U.S. patent application number 15/052540 was filed with the patent office on 2016-08-25 for retainer ring, substrate holding apparatus, and polishing apparatus, and retainer ring maintenance method.
The applicant listed for this patent is EBARA CORPORATION. Invention is credited to Makoto FUKUSHIMA, Keisuke NAMIKI, Hozumi YASUDA.
Application Number | 20160243670 15/052540 |
Document ID | / |
Family ID | 56690200 |
Filed Date | 2016-08-25 |
United States Patent
Application |
20160243670 |
Kind Code |
A1 |
FUKUSHIMA; Makoto ; et
al. |
August 25, 2016 |
RETAINER RING, SUBSTRATE HOLDING APPARATUS, AND POLISHING
APPARATUS, AND RETAINER RING MAINTENANCE METHOD
Abstract
According to one embodiment, a retainer ring for retaining a
substrate to be polished, includes: an inside ring arranged to
enclose the substrate; and an outside ring arranged outside the
inside ring, abrasion-resistant of the outside ring being higher
than abrasion-resistant of the inside ring, wherein the inside ring
having a thickness in a radial direction in a range from a minimum
of 0.05 mm to a maximum of 5 mm.
Inventors: |
FUKUSHIMA; Makoto; (Tokyo,
JP) ; YASUDA; Hozumi; (Tokyo, JP) ; NAMIKI;
Keisuke; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EBARA CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
56690200 |
Appl. No.: |
15/052540 |
Filed: |
February 24, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24B 37/32 20130101 |
International
Class: |
B24B 37/32 20060101
B24B037/32 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2015 |
JP |
2015-033668 |
Claims
1. A retainer ring for retaining a substrate to be polished, the
retainer ring comprising: an inside ring arranged to enclose the
substrate; and an outside ring arranged outside the inside ring,
abrasion-resistant of the outside ring being higher than
abrasion-resistant of the inside ring, wherein the inside ring
having a thickness in a radial direction in a range from a minimum
of 0.05 mm to a maximum of 5 mm.
2. The retainer ring according to claim 1, wherein a convex portion
toward the polishing pad is formed on a lower surface of the
outside ring.
3. The retainer ring according to claim 2, wherein a distance
between a tip of the convex portion and an end of the outside ring
with no convex portion is below 30 .mu.m.
4. The retainer ring according to claim 1, wherein the inside ring
is detachably attached to the outside ring.
5. The retainer ring according to claim 1, wherein a material of
the inside ring includes one or more of PPS, PEEK, PTFE, PP, PET,
polycarbonate, and polyacetal.
6. The retainer ring according to claim 1, wherein a material of
the outside ring includes one or more of ceramic materials and
metallic materials.
7. The retainer ring according to claim 1, wherein surface
roughness of a lower surface of the outside ring is a maximum of Ra
1.6 .mu.m.
8. The retainer ring according to claim 1, wherein Rockwell M
hardness of the inside ring is in a range from a minimum of 70 to a
maximum of 120.
9. The retainer ring according to claim 1, wherein on a lower
surface of the inside ring and a lower surface of the outside ring,
a plurality of grooves extending in radial directions and
communicating the inside ring and the outside ring are formed.
10. A substrate holding apparatus comprising: a top ring body for
holding a substrate; and the retainer ring according to claim 1,
the retainer ring being arranged to enclose the substrate held by
the top ring body.
11. A polishing apparatus comprising: a polishing pad; and the
substrate holding apparatus according to claim 10, the substrate
holding apparatus pressing the substrate onto the polishing
pad.
12. A method for maintaining a retainer ring for retaining a
substrate to be polished, the retainer ring comprising: an inside
ring arranged to enclose the substrate; and an outside ring
arranged outside the inside ring, abrasion-resistant of the outside
ring being higher than abrasion-resistant of the inside ring,
wherein the inside ring having a thickness in a radial direction in
a range from a minimum of 0.05 mm to a maximum of 5 mm, and wherein
the inside ring is detachably attached to the outside ring, the
method comprising: removing the inside ring from the outside ring;
and fixing a new inside ring onto the outside ring.
13. A retainer ring for retaining a substrate to be polished, the
retainer ring comprising: an inside ring arranged to enclose the
substrate; and an outside ring arranged outside the inside ring,
the outside ring comprising a lower ring and an upper ring, wherein
abrasion-resistant of the lower ring is higher than
abrasion-resistant of the inside ring, and toughness of the upper
ring is higher than toughness of the lower ring.
14. The retainer ring according to claim 13, wherein a convex
portion toward the polishing pad is formed on a lower surface of
the outside ring.
15. The retainer ring according to claim 14, wherein a distance
between a tip of the convex portion and an end of the outside ring
with no convex portion is below 30 .mu.m.
16. The retainer ring according to claim 13, wherein the inside
ring is detachably attached to the outside ring.
17. The retainer ring according to claim 13, wherein a material of
the inside ring includes one or more of PPS, PEEK, PTFE, PP, PET,
polycarbonate, and polyacetal.
18. The retainer ring according to claim 13, wherein a material of
the outside ring includes one or more of ceramic materials and
metallic materials.
19. The retainer ring according to claim 19, wherein surface
roughness of a lower surface of the outside ring is a maximum of Ra
1.6 .mu.m.
20. The retainer ring according to claim 10, wherein Rockwell M
hardness of the inside ring is in a range from a minimum of 70 to a
maximum of 120.
21. The retainer ring according to claim 11, wherein on a lower
surface of the inside ring and a lower surface of the outside ring,
a plurality of grooves extending in radial directions and
communicating the inside ring and the outside ring are formed.
22. A retainer ring for retaining a substrate to be polished, the
retainer ring comprising: an inside ring arranged to enclose the
substrate; an outside ring arranged outside the inside ring,
abrasion-resistant of the outside ring being higher than
abrasion-resistant of the inside ring and the outside ring being
harder than the inside ring; wherein the outside ring and the
inside ring are individually, vertically movable each other, and
the outside ring is either contact-less with the polishing pad, or
is pressed onto the polishing pad with a force smaller than another
force pressing the inside ring onto the polishing pad.
23. The retainer ring according to claim 22, wherein a material of
the inside ring includes one or more of PPS, PEEK, PTFE, PP, PET,
polycarbonate, and polyacetal.
24. The retainer ring according to claim 22, wherein a material of
the outside ring includes one or more of ceramic materials and
metallic materials.
25. The retainer ring according to claim 22, wherein surface
roughness of a lower surface of the outside ring is a maximum of Ra
1.6 .mu.m.
26. The retainer ring according to claim 22, wherein Rockwell M
hardness of the inside ring is in a range from a minimum of 70 to a
maximum of 120.
27. The retainer ring according to claim 22, wherein on a lower
surface of the inside ring and a lower surface of the outside ring,
a plurality of grooves extending in radial directions and
communicating the inside ring and the outside ring are formed.
28. A substrate holding apparatus comprising: a top ring body
holding a substrate; and the retainer ring according to claim 22,
the retainer ring being arranged to enclose the substrate held by
the top ring body.
29. A polishing apparatus comprising: a polishing pad; and the
substrate holding apparatus according to claim 28, the substrate
holding apparatus pressing the substrate onto the polishing pad.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Japanese Priority
Patent Application JP 2015-33668 filed on Feb. 24, 2015, the entire
contents of which are incorporated herein by reference.
FIELD
[0002] The present technology relates to substrate holding
apparatuses that hold substrates, such as wafers, and in
particular, relates to a substrate holding apparatus used for
polishing a surface of a substrate by pressing the substrate onto a
polishing tool, such as a polishing pad. The present technology
further relates to a polishing apparatus that uses such a substrate
holding apparatus. The present technology still further relates to
a retainer ring used in the above described substrate holding
apparatus.
BACKGROUND AND SUMMARY
[0003] A polishing apparatus for polishing a surface of a wafer is
widely used in a process for manufacturing semiconductor devices.
Such a kind of the polishing apparatus includes a polishing table
supporting a polishing pad having a polishing face, a substrate
holding apparatus holding a wafer referred to as a top ring or a
polishing head, and a polishing liquid supply nozzle supplying a
polishing liquid onto the polishing face.
[0004] The polishing apparatus polishes a wafer as described below.
While allowing the polishing table to rotate together with the
polishing pad, the apparatus supplies the polishing liquid onto the
polishing face from the polishing liquid supply nozzle. The
substrate holding apparatus holds and rotates the wafer at an axial
center of the wafer. In this state, the substrate holding apparatus
presses a surface of the wafer onto the polishing face of the
polishing pad to allow the surface of the wafer to come into
sliding contact with the polishing face while the polishing liquid
is being supplied. The surface of the wafer is evenly polished
through a mechanical action of abrasive grain contained in the
polishing liquid and a chemical action of the polishing liquid. The
described polishing apparatus is also referred to as a chemical
mechanical polishing (CMP) apparatus.
[0005] While polishing the wafer is underway, the surface of the
wafer comes into sliding contact with the polishing pad, causing a
friction force on the wafer. To prevent the wafer from coming off
the substrate holding apparatus due to the friction force occurred
while the wafer is polished, the substrate holding apparatus
includes a retainer ring. The retainer ring is arranged to enclose
the wafer to press the polishing pad outside the wafer.
[0006] A wafer polishing rate (or, removal rate) could change
depending on polishing conditions such as a load of the wafer
against the polishing pad, a load of the retainer ring, a rotating
speed of the polishing table and the wafer, and a type of the
polishing liquid. To obtain the same level of polishing finish when
polishing a plurality of wafers successively, such polishing
conditions are normally maintained at a constant level. However, a
polishing profile at an edge of each of the plurality of wafers
could change gradually as polishing of the plurality of wafers
proceeds even though the polishing conditions are kept unchanged.
Specifically, the polishing rate at the edge increases as many
wafers are polished.
[0007] A reason of such increase of the polishing rate is assumed
to be that the retainer ring changes in shape. FIG. 19 is a
schematic view illustrating a retainer ring while a wafer is
polished. As shown in FIG. 19, a retainer ring 200 wears while
polishing the wafer W is underway, because the retainer ring 200 is
pressed against a polishing face 201a of a polishing pad 201. Inner
and outer peripheral surfaces of the retainer ring 200 particularly
wear, resulting in the rounded inner and outer peripheral surfaces.
When the inner peripheral surface of the retainer ring 200 wears as
shown in FIG. 19, a force of the retainer ring 200 to press a pad
area near an edge of the wafer W lowers, increasing the polishing
rate at the edge.
[0008] Therefore, there is a need for substrate holding apparatuses
that are able to stabilize a substrate polishing rate even when
successively polishing a plurality of substrates (wafers, for
example). There is a further need for polishing apparatuses that
use such substrate holding apparatuses. There is a still further
need for retainer rings used in such substrate holding apparatuses,
as well as a retainer ring maintenance method.
[0009] According to one embodiment, a retainer ring for retaining a
substrate to be polished, includes: an inside ring arranged to
enclose the substrate; and an outside ring arranged outside the
inside ring, abrasion-resistant of the outside ring being higher
than abrasion-resistant of the inside ring, wherein the inside ring
having a thickness in a radial direction in a range from a minimum
of 0.05 mm to a maximum of 5 mm.
[0010] According to another embodiment, a retainer ring for
retaining a substrate to be polished, includes: an inside ring
arranged to enclose the substrate; and an outside ring arranged
outside the inside ring, the outside ring comprising a lower ring
and an upper ring, wherein abrasion-resistant of the lower ring is
higher than abrasion-resistant of the inside ring, and toughness of
the upper ring is higher than toughness the lower ring.
[0011] According to another embodiment, a retainer ring for
retaining a substrate to be polished, includes: an inside ring
arranged to enclose the substrate; an outside ring arranged outside
the inside ring, abrasion-resistant of the outside ring being
higher than abrasion-resistant of the inside ring and the outside
ring being harder than the inside ring; wherein the outside ring
and the inside ring are individually, vertically movable each
other, and the outside ring is either contact-less with the
polishing pad, or is pressed onto the polishing pad with a force
smaller than another force pressing the inside ring onto the
polishing pad.
[0012] According to another embodiment, a substrate holding
apparatus includes: a top ring body for holding a substrate; and
the above retainer ring, the retainer ring being arranged to
enclose the substrate held by the top ring body.
[0013] According to another embodiment, a polishing apparatus
includes: a polishing pad; and the substrate holding apparatus
according to claim 10, the substrate holding apparatus pressing the
substrate onto the polishing pad.
[0014] According to another embodiment, a method for maintaining
the above retainer ring, includes: removing the inside ring from
the outside ring; and fixing a new inside ring onto the outside
ring.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a schematic view illustrating a polishing
apparatus including a substrate holding apparatus according to an
embodiment.
[0016] FIG. 2 is a view illustrating a detailed configuration of
the polishing apparatus.
[0017] FIG. 3A is a cross-sectional view illustrating the top ring
1.
[0018] FIGS. 3B and 3C are enlarged cross-sectional views
illustrating different phases of an outer periphery of a drive ring
81.
[0019] FIG. 4 is a plain view illustrating the drive ring 81 and
the coupling member 75.
[0020] FIG. 5 is a view illustrating the spherical bearing 85.
[0021] FIG. 6A is a drawing illustrating vertical movement of the
coupling member 75 relative to the spherical bearing 85.
[0022] FIGS. 6B and 6C are drawings illustrating tilt movement of
the coupling member 75 together with the inner ring 101.
[0023] FIG. 7 is an enlarged cross-sectional view illustrating
another configuration example of a spherical bearing 85.
[0024] FIG. 8A is a drawing illustrating vertical movement of the
coupling member 75 relative to the spherical bearing 85.
[0025] FIGS. 8B and 8C are drawings illustrating tilt movement of
the coupling member 75 together with the intermediate ring 91.
[0026] FIG. 9 is an enlarged partial cross-sectional view of the
retainer ring 40.
[0027] FIG. 10 is a view schematically illustrating a change in a
surface shape of the retainer ring 40 shown in FIG. 9 after used
for a long period of time.
[0028] FIGS. 11A to 11D are graphs showing measurement results of
cross sectional shapes of a typical retainer ring after used for a
long period of time.
[0029] FIGS. 12 to 14 are graphs showing measurement results of
shapes of lower surfaces of typical retainer rings after used for a
long period of time.
[0030] FIGS. 15A to 15F are enlarged views of various outside rings
40b.
[0031] FIG. 16 is a cross-sectional view illustrating an example
method for fixing an inside ring 40a and an outside ring 40b.
[0032] FIG. 17 is an enlarged partial cross-sectional view of a
retainer ring 40', a modified example of the retainer ring 40 shown
in FIG. 9.
[0033] FIG. 18 is a bottom view of a retainer ring 40.
[0034] FIG. 19 is a schematic view illustrating a retainer ring
while a wafer is polished.
DETAILED DESCRIPTION OF NON-LIMITING EXAMPLE EMBODIMENTS
[0035] A detailed description will hereinafter be given with
reference to the drawings.
[0036] According to one embodiment, a retainer ring for retaining a
substrate to be polished, includes: an inside ring arranged to
enclose the substrate; and an outside ring arranged outside the
inside ring, abrasion-resistant of the outside ring being higher
than abrasion-resistant of the inside ring, wherein the inside ring
having a thickness in a radial direction in a range from a minimum
of 0.05 mm to a maximum of 5 mm.
[0037] Since the outside ring is highly abrasion-resistant, and an
appropriate distance is set between an inner peripheral surface of
the inside ring and a convex portion, it is possible to maintain a
load acting point of the retainer ring near an edge of the
substrate, stabilizing a polishing rate.
[0038] According to another embodiment, a retainer ring for
retaining a substrate to be polished, includes: an inside ring
arranged to enclose the substrate; and an outside ring arranged
outside the inside ring, the outside ring comprising a lower ring
and an upper ring, wherein abrasion-resistant of the lower ring is
higher than abrasion-resistant of the inside ring, and toughness of
the upper ring is higher than toughness of the lower ring.
[0039] Since the outside ring is highly abrasion-resistant, it is
possible to maintain a load acting point of the retainer ring near
an edge of the substrate, stabilizing a polishing rate. Also, the
tough upper ring allows the retainer ring to firmly be attached
with another component.
[0040] It is preferable that a convex portion toward the polishing
pad is formed on a lower surface of the outside ring.
[0041] By such a manner, the load acting point is prevented from
being moved away from a substrate in a radial direction.
[0042] It is more preferable that a distance between a tip of the
convex portion and an end of the outside ring with no convex
portion is below 30 .mu.m.
[0043] Therefore, a substrate polishing rate can be stabilized.
[0044] It is preferable that the inside ring is detachably attached
to the outside ring.
[0045] Therefore, only the inside ring can be replaced when the
inside ring is worn, while continuously using a highly
abrasion-resistant outside ring.
[0046] According to another embodiment, a retainer ring for
retaining a substrate to be polished, includes: an inside ring
arranged to enclose the substrate; an outside ring arranged outside
the inside ring, abrasion-resistant of the outside ring being
higher than abrasion-resistant of the inside ring and the outside
ring being harder than the inside ring; wherein the outside ring
and the inside ring are individually, vertically movable each
other, and the outside ring is either contact-less with the
polishing pad, or is pressed onto the polishing pad with a force
smaller than another force pressing the inside ring onto the
polishing pad.
[0047] Since the outside ring is highly abrasion-resistant, it is
possible to maintain a load acting point of the retainer ring near
an edge of the substrate, stabilizing a polishing rate.
[0048] A material of the inside ring may include one or more of
PPS, PEEK, PTFE, PP, PET, polycarbonate, and polyacetal. A material
of the outside ring may include one or more of ceramic materials
and metallic materials.
[0049] Preferably, surface roughness of a lower surface of the
outside ring is a maximum of Ra 1.6 .mu.m, and Rockwell M hardness
of the inside ring is in a range from a minimum of 70 to a maximum
of 120.
[0050] Preferably, on a lower surface of the inside ring and a
lower surface of the outside ring, a plurality of grooves extending
in radial directions and communicating the inside ring and the
outside ring are formed.
[0051] According to another embodiment, a substrate holding
apparatus includes: a top ring body holding a substrate; and the
above retainer ring, the retainer ring being arranged to enclose
the substrate held by the top ring body.
[0052] According to another embodiment, a polishing apparatus
includes: a polishing pad; and the substrate holding apparatus
according to claim 31, the substrate holding apparatus pressing the
substrate onto the polishing pad.
[0053] According to another embodiment, a method for maintaining
the above retainer ring, includes: removing the inside ring from
the outside ring; and fixing a new inside ring onto the outside
ring.
[0054] FIG. 1 is a schematic view illustrating a polishing
apparatus including a substrate holding apparatus according to an
embodiment. As shown in FIG. 1, the polishing apparatus includes a
top ring (substrate holding apparatus) 1 holding and rotating a
wafer (substrate) W, a polishing table 3 supporting a polishing pad
2, a polishing liquid supply nozzle 5 supplying polishing liquid
(slurry) onto the polishing pad 2, and a film thickness sensor 7
retrieving film thickness signals that changes depending a film
thickness of the wafer W. The film thickness sensor 7 is arranged
inside the polishing table 3, retrieving the film thickness signals
at a plurality of areas including a center of the wafer W each time
the polishing table 3 rotates once. The film thickness sensor 7 may
be, for example, an optical sensor or an eddy current sensor.
[0055] The top ring 1 is configured to hold the wafer W by vacuum
contact onto the lower surface of the wafer W. The top ring 1 and
the polishing table 3 rotate in the same direction indicated by an
arrow, during which the top ring 1 presses the wafer W against a
polishing face 2a of the polishing pad 2. The polishing liquid
supply nozzle 5 supplies the polishing liquid onto the polishing
pad 2, during which the wafer W comes into sliding contact with the
polishing pad 2 for polishing. While the wafer W is polished, the
film thickness sensor 7 rotates together with the polishing table 3
across a surface of the wafer W, as indicated by symbol A, to
retrieve the film thickness signals. The film thickness signals are
index values directly or indirectly indicate film thicknesses, and
the film thickness signals change as the film thickness of the
wafer W decreases. The film thickness sensor 7 is connected to a
polishing controller 9, to which the film thickness signals is
sent. The polishing controller 9 stops polishing the wafer W upon
the film thickness signals indicate that the film thickness of the
wafer W reaches a predetermined target value.
[0056] FIG. 2 is a view illustrating a detailed configuration of
the polishing apparatus. The polishing table 3 is coupled, via a
table shaft 3a, to a motor 13 arranged under the polishing table 3
so that the polishing table 3 can rotate around the table shaft 3a.
The polishing pad 2 is pasted on an upper surface of the polishing
table 3 so that an upper surface of the polishing pad 2 configures
the polishing face 2a polishing the wafer W. The motor 13 rotates
the polishing table 3, resulting in that the polishing face 2a
moves relative to the top ring 1. The motor 13 therefore configures
a polishing face moving mechanism that horizontally moves the
polishing face 2a.
[0057] The top ring 1 is connected to a top ring shaft 11 that
vertically moves by a vertical movement mechanism 27 relative to a
top ring head 16. By vertical movement of the top ring shaft 11,
the top ring 1 raises or lowers entirely relative to the top ring
head 16 for positioning. An upper end of the top ring shaft 11 is
attached with a rotary joint 25.
[0058] The vertical movement mechanism 27, which vertically moves
the top ring shaft 11 and the top ring 1, includes a bridge 28
rotatably supporting the top ring shaft 11 via a bearing 26, a ball
screw 32 attached to the bridge 28, a support table 29 supported by
a support column 30, and a servomotor 38 arranged on the support
table 29. The support table 29 supporting the servomotor 38 is
fixed to the top ring head 16 via the support column 30.
[0059] The ball screw 32 includes a screw shaft 32a coupled to the
servomotor 38 and a nut 32b into which the screw shaft 32a is
screwed. The top ring shaft 11 vertically moves together with the
bridge 28. When the servomotor 38 is driven, accordingly the bridge
28 is vertically moved via the ball screw 32, and thus the top ring
shaft 11 and the top ring 1 are vertically moved.
[0060] The top ring shaft 11 is coupled to a rotating cylinder 12
via a key (not shown). An outer periphery of the rotating cylinder
12 is equipped with a timing pulley 14. A top ring motor 18 is
fixed to the top ring head 16, and the above described timing
pulley 14 is connected, via a timing belt 19, to a timing pulley 20
attached to the top ring motor 18. Therefore, rotary-driving the
top ring motor 18 allows the rotating cylinder 12 and the top ring
shaft 11 to rotate together, via the timing pulley 20, the timing
belt 19, and the timing pulley 14, and thus allows the top ring 1
to rotate at an axial center. The top ring motor 18, the timing
pulley 20, the timing belt 19, and the timing pulley 14 configure a
rotation mechanism rotating the top ring 1 at the axial center. The
top ring head 16 is supported by a top ring head shaft 21 rotatably
supported by a frame (not shown).
[0061] The top ring 1 can hold the substrate, such as the wafer W,
at the lower surface. The top ring head 16 is configured in a
rotatable manner around the top ring head shaft 21, moving the top
ring 1 holding the wafer W at the lower surface, through rotation
of the top ring head 16, from a wafer W--receiving position to
above the polishing table 3. The top ring 1 is then lowered to
press the wafer W against the polishing face 2a of the polishing
pad 2. At this time, the top ring 1 and the polishing table 3 are
rotated separately, and the polishing liquid is supplied from the
polishing liquid supply nozzle 5 arranged above the polishing table
3 onto the polishing pad 2. In this manner, the wafer W is come
into sliding contact with the polishing face 2a of the polishing
pad 2 to polish the surface of the wafer W.
[0062] Next, the top ring 1 configuring the substrate holding
apparatus will be described. FIG. 3A is a cross-sectional view
illustrating the top ring 1. As shown in FIG. 3A, the top ring 1
includes a top ring body 10 holding and pressing the wafer W
against the polishing face 2a, and a retainer ring 40 arranged to
enclose the wafer W. The top ring body 10 and the retainer ring 40
are configured to rotate together through rotation of the top ring
shaft 11. The retainer ring 40 is configured in a vertically
movable manner relative to the top ring body 10. The present
embodiment has an object to stabilize a polishing rate by
appropriately configuring the retainer ring 40, the retainer ring
40 being described in detail in and after FIG. 9.
[0063] The top ring body 10 includes a circular flange 41, a spacer
42 attached at a lower surface of the flange 41, and a carrier 43
attached at a lower surface of the spacer 42. The flange 41 is
coupled to the top ring shaft 11. The carrier 43 is coupled, via
the spacer 42, to the flange 41 so that the flange 41, the spacer
42, and the carrier 43 rotate together and vertically move. The top
ring body 10 configured with the flange 41, the spacer 42, and the
carrier 43 is molded of a resin such as engineer plastic (PEEK, for
example). The flange 41 may be molded of metal such as SUS or
aluminum.
[0064] Under a lower surface of the carrier 43, an elastic film 45
that comes into contact with a back of the wafer W is attached. A
lower surface of the elastic film 45 configures a substrate holding
face 45a. The elastic film 45 has a plurality of annular partition
walls 45b forming, between the elastic film 45 and the top ring
body 10, four pressure chambers, i.e. a center chamber 50, a ripple
chamber 51, an outer chamber 52, and an edge chamber 53. The four
pressure chambers 50 to 53 are connected, via the rotary joint 25,
to a pressure regulator 65 that supplies a pressurized fluid. The
pressure regulator 65 can separately adjust pressure in the four
pressure chambers 50 to 53. The pressure regulator 65 can further
form negative pressure in the four pressure chambers 50 to 53.
[0065] The elastic film 45 has a through hole (not shown) at a
position corresponding to the ripple chamber 51 or the outer
chamber 52 so that, by forming negative pressure in the through
hole, the top ring 1 can hold the wafer W at the substrate holding
face 45a. The elastic film 45 is molded of a highly strong and
durable rubber material, such as ethylene propylene rubber (EPDM),
polyurethane rubber, or silicone rubber. The center chamber 50, the
ripple chamber 51, the outer chamber 52, and the edge chamber 53
are also connected to an atmosphere open mechanism (not shown) so
that the center chamber 50, the ripple chamber 51, the outer
chamber 52, and the edge chamber 53 are atmospherically open.
[0066] The retainer ring 40 is arranged to enclose the carrier 43
and the elastic film 45 of the top ring body 10. The retainer ring
40 is a ring-shaped member for coming into contact with the
polishing face 2a of the polishing pad 2. The retainer ring 40 is
arranged to enclose an outer periphery edge of the wafer W to hold
the wafer W so that the wafer W does not come off the top ring 1
while the wafer W is polished.
[0067] FIGS. 3B and 3C are enlarged cross-sectional views
illustrating different phases of an outer periphery of a drive ring
81. As shown in FIGS. 3B and 3C, an upper surface of the retainer
ring 40 is positioned to the drive ring 81 by a plurality of
reinforcing pins 82, and is fixed with a plurality of screws 83.
The plurality of reinforcing pins 82 and the plurality of screws 83
are respectively arranged circumferentially and evenly. A top of
the drive ring 81 is coupled to an annular retainer ring pressing
mechanism 60 applying a load downwardly, evenly, and entirely to
the upper surface of the retainer ring 40 via the drive ring 81 to
press a lower surface of the retainer ring 40 against the polishing
face 2a of the polishing pad 2.
[0068] The retainer ring pressing mechanism 60 includes an annular
piston 61 fixed to the top of the drive ring 81 and an annular
rolling diaphragm 62 connected to an upper surface of the piston
61. A retainer ring pressure chamber 63 is formed inside the
rolling diaphragm 62. The retainer ring pressure chamber 63 is
connected to the pressure regulator 65 via the rotary joint 25.
[0069] When the pressurized fluid (pressurized air, for example) is
supplied from the pressure regulator 65 to the retainer ring
pressure chamber 63, the rolling diaphragm 62 presses down the
piston 61, and then the piston 61 presses down, via the drive ring
81, the retainer ring 40 entirely. The retainer ring pressing
mechanism 60 presses in this manner the lower surface of the
retainer ring 40 against the polishing face 2a of the polishing pad
2. In addition to this, the pressure regulator 65 can form negative
pressure inside the retainer ring pressure chamber 63 to raise the
retainer ring 40 entirely. The retainer ring pressure chamber 63 is
also connected to the atmosphere open mechanism (not shown) so as
to be atmospherically open.
[0070] The drive ring 81 is detachably coupled to the retainer ring
pressing mechanism 60. More specifically, the piston 61 is molded
of a magnetic material, such as metal, and the top of the drive
ring 81 is arranged with a plurality of magnets 70. The plurality
of magnets 70 attracts the piston 61 to secure the drive ring 81 to
the piston 61. The magnetic material used to mold the piston 61 may
be, for example, corrosion-resistant magnetic stainless steel. In
contrast, the drive ring 81 may be molded of a magnetic material,
and the piston 61 may be arranged with a plurality of magnets.
[0071] The retainer ring 40 is coupled to a spherical bearing 85
via the drive ring 81 and a coupling member 75. The spherical
bearing 85 is arranged inside the retainer ring 40 inwardly in a
radial direction. FIG. 4 is a plain view illustrating the drive
ring 81 and the coupling member 75. As shown in FIG. 4, the
coupling member 75 includes a shaft 76 arranged at a center of the
top ring body 10, a hub 77 fixed to the shaft 76, and a plurality
of spokes 78 radially extending from the hub 77.
[0072] One end of the spokes 78 is fixed to the hub 77, and the
other end of the spokes 78 is fixed to the drive ring 81. The hub
77 and the plurality of spokes 78 are integrally formed together
with the drive ring 81. The carrier 43 is fixed with a plurality of
pairs of drive pins 80, 80. Each pair of the drive pins 80, 80 is
arranged on both sides of each of the spokes 78 to transmit
rotation of the carrier 43 to the drive ring 81 and the retainer
ring 40 via the drive pins 80, 80 so that the top ring body 10 and
the retainer ring 40 can rotate together.
[0073] As shown in FIG. 3A, the shaft 76 extends longitudinally
inside the spherical bearing 85. As shown in FIG. 4, in the carrier
43 is formed a plurality of radial grooves 43a accommodating the
plurality of spokes 78 so that each of the spokes 78 are
longitudinally movable in each of the grooves 43a. The shaft 76 of
the coupling member 75 is longitudinally and movably supported by
the spherical bearing 85 arranged at the center of the top ring
body 10. According to the above described configuration, the
coupling member 75 is longitudinally movable together with the
drive ring 81 and the retainer ring 40 coupled to the coupling
member 75 relative to the top ring body 10. The drive ring 81 and
the retainer ring 40 are further tiltably and movably supported by
the spherical bearing 85.
[0074] FIG. 5 is a view illustrating the spherical bearing 85. The
shaft 76 is fixed to the hub 77 with a plurality of screws 79. The
shaft 76 is formed with a longitudinally extending through hole 88.
The through hole 88 acts as an air vent hole when the shaft 76
longitudinally moves relative to the spherical bearing 85, allowing
the retainer ring 40 to longitudinally and smoothly move relative
to the top ring body 10.
[0075] The spherical bearing 85 includes an annular inner ring 101
and an outer ring 102 slidably supporting an outer peripheral
surface of the inner ring 101. The inner ring 101 is coupled, via
the coupling member 75, the drive ring 81 and the retainer ring 40.
The outer ring 102 is fixed to a supporting member 103 fixed to the
carrier 43. The supporting member 103 is arranged inside a recessed
portion 43b of the carrier 43.
[0076] The outer peripheral surface of the inner ring 101 has a
spherical shape where a top and a bottom are cut into flat
surfaces, and a center (fulcrum) O of the spherical shape positions
at a center of the inner ring 101. An inner peripheral surface of
the outer ring 102 is configured with a recessed surface along with
the outer peripheral surface of the inner ring 101 so that the
outer ring 102 slidably supports the inner ring 101. The inner ring
101 is therefore tiltably and omni-directionally) (360.degree.)
movable relative to the outer ring 102.
[0077] An inner peripheral surface of the inner ring 101 is
configured with a through hole 101a into which the shaft 76 is
inserted. The shaft 76 is only longitudinally movable relative to
the inner ring 101. The retainer ring 40 coupled to the shaft 76
therefore cannot move laterally, and thus a lateral (horizontal)
position of the retainer ring 40 is secured by the spherical
bearing 85. The spherical bearing 85 functions as a supporting
mechanism to restrict lateral movement of the retainer ring 40
(i.e. securing the horizontal position of the retainer ring 40),
while receiving a lateral force (a force in an outward radial
direction of the wafer) applied from the wafer W against the
retainer ring 40 due to friction between the wafer W and the
polishing pad 2 while the wafer W is polished.
[0078] FIG. 6A illustrates vertical movement of the coupling member
75 relative to the spherical bearing 85, while FIGS. 6B and 6C
illustrate tilt movement of the coupling member 75 together with
the inner ring 101. The retainer ring 40 coupled to the coupling
member 75 is tiltably movable together with the inner ring 101 at
the fulcrum O, and is vertically movable relative to the inner ring
101.
[0079] FIG. 7 is an enlarged cross-sectional view illustrating
another configuration example of a spherical bearing 85. As shown
in FIG. 7, the spherical bearing 85 includes an intermediate ring
91 coupled to a retainer ring 40 via a coupling member 75, an outer
ring 92 slidably supporting the intermediate ring 91 from above,
and an inner ring 93 slidably supporting the intermediate ring 91
from beneath. The intermediate ring 91 has a partial spherical
shell shape where a lower half thereof is smaller than an upper
half, the intermediate ring 91 being interposed between the outer
ring 92 and the inner ring 93.
[0080] The outer ring 92 is arranged in a recessed portion 43b. The
outer ring 92 has a brim 92a at an outer periphery of the outer
ring 92, through which brim 92a, by securing the brim 92a onto a
step of the recessed portion 43b with a bolt (not shown), the outer
ring 92 is fixed to the carrier 43, as well as pressure can be
applied onto the intermediate ring 91 and the inner ring 93. The
inner ring 93 is arranged on a bottom of the recessed portion 43b
to support from beneath the intermediate ring 91 so as to form a
gap between a lower surface of the intermediate ring 91 and the
bottom of the recessed portion 43b.
[0081] An inner surface 92b of the outer ring 92, an outer surface
91a and an inner surface 91b of the intermediate ring 91, and an
outer surface 93a of the inner ring 93 are each configured in an
approximate hemispherical shape formed around a fulcrum O. The
outer surface 91a of the intermediate ring 91 slidably contacts
with the inner surface 92b of the outer ring 92, while the inner
surface 91b of the intermediate ring 91 slidably contacts with the
outer surface 93a of the inner ring 93. The inner surface 92b
(sliding contact surface) of the outer ring 92, the outer surface
91a and the inner surface 91b (sliding contact surfaces) of the
intermediate ring 91, and the outer surface 93a (sliding contact
surface) of the inner ring 93 each has a partial spherical shape
where a lower half thereof is smaller than an upper half. According
to the above described configuration, the intermediate ring 91 is
tiltably and omni-directionally) (360.degree.) movable relative to
the outer ring 92 and the inner ring 93, and the fulcrum O, i.e. a
center of tilt movement, positions below the spherical bearing
85.
[0082] The outer ring 92, the intermediate ring 91, and the inner
ring 93 are respectively formed with through holes 92c, 91c, and
93b into which a shaft 76 is inserted. A gap is formed between the
through hole 92c of the outer ring 92 and the shaft 76, as well as
another gap is formed between the through hole 93b of the inner
ring 93 and the shaft 76. The through hole 91c of the intermediate
ring 91 has a smaller diameter than diameters of the respective
through holes 92c and 93b of the outer ring 92 and the inner ring
93 so that the shaft 76 is only longitudinally movable relative to
the intermediate ring 91. The retainer ring 40 coupled to the shaft
76 therefore cannot substantially move laterally, and a lateral
(horizontal) position of the retainer ring 40 is secured by the
spherical bearing 85.
[0083] FIG. 8A illustrates vertical movement of the coupling member
75 relative to the spherical bearing 85, while FIGS. 8B and 8C
illustrate tilt movement of the coupling member 75 together with
the intermediate ring 91. As shown in FIGS. 8A to 8C, the retainer
ring 40 coupled to the coupling member 75 is tiltably movable
together with the intermediate ring 91 at the fulcrum O, as well as
is vertically movable relative to the intermediate ring 91. The
spherical bearing 85 shown in FIG. 7 is the same with the spherical
bearing 85 shown in FIG. 5 in terms of the fulcrum O, i.e. a center
of tilt movement, positioned on a central axis line of the retainer
ring 40. However, the spherical bearing 85 shown in FIG. 7 is
different from the spherical bearing 85 shown in FIG. 5 because the
fulcrum O shown in FIG. 7 is positioned lower than the fulcrum O
shown in FIG. 5. For the spherical bearing 85 shown in FIG. 7, a
height of the fulcrum O may be the same or below a surface of the
polishing pad 2.
[0084] Next, the retainer ring 40, which is one of features of the
present embodiment, will now be described herein.
[0085] FIG. 9 is an enlarged partial cross-sectional view of the
retainer ring 40. The retainer ring 40 includes an inside ring 40a
and an outside ring 40b. The inside ring 40a has an annular shape,
enclosing the wafer W. The outside ring 40b also has an annular
shape, and is arranged outside the inside ring 40a.
[0086] When polishing the wafer W, an inner peripheral surface of
the inside ring 40a comes into contact with the edge of the wafer
W. To prevent the wafer W from being chipped or damaged, the inside
ring 40a is molded of a softer material than the wafer W,
preferably a material having a Rockwell M hardness of in a range
from a minimum of 70 to a maximum of 120. In addition, the inner
peripheral surface of the inside ring 40a receives a force from the
edge of the wafer W. To bear such a force, the inside ring 40a is
molded of a highly abrasion-resistant material. Highly
abrasion-resistant materials having low hardness property may be,
for example, PPS (Poly Phenylene Sulfide), PEEK (Poly Ether Ether
Ketone), PTFE (Poly Tetra Fluoro Etylene), PP (Poly Propylene), PET
(Polyethylene Terephthalate), polycarbonate, polyacetal, and other
resin materials that contain one or more of the described
materials.
[0087] A lower surface of the outside ring 40b is pressed by the
polishing face 2a to be rotated. Therefore, the outside ring 40b is
molded of a material that is more abrasion-resistant than a
material of the inside ring 40a, preferably a material with a wear
amount, due to contact with the polishing face 2a, of a maximum of
one fifth of a wear amount of the inside ring 40a. Such a material
may be, for example, a ceramic material, such as SiC, SiN, alumina,
or zirconia, or a metallic material, such as stainless steel or
titanium. The material of the outside ring 40b may be harder than a
material of the inside ring 40a.
[0088] The retainer ring 40 normally requires breaking-in polishing
in an initial stage of use to stabilize surface roughness of a
lower surface that comes into contact with the polishing face 2a,
because, if the retainer ring 40 having a rough surface is used
when polishing the wafer W, an action of grinding a surface of the
polishing pad 2 occurs, leading to an unstable polishing rate of
the wafer W. Since the outside ring 40b is highly
abrasion-resistant, and will be rarely worn in a polishing process,
it is preferable that surface roughness be a maximum of Ra 1.6
.mu.m (JIS B 0601:2001) in an initial state.
[0089] FIG. 10 is a view schematically illustrating a change in a
surface shape of the retainer ring 40 shown in FIG. 9 after used
for a long period of time. The view shows that the lower surface of
the retainer ring 40 wears through contact with the polishing face
2a, where wear on the inner peripheral surface of the inside ring
40a due to contact with the edge of the wafer W is ignored. Wear on
a lower surface of the inside ring 40a advances through polishing
of many wafers W in a long period of time due to contact with the
polishing face 2a. In particular, the more close to the inner
peripheral surface, the more the wear amount, and the more close to
an outer periphery (i.e. more close toward the outside ring 40b),
the less the wear amount. On the other hand, since the outside ring
40b is molded of a highly abrasion-resistant material, the lower
surface is not changed significantly, almost keeping the initial
shape.
[0090] With the retainer ring 40 having such a shape, an innermost
point A on the lower surface of the outside ring 40b becomes a load
acting point against the wafer W. Accordingly, the load acting
point can be prevented from being moved away from the edge of the
wafer W. As a result, even when the retainer ring 40 is used for a
long period of time, a polishing rate at the edge of the wafer W
can be prevented from being increased, achieving the stabilized
polishing rate.
[0091] An appropriate value of thickness d of the inside ring 40a
in a radial direction will now be described herein.
[0092] Since the inner peripheral surface of the inside ring 40a
wears due to contact with the wafer W, a thickness d must be
thicker than a wear amount.
[0093] FIGS. 11A to 11D are graphs showing measurement results of
cross sectional shapes of a typical retainer ring after used for a
long period of time. The typical retainer ring is molded of a
single material (PPS), different from the retainer ring 40
including the inside ring 40a and the outside ring 40b shown in
FIG. 9. FIGS. 11A to 11D respectively show the results of measuring
the annular retainer ring at four points shifted by 90 degrees (0
deg., 90 deg., 180 deg., and 270 deg., respectively).
[0094] Horizontal axes of FIGS. 11A to 11D each represents position
R of the retainer ring in a radial direction, indicating that an
inner peripheral surface of the unworn retainer ring is positioned
at a value of 90 .mu.m. Vertical axes each represents height Z of
the retainer ring, indicating that a lower surface of the retainer
ring is positioned at a value of 800 .mu.m, and an edge of a wafer
W is coming into contact with a value of approximately 400
.mu.m.
[0095] As can be seen in the measurement results, the retainer ring
wears approximately 0.04 mm after used for a long period of time.
When using the retainer ring 40 configured with the inside ring 40a
and the outside ring 40b, a preferable thickness d of the inside
ring 40a be a minimum of 0.05 mm by taking into account some
additional thickness because the inside ring 40a could be worn 0.04
mm. The thickness d of the inside ring 40a may be increased
further, for example, a minimum of 0.1 mm, because a too thin
thickness might be disadvantageous in terms of rigidity, as well as
might lead to difficult processing.
[0096] On the other hand, although the load acting point of the
retainer ring 40 is the innermost point A on the lower surface of
the outside ring 40b, a too high thickness d causes the load acting
point of the retainer ring 40 to move away from the edge of the
wafer W, leading to an unstable polishing rate. Therefore, the
thickness d is set so that the load acting point of the retainer
ring 40 comes close to the edge of the wafer W.
[0097] FIGS. 12 to 14 are graphs showing measurement results of
shapes of lower surfaces of typical retainer rings after used for a
long period of time. The retainer rings used for the measurements
were also molded of a single material (PPS), where the lower
surfaces were flat initially. As can be seen in the graphs, widths
of the retainer rings (distances in a radial direction between an
inner peripheral surface and an outer peripheral surface) were 5 mm
(FIG. 12), 7.5 mm (FIG. 13), and 15 mm (FIG. 14). A horizontal axis
of each of the graphs represents positions in radial direction
relative to the inner peripheral surface of the retainer ring as an
origin. A vertical axis represents a relative distance from the
polishing face 2a, where a scale represents 10 .mu.m. As can be
seen, although the lower surfaces of the retainer rings were flat
initially, the lower surfaces were worn after use for a long period
of time, forming a downwardly raised portion (convex portion) P' on
the lower surface.
[0098] Regarding the retainer rings with the initial widths of 5 mm
(FIGS. 12) and 7.5 mm (FIG. 13), respectively, polishing rates were
stable, and wafers W were polished successfully. On the other hand,
regarding the retainer ring with the initial width of 15 mm (FIG.
14), a polishing rate was unstable, resulting in unsuccessful
polishing of a wafer W.
[0099] According to FIGS. 12 and 13 where proper polishing was
realized, distances s' between the inner peripheral surfaces and
the downwardly raised portions P' of the retainer rings were
approximately 3 mm and 5 mm, respectively. The results mean, for
the retainer ring 40 including the inside ring 40a and the outside
ring 40b shown in FIG. 10, that a maximum thickness d of 5 mm can
achieve a stabilized polishing rate.
[0100] On the other hand, according to FIG. 14 where proper
polishing was not realized, the distance s' between the inner
peripheral surface and the downwardly raised portion P' of the
retainer ring was approximately 7 mm. The result means, for the
retainer ring 40 shown in FIG. 10, that a minimum thickness d of 7
mm could lead to an unstable polishing rate.
[0101] Therefore, it is preferable that a thickness d should not be
too high, but be below 7 mm, and more preferably a maximum of 5
mm.
[0102] As shown in FIG. 9, although the lower surface of the
outside ring 40b may be flat, it is preferable that a downwardly
raised portion be formed toward the polishing face 2a (lower
side).
[0103] FIGS. 15A to 15F are enlarged views of various outside rings
40b. In the views, inside rings 40a are illustrated with two-dot
chain lines. A downwardly raised portion P may be formed at an
innermost side of an outside ring 40b (FIGS. 15A and 15D), or may
be formed at a position slightly away from the innermost side
(FIGS. 15B and 15E). In addition, lines from a downwardly raised
portion P to both ends of a lower surface of an outside ring 40b
may be straight (FIGS. 15A and 15B) or curved (FIGS. 15D and
15E).
[0104] By providing a downwardly raised portion P at a position
near an inside ring 40a, the downwardly raised portion P becomes a
load acting point against a wafer W. Accordingly, the load acting
point is prevented from being moved away from a wafer W in a radial
direction.
[0105] As shown in FIGS. 15C and 15F, downwardly raised portions P
may be at outermost positions of outside rings 40b (or near
outside). In each case of FIGS. 15C and 15F, an innermost point on
an outside ring 40b becomes a load acting point against a wafer W,
maintaining the load acting point near the wafer W as well.
[0106] When a distance h between an end (where no downwardly raised
portion P is formed) of an outside ring 40b and a downwardly raised
portion P is too large, a load could concentrate into the
downwardly raised portion P, leading to an unstable polishing rate,
the worn downwardly raised portion P, and the damaged polishing
face 2a.
[0107] According to FIGS. 12 and 13 where proper polishing was
realized, distances h' between tips of downwardly raised portions
P' and ends of retainer rings, the distances h' being occurred due
to wear, were approximately 5 .mu.m and 20 .mu.m, respectively. The
results mean, for the retainer ring 40s, shown in FIGS. 15A to 15F
where downwardly raised portions P are formed, that an acceptable
distance h is a maximum of 20 .mu.m.
[0108] On the other hand, according to FIG. 14 where proper
polishing was not realized, the distance h' was approximately 30
.mu.m. The result means, for the retainer rings 40 shown in FIGS.
15A to 15F, that a polishing rate becomes unstable if the distance
h is a minimum of 30 .mu.m. In other words, a maximum distance h of
30 .mu.m can prevent a load from being excessively concentrated at
a downwardly raised portion P.
[0109] Therefore, it is preferable, for the retainer rings 40, that
a distance h be below 30 .mu.m, and more preferably, a maximum of
20 .mu.m.
[0110] Based on the above information, it is preferable that a
thickness d of the inside ring 40a in a radial direction shown in
FIG. 10 be in a range from a minimum of 0.05 mm to a maximum of 5
mm. When arranging a downwardly raised portion P on a lower surface
of the outside ring 40b, it is preferable that a distance h between
an end of the outside ring 40b and a tip of a downwardly raised
portion P be below 30 .mu.m.
[0111] FIG. 16 is a cross-sectional view illustrating an example
method for fixing an inside ring 40a and an outside ring 40b. The
inside ring 40a and the outside ring 40b may be fixed using an
adhesive agent. However, it is preferable that a screw 40c be used
so that the inside ring 40a is detachable from the outside ring
40b. As shown in FIG. 10, the inside ring 40a could wear due to
contact with the polishing face 2a, while the outside ring 40b
rarely wears. By making the inside ring 40a detachable, only the
inside ring 40a can be replaced, if worn, in a cost effective
manner.
[0112] The inside ring 40a and the outside ring 40b are fixed each
other at least when polishing a wafer W so as to vertically move
together.
[0113] A specific configuration example of FIG. 16 shows that the
cross sections of the inside ring 40a and the outside ring 40b are
L-shaped which can be engaged each other. Screw holes are formed in
portions where the inside ring 40a and the outside ring 40b abut in
a vertical direction. Through the screw holes, a screw 40c is
tightened to secure the inside ring 40a and the outside ring 40b. A
screw hole 40d is formed on the outside ring 40b to fix the
retainer ring 40 onto the drive ring 81 by inserting one of the
plurality of screws 83 shown in FIG. 3C.
[0114] Although this configuration only represents an example, it
is obvious that those skilled in the art will understand that there
are various methods of detachably fixing the inside ring 40a and
the outside ring 40b.
[0115] When replacing the inside ring 40a as a maintenance, firstly
the screw 40c is removed to remove the inside ring 40a from the
outside ring 40b. Next, a new inside ring 40a is fit onto the
outside ring 40b, and then again the screw 40c is tightened to fix
the inside ring 40a and the outside ring 40b.
[0116] It is unnecessary to always fix the inside ring 40a and the
outside ring 40b each other, but the inside ring 40a and the
outside ring 40b may be vertically moved individually. In this
case, a force pressing the inside ring 40a onto the polishing face
2a, and another force pressing the outside ring 40b onto the
polishing face 2a may be the same, or may be different. For
example, the outside ring 40b may be more strongly pressed onto the
polishing face 2a. In contrast, the outside ring 40b may be more
gently pressed onto the polishing face 2a, or the outside ring 40b
may be contact-less with the polishing face 2a, if required.
[0117] When the outside ring 40b is pressed onto the polishing face
2a separately from the inside ring 40a, an amount of wear of the
inside ring 40a in a vertical direction can be refrained, comparing
with a case where no outside ring 40b is provided, because,
although a wear amount of the inside ring 40a increases since an
outer periphery of the inside ring 40a strongly comes into contact
with the polishing pad 2 when no outside ring 40b is provided, the
outer periphery of the inside ring 40a can more gently come into
contact with the polishing pad 2 when an outside ring 40b is
provided.
[0118] FIG. 17 is an enlarged partial cross-sectional view of a
retainer ring 40', a modified example of the retainer ring 40 shown
in FIG. 9. An outside ring 40b of the retainer ring 40' includes a
lower ring 40b1 and an upper ring 40b2.
[0119] Since the lower ring 40b1 comes into contact with the
polishing face 2a, the lower ring 40b1 is molded of a highly
abrasion-resistant, chemically stable material, such as a ceramic
material, than a material of an inside ring 40a. Since the upper
surface of the upper ring 40b2 is mechanically fixed to the drive
ring 81 with a reinforcing pin 82, a screw 83 and the like (FIGS.
3B and 3C), the upper ring 40b2 is molded of a tougher
(damage-resistant, or, rigid) material, such as a stainless steel
metallic material or a resin material, than a material of the lower
ring 40b1. The lower ring 40b1 and the upper ring 40b2 may be fixed
each other with screws or an adhesive agent.
[0120] FIG. 18 is a bottom view of a retainer ring 40. As shown in
FIG. 18, a plurality of grooves 40d communicating the inside ring
40a and the outside ring 40b and extending in radial directions are
formed at an approximately even interval so that a polishing liquid
supplied onto the polishing face 2a can flow, through the plurality
of grooves 40d, from inside to outside, and vice versa, of the
retainer ring 40 for efficient polishing of a wafer W.
[0121] As described above, configuring the retainer ring 40 in two
pieces, i.e. the inside ring 40a and the outside ring 40b, while
using a highly abrasion-resistant material for the outside ring
40b, allow a load acting point of the retainer ring 40 to be kept
close to an edge of the wafer W, stabilizing a rate of polishing
the wafer W (the edge, particularly).
[0122] While the embodiment has been described above, the present
invention is not limited to the embodiment, and various other
changes and modifications can be made within the spirit of the
technology.
* * * * *