U.S. patent application number 09/840074 was filed with the patent office on 2001-10-25 for polishing apparatus.
Invention is credited to Kimura, Norio.
Application Number | 20010034198 09/840074 |
Document ID | / |
Family ID | 18634112 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034198 |
Kind Code |
A1 |
Kimura, Norio |
October 25, 2001 |
Polishing apparatus
Abstract
A polishing apparatus for polishing a plate-like workpiece by
way of a relative sliding motion between the plate-like workpiece
and a polishing surface. The polishing apparatus comprises a
carrier for holding the plate-like workpiece. The carrier comprises
a carrier body having a flat surface and one or more recesses
formed in the carrier body surface, an inner sheet covering the
carrier body surface and having an outer peripheral edge sealingly
connected to the carrier body, an outer sheet covering the inner
sheet and having an outer peripheral edge sealingly connected to
the carrier body, and a pressure supply device for providing
selectively a negative pressure or a positive pressure between the
inner sheet and the carrier body surface so that, upon provision of
the negative pressure, a suction force is created on the outer
surface of the outer sheet to draw a workpiece against the outer
sheet and, when applied the positive pressureacts on the workpiece
through the inner and outer sheets to press the workpiece against
the polishing surface.
Inventors: |
Kimura, Norio;
(Kanagawa-ken, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
18634112 |
Appl. No.: |
09/840074 |
Filed: |
April 24, 2001 |
Current U.S.
Class: |
451/285 ;
451/287; 451/398 |
Current CPC
Class: |
B24B 37/32 20130101;
B24B 37/30 20130101 |
Class at
Publication: |
451/285 ;
451/287; 451/398 |
International
Class: |
B24B 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2000 |
JP |
123891/2000 |
Claims
What is claimed is:
1. A polishing apparatus for polishing a plate-like workpiece by a
relative sliding motion between the workpiece and a polishing
surface, the polishing apparatus comprising a carrier for holding
the workpiece to bring the workpiece into contact with the
polishing surface, the carrier comprising: a carrier body having a
carrier surface and one or more recesses or openings formed in the
carrier body surface; an inner sheet positioned adjacent to the
surface of the carrier body and covering the carrier body surface,
the inner sheet being non-porous and having an outer peripheral
edge sealingly connected to the carrier body; an outer sheet
positioned adjacent to and covering the inner sheet, the outer
sheet having openings extending from an inner surface of the outer
sheet to an outer surface of the same, and an outer peripheral edge
sealingly connected to the carrier body; and a pressure supply
device for providing a negative pressure between the inner sheet
and the carrier body surface so that a suction force is created on
the outer surface of the outer sheet to draw a workpiece against
the outer sheet.
2. A polishing apparatus as set forth in claim 1, in which said
pressure supply device is capable of providing a positive pressure
between the inner sheet and the carrier body surface so that it
acts the workpiece through the inner and outer sheets to press the
workpiece against the polishing surface.
3. A polishing apparatus as set forth in claim 2, in which the
inner sheet is made of a flexible material and the outer sheet is
made of a relatively rigid material so that, upon provision of the
negative pressure between the carrier body surface and the inner
sheet, the inner sheet is partially deformed into the recesses or
the openings in the carrier body surface to form spaces between the
deformed portions of the inner sheet and the outer sheet in which
spaces a secondary negative pressure is generated, the secondary
negative pressure being transferred through the openings formed in
the outer sheet to the outer surface of the outer sheet thereby
drawing a workpiece against the outer surface of the outer sheet,
while, upon provision of the positive pressure, the inner sheet is
urged against the outer sheet by the positive pressure to press a
workpiece held on the outer surface of the outer sheet against the
polishing surface.
4. A polishing apparatus as set forth in claim 1, further including
a negative pressure supply device adapted to be fluidly
communicated with the spaces formed between the deformed portions
of the inner sheet and the outer sheet.
5. A polishing apparatus as set forth in claim 2, further including
a negative pressure supply device adapted to be fluidly
communicated with the spaces formed between the deformed portions
of the inner sheet and the outer sheet.
6. A polishing apparatus as set forth in claim 2 further comprising
a pressure ring provided around the carrier body in such a manner
that the pressure ring can move vertically independently of the
carrier body to independently press the polishing surface.
7. A polishing apparatus as set forth in claim 3 further comprising
a pressure ring provided around the carrier body in such a manner
that the pressure ring can move vertically independently of the
carrier body to independently press the polishing surface.
8. A polishing apparatus as set forth in claim 4 further comprising
a pressure ring provided around the carrier body in such a manner
that the pressure ring can move vertically independently of the
carrier body to independently press the polishing surface.
9. A polishing apparatus as set forth in claim 4 in which the
carrier body has a circumferential surface extending from the
carrier body surface at a predetermined angle in a direction away
from the polishing surface and the circumferential surface is
provided with a passage having one end adapted to be connected to
the negative pressure supply device and the other end fluidly
connected to the recesses formed in the carrier body surface.
10. A polishing apparatus as set forth in claim 4 in which the
carrier body has a circumferential surface extending from the
carrier body surface at a predetermined angle in a direction away
from the polishing surface and the circumferential surface is
provided with a passage having one end adapted to be connected to
the negative pressure supply device and the other end fluidly
connected to the recesses formed in the carrier body surface.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a polishing apparatus for
polishing a plate-like article such as a semiconductor wafer or an
optical lens.
[0002] In manufacturing integrated circuits, optical devices and
the like, it is important that a workpiece used to form an
integrated circuit, optical device or the like have a highly planar
surface. Recently, a polishing technique referred to as "Chemical
Mechanical Polishing (CMP)" has been commonly employed in polishing
semiconductor wafers. In Chemical Mechanical Polishing, a
semiconductor wafer held by a rotating carrier body is brought into
contact with a polishing surface provided on a rotating turntable
while an alkali or acid abrasive slurry is supplied onto the
polishing surface, whereby the wafer is polished both mechanically
under relative motion between the rotating carrier body and the
rotating turntable, and chemically by the supplied slurry. In this
way, the wafer surface can be polished to an exceptionally high
degree of flatness. However, it is important that the surface of
the carrier body which is used to hold and press the wafer against
the turntable polishing surface also be uniformly flat, and that a
force applied in pressing the wafer against the polishing surface
be applied across the surface of the wafer uniformly. It has been
difficult to meet this requirement.
[0003] One method which has been developed involves covering the
surface of a carrier body with a resilient membrane and forming a
pressurized fluid chamber between the inner membrane surface and
the carrier body surface. In a polishing operation, a wafer held on
the outer surface of the membrane is pressed against the polishing
surface under a fluid pressure supplied into the fluid chamber to
impart a uniform pressure across the wafer surface. To hold the
wafer on the membrane surface during transfer to and from the
polishing surface, a negative pressure is generated between the
wafer and the membrane by making the latter surface concave.
However, this method is subject to a problem that when a negative
pressure acts on a wafer causing it to bend, if even minute defects
exist on the wafer's surface, the wafer may break. A solution to
this problem has been desired.
SUMMARY OF THE INVENTION
[0004] The object of the present invention is to provide a
polishing apparatus in which a workpiece such as a semiconductor
wafer or the like is securely held on a carrier body surface under
a suction force. This suction force is applied during transfer of
the workpiece to and from a polishing surface, and when it is
brought into contact with the polishing surface a positive pressure
is provided which acts across the surface of the workpiece
uniformly, whereby a high degree of flatness of the workpiece
surface can be attained.
[0005] According to one aspect of the present invention, a
polishing apparatus comprises a carrier for holding a plate-like
workpiece and bringing it into contact with a polishing surface.
The carrier comprises a carrier body having a flat surface and one
or more recesses formed in the carrier body surface, a non-porous
inner sheet provided adjacent to the carrier body surface and
covering it, an outer sheet covering the inner sheet, with openings
extending from the inner to outer surface of the outer sheet, and a
pressure supply device for generating selectively a negative or
positive pressure between the inner sheet and the carrier body
surface. The inner and outer sheets are sealingly connected to the
carrier body along their outer peripheral edges. When a negative
pressure is generated between the inner sheet and the carrier body
surface, a suction force acts on the outer surface of the outer
sheet to draw a workpiece against it. If a positive pressure is
provided, it acts on the workpiece through the inner and outer
sheets and presses it against the polishing surface.
[0006] Since the inner sheet is made of a flexible material and the
outer sheet of a relatively rigid material, when a negative
pressure is provided, it causes a portion of the inner sheet to
deform, and this deformed portion enters the recesses in the
carrier body surface, with the result that spaces are formed
between the deformed portions of the inner sheet and the outer
sheet. In these spaces, a secondary negative pressure is generated
and transferred through the openings formed in the outer sheet to
the outer surface of the outer sheet to draw a workpiece against
this outer surface. In contrast, if a positive pressure is
provided, it acts to urge the inner sheet against the outer sheet
thereby pressing a workpiece held on the outer surface of the outer
sheet against the polishing surface.
[0007] The polishing apparatus further includes a negative pressure
or vacuum supply device adapted to be fluidly communicated with the
spaces formed between the deformed portions of the inner sheet and
the outer sheet. Specifically, the carrier body is provided with a
circumferential surface extending from the carrier body surface at
a predetermined angle in a direction away from the polishing
surface when the carrier is positioned for polishing a workpiece,
and the circumferential surface is provided with a passage having
one end adapted to be connected to the negative pressure supply
device and the other end fluidly connected to the recesses formed
in the carrier body surface. The negative pressure provided by the
negative pressure supply device enables the workpiece to be held
securely against the outer sheet.
[0008] Further, a pressure ring is provided around the carrier in
such a manner as to be able to move vertically independently of the
carrier to press against the polishing surface. Preferably, the
pressure ring depresses the polishing surface to the same level as
that of an area of a workpiece to be polished to avoid an excessive
force being imposed on the edge of workpiece when the rotating
polishing surface comes into contact with the rotating
workpiece.
[0009] These and other features and advantages of the present
invention will become apparent from the following detailed
description of the invention when taken in conjunction with the
accompanying drawings wherein like reference numerals designate
like or corresponding elements throughout the several views.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a sectional view of a main part of a polishing
apparatus in accordance with the present invention.
[0011] FIG. 2 is a bottom view of a carrier body of the polishing
apparatus of FIG. 1.
[0012] FIG. 3 is a cross-sectional view of a part of the polishing
apparatus of FIG. 1 showing a relationship between inner and outer
sheets of the polishing apparatus and a semiconductor wafer.
[0013] FIG. 4 is a bottom view of the outer sheet.
[0014] FIG. 5 is a cross-sectional view of a part of the polishing
apparatus showing a relationship between the inner and outer sheets
and a wafer during polishing of the wafer.
[0015] FIG. 6 is a cross-sectional view of a part showing
peripheral edge portions of the inner and outer sheets and a vacuum
passage for applying a vacuum between the inner and outer
sheets.
[0016] FIG. 7 is a schematic view of a polishing apparatus in
accordance with another embodiment of the present invention.
[0017] FIG. 8 is an enlarge cross-sectional view of a main part of
the polishing apparatus of FIG. 7.
[0018] FIG. 9 is a bottom view of a carrier body in accordance with
a further embodiment of the present invention.
[0019] FIG. 10 is a cross-sectional view of a part of the carrier
body provided with inner and outer sheets covering the bottom
surface of the carrier body showing a relationship between the
inner and outer sheets and a wafer during polishing of the
wafer.
DETAILED DESCRIPTION OF THE INVENTION
[0020] With reference to the drawings, embodiments of the present
invention will be explained below. FIGS. 1-6 show one embodiment of
the present invention. In this embodiment, a polishing apparatus 10
is used for polishing semiconductor wafers W and includes, as
shown, a turntable 14 and a wafer carrier 20 for holding the
semiconductor wafer W and pressing the wafer against a polishing
pad 16 provided on an upper surface of the turntable 14.
[0021] In a polishing operation, the turntable 14 and the wafer
carrier 20 are rotated by drive shafts 22 and 24 respectively
whereby a sliding motion occurs between the wafer W and the
polishing pad 16, with an alkali abrasive slurry being supplied by
a nozzle (not shown) onto the polishing pad 16, thereby conducting
chemical mechanical polishing of the semiconductor wafer.
[0022] The wafer carrier comprises, as shown in FIG. 1, a disk-like
carrier body 26 drivingly connected to the drive shaft 24, a
flexible non-porous inner sheet 32 configured to be substantially
in contact with and cover an entire area of a carrier body surface
or lower surface of the carrier body 26 facing the turntable 14,
and a flexible porous outer sheet 34 configured to be substantially
in contact with and cover an entire area of the inner sheet 32.
[0023] The rotational drive shaft 24 and the carrier body 26 are
provided with a fluid passage 38 having one end opening formed in
the carrier body surface 30 and the other end fluidly connected to
a fluid pressure source (not shown). As shown in FIGS. 1 and 2, the
wafer carrier body surface 30 has a center circular recess 40
provided at the center thereof and fluidly communicated with the
fluid passage 38, five concentric annular recesses or grooves 42
which are concentric with the center circular recess 40 and spaced
away from each other, and four straight radial recesses 44
extending at ninety degree intervals from the center circular
recess 40 to fluidly connect the center circular recess 40 with the
annular recesses 42.
[0024] In accordance with the embodiment, the carrier body 26 is
fixedly provided on its circumferential surface with a retainer
ring holder 54 to hold a retainer ring 56 at its lower end in order
to prevent the semiconductor wafer W being displaced from the
carrier. The outer peripheral portions of the inner and outer
sheets 32, 34 are clamped between the circumferential surface of
the carrier body 26 and the retainer ring holder 54 to fasten the
inner and outer sheets 32, 34 to the carrier body 26.
[0025] To hold a semiconductor wafer W on the wafer carrier 20 for
transferring the wafer W onto the polishing pad 16 of the turntable
for polishing of the wafer or to transfer or remove the same from
the polishing pad after the polishing, a vacuum is applied to a
space between the wafer carrier body surface 30 and the inner sheet
32 from a vacuum source (not shown) through the fluid passage 38
and the recesses formed in the wafer carrier body surface including
the central circular recess 38, the annular recesses 42 and the
straight radial recesses 44. As a consequence, the inner sheet 32
is drawn against the wafer carrier body surface 30 so that the
recesses 38, 42, 44 draw portions of the inner sheet 32
corresponding to those recesses thereinto, thereby forming spaces c
between the drawn portions of the inner sheet 32 and the outer
sheet 34. A negative pressure is thus generated in the spaces c,
and transferred to the outer surface of the outer sheet 34 through
pores in the sheet member 34 to create a suction force to draw the
semiconductor wafer W against the outer surface of the outer sheet
34. The porous outer sheet 34 may be replaced with a non-porous
sheet member provided with a plurality of, for example, as shown in
FIG. 4, twenty through-holes spaced apart from each other and
provided along the recesses 44 in the wafer carrier body surface
30.
[0026] In this case, it is desirable to apply a vacuum to spaces c
formed between the inner and outer sheets 32, 34. To this end, as
shown in FIGS. 2 and 6, the carrier body 26 is provided on its
outer circumferential surface with fluid passages 60 at ninety
degree intervals fluidly connected to the corresponding radial
recesses 44 formed in the wafer carrier body surface 30. As best
shown in FIG. 6, the carrier body 26 is provided along its upper
peripheral edge with a stepped recess portion 62 with the vertical
passage 60 fluidly connected to the stepped recess portion 62. The
inner and outer sheets 32, 34 are bent upwardly at the lower
peripheral edge of the carrier body 26 and extend upward along the
circumferential surface of the carrier body 26. The peripheral edge
portion of the inner sheet 32 is further bent radially inwardly at
the stepped recess portion 62 to extend onto the surface of the
stepped recess portion 62, while the peripheral edge portion of the
outer sheet 34 is not bent at the stepped recessed portion and
extends upwards. A sheet retaining ring 67 is securely fitted in
the stepped recess portion so that the sheet retaining ring 67
fastens the peripheral edge portion of the inner sheet 32 between
the sheet retaining ring 67 and the wafer carrier body 26 and the
circumferential edge portion of the outer sheet 34 between the
sheet retaining ring 67 and the retainer ring 54. The sheet
retaining ring is formed with a passage 68 extending in a vertical
direction. The upper end of the passage 68 is adapted to be
connected to a vacuum source 66 and the lower end of the same is
aligned with one of the vertical passages 60 formed in the
circumferential surface of the carrier body 26. As stated above,
when a vacuum is applied to the passage 38 in the rotational drive
shaft 24, the negative pressure spaces c are formed between the
inner and outer sheets 32, 34 along the recesses 38, 42 and 44 and
thus along the vertical recesses 60, a vacuum is also applied to
the space c formed along the vertical passage 60 through the
passage 68 formed in the sheet retaining member 67. The vacuum is
within a range from -50 Kpa to -90 Kpa.
[0027] In a polishing operation, instead of a vacuum, a pressurized
fluid is supplied from the fluid pressure source to a space between
the wafer carrier body surface 30 of the wafer carrier body 26 and
the inner sheet 32 so that, as shown in FIG. 5, the inner sheet 32
is urged against the outer sheet 34. As a consequence, the wafer W
held by the carrier 20 is uniformly pressed against the polishing
pad 16 under a force imposed by the pressurized fluid through the
inner and outer sheets 32, 34. The pressure is preferably within a
range from 4.9 Kpa.about.49 Kpa (50.about.5000 g/cm.sup.2.
[0028] The inner sheet 32 is preferably made of an flexible
material so that, when a vacuum is applied as stated above, the
inner sheet 32 is easily deformed into the recesses 38, 42, 44, 60
formed on the wafer carrier body 26. Specifically, as a material of
the inner sheet 32, polyurethane or latex, for example, may be
used. In contrast, the outer sheet 34 is preferably made of a
relatively rigid material so that, even if the inner sheet 32 is
deformed as stated above, the outer sheet 34 does not follow the
deformation of the inner sheet 32 to form the spaces c between the
inner and outer sheets. Specifically, as a material of the outer
sheet, neprane rubber, silicon gum, urethane rubber, or fluoro
rubber, for example, may be used. In order to enable the outer
sheet 34 to, as shown in FIG. 6, expand towards the wafer held by
the wafer carrier, the outer sheet 34 may be provided in its
circumferential surface with pleats or the like.
[0029] FIG. 7 is a schematic view of a whole polishing apparatus in
accordance with another embodiment of the present invention and
FIG. 8 is a longitudinal cross sectional view of a main part of the
polishing apparatus.
[0030] The polishing apparatus is basically the same as that of the
afore-mentioned embodiment and comprises a turntable 14 provided
with a polishing pad 16, and a wafer carrier 20 having a wafer
carrier body surface 30 facing the polishing pad 14 of the
turntable. The wafer carrier 20 further includes a non-porous inner
sheet 32 provided over the wafer carrier body surface 30 and a
porous outer sheet 34 provided outside and adjacent to the inner
sheet 32 to cover the same. As shown, the polishing apparatus
includes a fluid pressure source 70 for providing a desired fluid
pressure between the wafer carrier body surface 30 and the inner
sheet 32. Specifically, the fluid pressure source 70 is adapted to
apply a vacuum between the wafer carrier body surface 30 and the
inner sheet 32. The vacuum draws the inner sheet 32 against the
wafer carrier body surface 30 so that the inner sheet 32 is subject
to a partial deformation into recesses 48 formed in the wafer
carrier body surface to form spaces, corresponding to the spaces c
referred to in the first embodiment, between the deformed portions
of the inner sheet 32 and the outer sheet 34. As a consequence, a
negative pressure is created in the spaces and transferred to the
outer surface of the outer sheet 34 through pores in the outer
sheet 34 to draw a wafer W against the outer surface of the outer
sheet 34. In this case, the spaces c may be subjected to a vacuum
of a vacuum source through a valve R1 to securely draw the wafer W
against the outer sheet 34. Further, the fluid pressure source 70
is adapted to supply a pressurized fluid between the wafer carrier
body surface 30 and the inner sheet 32. The pressurized fluid
expands the inner sheet 32 and, thus, the outer sheet 34 to thereby
press the wafer W on the outer surface of the outer sheet 34
against the polishing pad 16 of the turntable 14. The inner and the
outer sheets 32, 34 are fastened to the wafer carrier in the same
way as that in the afore-mentioned embodiment. In FIG. 7, reference
numeral 76 designates a motor mounted on a carrier body 77 and
adapted to drive a rotational drive shaft 24 of the wafer carrier
through a belt drive device 78. Reference numeral 80 designates an
actuator mounted on the carrier body 77 and adapted to move the
wafer carrier 20 and the rotational drive shaft 24 vertically.
[0031] This polishing apparatus is different from that of the
afore-mentioned embodiment in that a pressure ring 84 for carrier
body the surface polishing pad 16 is provided in place of the
retainer ring 56 which is securely provided on the wafer carrier
body 26, the pressure ring 84 being movable vertically
independently of the wafer carrier body 26. The pressure ring 84 is
provided in the carrier body 26 and is adapted to be subjected to a
downward pressing force by a bellows-type expansion member 86 which
is supplied with a pressurized fluid from the fluid pressure source
70. When the wafer W is polished under a relative motion between
the wafer held by the wafer carrier and the polishing pad, the
pressure ring 84 presses down the surface of the polishing pad 16
around the wafer in order to avoid excess friction which would
otherwise be exerted on the edge of the wafer by the polishing
pad.
[0032] FIGS. 8 and 9 show a carrier body 26 in accordance with a
further embodiment of the present invention. As shown, the carrier
body 26 is provided with a plurality of through holes 49 each
having an upper end opening which is adapted to be connected to a
fluid pressure source and a lower end opening facing an inner sheet
32 provided over the bottom surface of the carrier body 26. In this
embodiment, the inner sheet 32 and outer sheet 34 are formed of
flexible non-porous material and the outer sheet 34 is provided
with a plurality of holes as in the outer sheet 34 shown in FIG. 4
which holes are aligned with the lower end openings of the through
holes 41 of the carrier body 26. In this embodiment, the lower end
openings of the through holes 49 perform the same function as that
of the recesses 38, 42, 44 in the first embodiment in
operation.
[0033] In accordance with the present invention, a semiconductor
wafer or workpiece is subjected to a fluid pressure which is
uniform across the entire surface of the workpiece, whereby it is
pressed against the polishing pad through the inner and outer
sheets 32, 34 thereby enhancing uniformity of polishing of the
workpiece. Further, when a workpiece is held on the carrier 20 for
transfer thereof, the workpiece is drawn by a suction force applied
through the outer sheet 34 against the surface 30 of the carrier
body 26 which is generally flat, whereby the workpiece is prevented
from becoming curved under a suction force and, as a consequence,
breakage of the workpiece, which was liable to occur in the prior
art, is prevented.
[0034] It is to be understood that the apparatuses described above
are only exemplary and do not limit the scope of the invention, and
that various modifications can be made by those skilled in the art
that would fall under the scope of the invention.
* * * * *