4.0 mm [0068] Entrance length; 0.4 mm [0069]
Exit length; 0.3985 mm [0070] Smooth connection; Off [0071] Average
line correction at the time of a parameter calculation; Off
[0072] In FIG. 7, the values of Sample 1 are a measurement result
of this retainer ring 8, and at both the measurement points A, B,
the surface roughness is a center-line average roughness (Ra) of
0.01 .mu.m. In terms of the maximum height (Ry), it is 0.080 .mu.m
at the measurement point A and 0.108 .mu.m at the measurement point
B. Hence, in this retainer ring 8, the pressure surface 8a's
surface roughness is far lower than the retainer ring's surface
roughness (some 0.8 .mu.m at the maximum height) given in Patent
Document 1 described above. On the other hand, when the pressure
surface of the same retainer ring (with the same material, the same
measurements) as this retainer ring 8 is polished (lapped) by hand,
a measurement result of its surface roughness is given by the
values of Sample 2 in FIG. 7. In respect of the center-line average
roughness, it is 0.220 .mu.m at the measurement point A and 0.201
.mu.m at the measurement point B. In respect of the maximum height,
it is 1.776 .mu.m at the measurement point A and 1.923 .mu.m at the
measurement point B. Incidentally, in the case of a metal product
(metal working), if its surface roughness is a center-line average
roughness of 0.01 .mu.m or below, this surface is said to be
mirror-finished. In this retainer ring 8, the pressure surface 8a's
surface roughness is 0.01 .mu.m or below, and thus, it is supposed
to be a mirror-finished surface in a metal product. In FIG. 7, a
surface roughness "Rq" is a square average square-root roughness;
"Rz" is a ten-point average roughness; "Rc" is an average
concave-convex height; "Rp" is a maximum peak height; "Rv" is a
maximum valley depth; and "Rt" is a maximum section height.
[0073] As described above, in this retainer ring 8, the pressure
surface 8a's surface roughness is a center-line average roughness
of 0.01 .mu.m or below. It is extremely low, and thus, when this
retainer ring 8 is attached to a CMP apparatus, in practice, the
time taken for a break-in polish can be effectively restrained to
the minimum. Specifically, because the pressure surface 8a's
surface roughness is extremely low, from immediately after this
retainer ring 8 has been attached to the holding head 4 of the CMP
apparatus 1, the polish pad 3's polish surface 3a is flattened and
fined down desirably (up to a high level) with the pressure surface
8a. This helps obtain a suitable polishing performance, in other
words, polish the polished surface W1 of the wafer W to an
extremely high flatness, without giving any break-in polish or only
by giving a short-time (minimal) break-in polish. As a result, the
time and labor taken for such a break-in polish can be kept down to
the minimum. Effectively in practice, this makes it possible to
enhance the production availability of the wafer W.
[0074] For example, in a conventional retainer ring whose pressure
surface is rough, before the product wafer W (a wafer which is
manufactured as a product) begins to be polished, external
preparation and a break-in polish have to be given. Specifically,
in the external preparation, this retainer ring is roughly cut for
approximately ten minutes by a dedicated polishing apparatus (a
polishing machine). Thereafter, it is polished and finished for
about fifteen minutes by another dedicated polishing apparatus and
is cleaned for some twenty minutes with ultrasonic waves. Then, in
a break-in polish, the retainer ring is attached to the holding
head 4, and twenty or more dummy wafers (break-in wafers) are
polished. Then, it has to be ascertained that a suitable polishing
performance has been obtained. In contrast, in the retainer ring 8
according to the present invention, the pressure surface 8a's
surface roughness is extremely low, and thus, there is no need to
conduct such external preparation. Besides, even though it depends
somewhat upon the CMP apparatus l's working accuracy (processing
precision), the polish pad 3's type or conditions (such as a
flatness) or the like, without giving any break-in polish or only
by giving a break-in polish for several minutes immediately after
this retainer ring 8 has been attached to the holding head 4, the
polished surface W1 of the wafer W can be polished to an extremely
high flatness. Incidentally, the conventional retainer ring's
pressure surface is cut, for example, only by a lathe. Hence, its
surface roughness is a center-line average roughness of around 3.0
.mu.m.
[0075] Furthermore, the time taken for a break-in polish is
minimized. Therefore, polish scrap produced through the break-in
polish is reduced, scratches on the wafer W by such polish scrap
are less likely, or impurities are less likely to adhere to it.
Consequently, the production quality of the wafer W becomes higher
and more stable, thus decreasing the number of defective products
and enhancing the productivity further.
[0076] Herein, in this retainer ring 8, the pressure surface 8a's
surface roughness is a center-line average roughness of 0.01 .mu.m
or below. It is extremely low because of such a manufacturing
process as described earlier. Specifically, first, through Process
1 to Process 9, the shaped surfaces other than the pressure surface
8a are wrought so as to have the predetermined measurements.
Thereafter, the pressure surface 8a is wrought ahead of a polish
(Process 10) and is polished (Process 11). This prevents the
pressure surface 8a after wrought from undergoing some change in
its shape. In other words, if another shaped surface is wrought
after the pressure surface 8a has been wrought so as to have a
predetermined measurement or the like, the pressure surface 8a may
be deformed to change its measurements or the like. In this
manufacturing process, however, such a deformation can be
evaded.
[0077] Moreover, with holding the retainer ring 8 without applying
any external-circumference pressure and internal-circumference
pressure to the retainer ring 8, it is wrought ahead of a polish
and is polished. Thereby, some hold can be prevented from deforming
the pressure surface 8a. Specifically, in the working ahead of
polishing (pre-polish working, Process 10), the bolt 12 of the
machining jig 11 is tightened on the screw inserts 8d of the
retainer ring 8, so that the retainer ring 8 can be held on the
machining jig 11. Therefore, the pressure surface 8a will not be
deformed by this hold. Besides, the back surface 8c of the retainer
ring 8 is supported on the attachment surface 11a of the machining
jig 11. This stabilizes the pressure surface 8a of the retainer
ring 8 while being wrought ahead of a polish. As a result, the
pressure surface 8a is wrought ahead of a polish desirably (up to a
high flatness and a low surface roughness). Then, through this
working ahead of polishing, the pressure surface 8a's flatness and
surface roughness reach a specific measurement (level), and
thereafter, polishing is conducted. This makes it possible to
finish off (polish) the pressure surface 8a so that it has a high
flatness and an extremely-low surface roughness.
[0078] In addition, in the following polishing (Process 11), the
side of the back surface 11b of the machining jig 11 holding the
retainer ring 8 is supported on the polishing jig 13. Therefore,
the pressure surface 8a of the retainer ring 8 will not be deformed
by this hold. Besides, the supporting portion 13a of the polishing
jig 13 is fitted to the machining jig 11's peripheral surface. This
helps prevent the machining jig 11 (the retainer ring 8) from
slipping laterally. Besides, the back surface 11b of the machining
jig 11 (the back surface 8c of the retainer ring 8) is supported on
the bottom surface 13b of the supporting portion 13a. Thereby, a
working force (a polishing force) applied to the retainer ring 8's
pressure surface 8a is appropriately supported. This helps
stabilize the pressure surface 8a at the time of polishing.
Further, the polishing can be conducted in a state where the
retainer ring 8 is held on the machining jig 11. In other words,
the working ahead of polishing and the polishing can be
continuously conducted without removing the retainer ring 8 from
the machining jig 11. This helps maintain the machining jig 11's
holding accuracy and holding stability. As a result, the pressure
surface 8a can be polished up to a high flatness and an
extremely-low surface roughness.
[0079] Furthermore, in the polishing, as described earlier, in
accordance with the material or size of the retainer ring 8, the
kind of the slurry 5a or the like, the pressure or the rotational
speed by the pressing means, the slurry supply or the like is
regulated. Therefore, the retainer ring 8's pressure surface 8a can
be polished to a high flatness and an extremely-low surface
roughness. Besides, before the retainer ring 8 is polished,
break-in working is conducted using a break-in retainer ring.
Through this break-in working, the polish pad of the polishing
apparatus is suited (flattened and fined down) and stabilized.
After the break-in working, the retainer ring 8's pressure surface
8a is polished, and thus, the pressure surface 8a can be wrought
well (so as to have a high flatness and an extremely-low surface
roughness).
[0080] As a result, in the retainer ring 8, the pressure surface
8a's surface roughness can be polished (finished off) up to an
extremely low value, or a center-line average roughness of 0.01
.mu.m or below.
[0081] Incidentally, in this embodiment, the retainer ring 8 is
made of PPS, but it may also be another kind of engineering
plastics, such as PEEK (polyether etherketone), PET (polyethylene
terephthalate), POM (polyacetals) and PI (polyimide). In the same
way as the retainer ring 8 according to this embodiment, its
pressure surface's surface roughness can be set to a center-line
average roughness of 0.01 .mu.m or below. For example, a retainer
ring is made of a PEEK material, is subjected to the same
manufacturing process as described earlier, and its pressure
surface's surface roughness is measured. This measurement result is
shown in Sample 3 of FIG. 7. Consequently, at both the measurement
points A, B, the surface roughness is a center-line average
roughness of 0.009 .mu.m. In terms of the maximum height, it is
0.076 .mu.m at the measurement point A and is 0.074 .mu.m at the
measurement point B. Hence, in the retainer ring 8 made of a PEEK
material, its surface roughness is slightly lower than the retainer
ring 8 according to this embodiment which is made of a PPS
material. Because the hardness of a PEEK material is a little
higher (harder) than that of a PPS material. The values of Sample 4
in FIG. 7 indicate a measurement result of the PEEK-made retainer
ring's surface roughness when the pressure surface is polished by
hand.
[0082] Moreover, if a pressure surface is polished using slurry
whose particle diameter is smaller, the pressure surface's surface
roughness becomes lower. For example, in a retainer ring made of a
PPS material, its pressure surface is polished with slurry which
has a particle diameter of 1.2 .mu.m. In this case, as shown in
FIG. 9, a lower surface roughness is obtained. For example, in
terms of the center-line average roughness, it is 0.004 .mu.m at
the measurement point A and is 0.005 .mu.m at the measurement point
B. In terms of the maximum height, it is 0.049 .mu.m at the
measurement point A and is 0.051 .mu.m at the measurement point B.
Hence, if the particle diameter of slurry is set to be smaller in
accordance with the material or hardness of a retainer ring, its
pressure surface's surface roughness can be reduced further. In
FIG. 9, measurement points C, D, E are measurement positions shown
in FIG. 8.
INDUSTRIAL APPLICABILITY
[0083] As describe so far, a CMP-apparatus retainer ring according
to the present invention is extremely useful as a retainer ring
which is capable of restraining the time taken for a break-in
polish to the minimum, as well as enhancing and stabilizing the
production quality of a wafer.
* * * * *