U.S. patent application number 09/736137 was filed with the patent office on 2002-06-13 for apparatus and method for chemical mechanical planarization using a fixed-abrasive polishing pad.
Invention is credited to Dyer, Timothy S., Fruitman, Clinton O..
Application Number | 20020072307 09/736137 |
Document ID | / |
Family ID | 24958643 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020072307 |
Kind Code |
A1 |
Fruitman, Clinton O. ; et
al. |
June 13, 2002 |
Apparatus and method for chemical mechanical planarization using a
fixed-abrasive polishing pad
Abstract
A homogeneous polishing pad for chemical mechanical
planarization of a workpiece has a thickness of at least about 1
millimeter. The polishing pad is friable and includes an abrasive
material that is uniformly distributed throughout the pad. The
abrasive material exhibits abrasive behavior that does not degrade
significantly as the pad wears during planarization and
conditioning. In another embodiment, the homogenous polishing pad
has an average wear rate in the range of from less than 1
.mu.m/minute to about 10 .mu.m/minute.
Inventors: |
Fruitman, Clinton O.;
(Chandler, AZ) ; Dyer, Timothy S.; (Tempe,
AZ) |
Correspondence
Address: |
SNELL & WILMER L.L.P.
One Arizona Center
400 East Van Buren
Phoenix
AZ
85004-0001
US
|
Family ID: |
24958643 |
Appl. No.: |
09/736137 |
Filed: |
December 13, 2000 |
Current U.S.
Class: |
451/36 ;
451/41 |
Current CPC
Class: |
B24D 3/14 20130101; B24B
7/228 20130101; B24D 3/28 20130101 |
Class at
Publication: |
451/36 ;
451/41 |
International
Class: |
B24B 001/00 |
Claims
We claim:
1. A homogenous polishing pad for chemical mechanical planarization
of a workpiece having a thickness of at least about 1 millimeter,
wherein said pad is friable and comprises an abrasive material
uniformly distributed throughout said pad, and wherein said
abrasive material has abrasive characteristics that do not degrade
significantly as said pad wears during planarization and
conditioning.
2. The polishing pad of claim 1, further comprising a resin-bonded
material.
3. The polishing pad of claim 1, further comprising a
ceramic-bonded material.
4. The polishing pad of claim 1 having a thickness in the range of
from about 0.5 inches to about 1.5 inches.
5. The polishing pad of claim 1 having a thickness of about one
inch.
6. The polishing pad of claim 1, wherein said polishing pad is
subjected to motion relative to said workpiece.
7. The polishing pad of claim 6, wherein said motion is selected
from the group comprising linear motion, orbital motion, rotary
motion, linear and orbital motion, linear and rotary motion,
orbital and rotary motion, and linear, orbital and rotary
motion.
8. The polishing pad of claim 1, further comprising at least one
channel through which a fluid may flow.
9. The polishing pad of claim 1, wherein said polishing pad
comprises pores through which a fluid may flow.
10. The polishing pad of claim 1 having an average wear rate in the
range of from less than 1 .mu.m/minute to about 10
.mu.m/minute.
11. A method of chemical mechanical planarization of a workpiece
comprising: providing a homogenous polishing pad having a thickness
of at least about 1 millimeter and having a polishing surface,
wherein said polishing pad is friable and comprises abrasive
material uniformly distributed throughout said polishing pad, and
wherein said abrasive material exhibits abrasive behavior that does
not degrade significantly as said polishing pad wears during
planarizaton and conditioning; and pressing said polishing pad
against said workpiece while causing relative motion between said
polishing pad and said workpiece.
12. The method of claim 11, further comprising distributing a fluid
to said polishing surface of said polishing pad.
13. The method of claim 11, wherein said causing relative motion
comprises causing relative motion selected from the group
comprising linear motion, orbital motion, rotary motion, linear and
orbital motion, linear and rotary motion, orbital and rotary
motion, and linear, orbital and rotary motion.
14. The method of claim 11, wherein said providing a homogenous
polishing pad further comprises providing a homogenous polishing
pad having a thickness in the range of from about 0.5 inches to
about 1.5 inches.
15. The method of claim 11, wherein said providing a homogenous
polishing pad further comprises providing a homogenous polishing
pad having a thickness of about one inch.
16. The method of claim 12, wherein said providing a homogeneous
polishing pad further comprises providing a homogeneous polishing
pad having at least one channel through which said fluid may
flow.
17. The method of claim 12, wherein said providing a homogeneous
polishing pad further comprises providing a homogeneous polishing
pad having pores through which said fluid may flow.
18. The method of claim 11, wherein said providing a homogeneous
polishing pad further comprises providing a homogeneous polishing
pad having an average pad wear rate in the range of from less than
1 m/minute to about 10 .mu.m/minute.
19. An apparatus for planarizing a workpiece comprising: a
homogenous polishing pad having a thickness of at least about 1
millimeter, wherein said pad is friable and comprises abrasive
material uniformly distributed throughout, and wherein said
abrasive material exhibits abrasive behavior that does not degrade
significantly as said homogeneous polishing pad wears during
planarization and conditioning; and a workpiece carrier configured
to carry a workpiece and press said workpiece against said
homogeneous polishing pad.
20. The apparatus of claim 19, wherein said polishing pad has a
thickness in the range of from about 0.5 inches to about 1.5
inches.
21. The apparatus of claim 19, wherein said polishing pad has a
thickness of about one inch.
22. The apparatus of claim 19, further comprising a drive assembly
configured to cause relative motion between said polishing pad and
said workpiece.
23. The apparatus of claim 22, wherein said relative motion is
selected from the group comprising linear motion, orbital motion,
rotary motion, linear and orbital motion, linear and rotary motion,
orbital and rotary motion, and linear, orbital and rotary
motion.
24. The apparatus of claim 19, wherein said workpiece carrier
comprises a central axis and is configured to rotate about said
central axis.
25. The apparatus of claim 19, wherein said homogeneous polishing
pad has a polishing surface and at least one channel wherein fluids
are fed to said polishing surface through said at least one
channel.
26. The apparatus of claim 25, further comprising a platen
configured to support said polishing pad.
27. The apparatus of claim 26, wherein said platen comprises at
least one conduit and wherein fluids are fed to said polishing
surface through said at least one conduit of said platen and said
at least one channel of said homogeneous polishing pad.
28. The apparatus of claim 19, wherein said homogeneous polishing
pad has a polishing surface and comprises pores wherein fluids are
fed to said polishing surface through said pores.
29. The apparatus of claim 28, further comprising a platen
configured to support said polishing pad.
30. The apparatus of claim 29, wherein said platen comprises at
least one conduit and wherein fluids are fed to said polishing
surface through said at least one conduit of said platen and said
pores of said homogeneous polishing pad.
31. The apparatus of claim 19, wherein said homogeneous polishing
pad has an average wear rate in the range of from less than 1
.mu.m/minute to about 10 .mu.m/minute.
32. A homogeneous polishing pad for chemical mechanical
planarization of a workpiece having an average wear rate in the
range of from less than 1 .mu.m/minute to about 10 .mu.m/minute,
wherein said pad is friable and comprises an abrasive material
uniformly distributed throughout said pad, and wherein said
abrasive material has abrasive characteristics that do not degrade
significantly as said pad wears during planarization and
conditioning.
33. The polishing pad of claim 32, further comprising a
resin-bonded material.
34. The polishing pad of claim 32, further comprising a
ceramic-bonded material.
35. The polishing pad of claim 32, having a thickness in the range
of from about 0.5 inches to about 1.5 inches.
36. The polishing pad of claim 32, having a thickness of about one
inch.
37. The polishing pad of claim 32, wherein said polishing pad is
subjected to motion relative to said workpiece.
38. The polishing pad of claim 37, wherein said motion is selected
from the group comprising linear motion, orbital motion, rotary
motion, linear and orbital motion, linear and rotary motion,
orbital and rotary motion, and linear, orbital and rotary
motion.
39. The polishing pad of claim 32, further comprising at least one
channel through which a fluid may flow.
40. The polishing pad of claim 32, further comprising pores through
which a fluid may flow.
41. An apparatus for planarizing a workpiece comprising: a) a
plurality of polishing stations wherein at least one of said
plurality of polishing stations comprises a homogenous polishing
pad having a thickness of at least about 1 millimeter, wherein said
homogenous polishing pad is friable and comprises abrasive material
uniformly distributed throughout, and wherein said abrasive
material has abrasive characteristics that do not degrade
significantly as said polishing pad wears during planarization and
conditioning; and b) a drive assembly connected to said at least
one of said plurality of polishing stations and configured to
effect a first relative motion between said homogenous polishing
pad and said workpiece.
42. The apparatus of claim 41, wherein said first relative motion
is selected from the group comprising linear motion, orbital
motion, rotary motion, linear and orbital motion, linear and rotary
motion, orbital and rotary motion, and linear, orbital and rotary
motion.
43. The apparatus of claim 41, wherein said homogenous polishing
pad further comprises a resin-bonded material.
44. The apparatus of claim 41, wherein said homogenous polishing
pad further comprises a ceramic-bonded material.
45. The apparatus of claim 41, wherein said homogenous polishing
pad has a thickness in the range of from about 0.5 inches to about
1.5 inches.
46. The apparatus of claim 41, wherein said homogenous polishing
pad has a thickness of about one inch.
47. The apparatus of claim 41, wherein said homogenous polishing
pad has a least one channel through which a fluid may flow.
48. The apparatus of claim 41, wherein said polishing pad comprises
pores through which a fluid may flow.
49. The apparatus of claim 41, wherein said polishing pad has an
average wear rate in the range of from less than 1 .mu.m/minute to
about 10 .mu.m/minute.
50. The apparatus of claim 41, further comprising a conditioning
assembly configured to condition said homogenous polishing pad
after planarization of a workpiece.
51. The apparatus of claim 41, further comprising a conditioning
assembly configured to condition said homogenous polishing pad
during planarization of a workpiece.
52. The apparatus of claim 41, further comprising a plurality of
workpiece carriers, the number of which corresponds to the number
of said polishing stations, wherein each of said plurality of
workpiece carriers is configured to carry a workpiece and press
said workpiece against one of said plurality of polishing stations
while causing a second relative motion between said workpiece and
said polishing station.
53. The apparatus of claim 52, wherein said second relative motion
is selected from the group comprising linear motion, orbital
motion, rotary motion, linear and orbital motion, linear and rotary
motion, orbital and rotary motion, and linear, orbital and rotary
motion.
54. The apparatus of claim 41, wherein said homogenous polishing
pad has a polishing surface and at least one channel through which
fluids are fed to said polishing surface.
55. The apparatus of claim 54, wherein said at least one of said
plurality of polishing stations comprises a platen configured to
support said homogenous polishing pad.
56. The apparatus of claim 55, wherein said platen comprises at
least one conduit and wherein fluids are fed to said polishing
surface through said at least one conduit and said at least one
channel of said polishing pad.
57. The apparatus of claim 41, wherein said homogeneous polishing
pad has a polishing surface and comprises pores wherein fluids are
fed to said polishing surface through said pores.
58. The apparatus of claim 57, further comprising platen configured
to support said polishing pad.
59. The apparatus of claim 58, wherein said platen comprises at
least one conduit and wherein fluids are fed to said polishing
surface through said at least one conduit of said platen and said
pores of said homogeneous polishing pad.
60. An apparatus for planarizing a workpiece comprising: a
homogeneous polishing pad, wherein said polishing pad is friable
and has abrasive material uniformly distributed throughout, and
wherein said abrasive material exhibits abrasive behavior that does
not degrade significantly as said homogeneous polishing pad wears
during planarization and conditioning; a drive assembly configured
to move said polishing pad in an orbital pattern; and a workpiece
carrier configured to carry a workpiece and press said workpiece
against said homogeneous polishing pad.
61. The apparatus of claim 60, wherein said polishing pad has a
thickness of at least 1 millimeter.
62. The apparatus of claim 60, wherein said polishing pad has a
thickness in the range of from about 0.5 inches to about 1.5
inches.
63. The apparatus of claim 60, wherein said polishing pad has a
thickness of about one inch.
64. The apparatus of claim 60, wherein said workpiece carrier
comprises a central axis and is configured to rotate about said
central axis.
65. The apparatus of claim 60, wherein said homogeneous polishing
pad has a polishing surface and at least one channel wherein fluids
are fed to said polishing surface through said at least one
channel.
66. The apparatus of claim 65, further comprising a platen
configured to support the polishing pad.
67. The apparatus of claim 66, wherein said platen comprises at
least one conduit and wherein a fluid is fed to said polishing
surface through said at least one conduit and said at least one
channel.
68. The apparatus of claim 60, wherein said homogeneous polishing
pad has pores through which a fluid may flow.
69. The apparatus of claim 72, further comprising a platen
configured to support the polishing pad.
70. The apparatus of claim 69, wherein said platen comprises at
least one conduit and wherein a fluid is fed to said polishing
surface through said at least one conduit and said pores.
71. The apparatus of claim 60, wherein said homogeneous polishing
pad has an average wear rate in the range from less than 1
.mu.m/minute to about 10 .mu.m/minute.
Description
TECHNICAL FIELD
[0001] The present invention relates, generally, to the chemical
mechanical planarization of a workpiece and, more particularly, to
the chemical mechanical planarization of a workpiece using a
fixed-abrasive polishing pad.
BACKGROUND OF THE INVENTION
[0002] Chemical mechanical planarization ("CMP") is widely used in
the microelectronics industry, particularly for local and global
planarization of VLSI devices with sub-micron geometries. A typical
CMP process involves polishing back built-up layers of dielectrics
and conductors on integrated circuit chips during manufacture.
[0003] More particularly, a resinous polishing pad having a
cellular structure is traditionally employed in conjunction with a
slurry, for example, a water-based slurry comprising colloidal
silica particles. When pressure is applied between the polishing
pad and the workpiece (e.g., silicon wafer) being polished,
mechanical stresses are concentrated on the exposed edges of the
adjoining cells in the cellular pad. Abrasive particles within the
slurry concentrated on these edges tend to create zones of
localized stress at the workpiece in the vicinity of the exposed
edges of the polishing pad. This localized pressure creates
mechanical strain on the chemical bonds comprising the surface
being polished, rendering the chemical bonds more susceptible to
chemical attack or corrosion (e.g., stress corrosion).
Consequently, microscopic regions are removed from the surface
being polished, enhancing planarity of the polished surface. See,
for example, Arai et al., U.S. Pat. No. 5,099,614, issued March
1992; Karlsrud, U.S. Pat. No. 5,498,196, issued March 1996; Arai et
al., U.S. Pat. No. 4,805,348, issued February 1989; Karlsrud et
al., U.S. Pat. No. 5,329,732, issued July 1994; and Karlsrud et
al., U.S. Pat. No. 5,498,199, issued March 1996, for further
discussion of presently known lapping and planarization techniques.
By this reference, the entire disclosures of the foregoing patents
are hereby incorporated herein.
[0004] As the size of microelectronic structures used in integrated
circuits decreases to sub-half-micron levels, and as the number of
microelectronic structures on current and future generation
integrated circuits increases, the degree of planarity required
increases dramatically. The high degree of accuracy of current
lithographic techniques for smaller devices requires increasingly
flatter surfaces. However, presently known polishing techniques are
believed to be inadequate to produce the degree of local planarity
and global uniformity across the relatively large surfaces of
silicon wafers used in integrated circuits, particularly for future
generations.
[0005] In conventional CMP apparatus, the entire surfaces of the
polishing pads are used to planarize each workpiece, with the
result that initially the workpiece sees a totally fresh pad while
at the end of the process the workpiece sees a pad in glazed
condition. In addition, during polishing, the polishing pad wears
unevenly, developing worn and glazed tracks that result in
nonuniform polishing of the workpiece. In order to minimize these
problems, it is well known in the art to recondition the pad
between each workpiece, or a certain number of workpieces being
processed. However, adding the pad-reconditioning step to the
workpiece planarization process typically slows the throughput of
the apparatus. Also, while reconditioning the pad does assist in
making a glazed pad appear more like a fresh pad, the pad
nevertheless undergoes continuous mechanical and chemical
degradation through its life, introducing a variable that alters
the planarization process from workpiece to workpiece.
[0006] Another problem associated with present CMP systems relates
to the slurry delivery process. In conventional applications, the
slurry is introduced onto the abrading surface of the polishing
pad. However, the workpiece typically acts like a squeegee
preventing even distribution of the slurry across the workpiece. As
the polishing rate is related in part to the amount of slurry
beneath the workpiece during polishing, conventional slurry
delivery systems make uniform planarization processes
difficult.
[0007] CMP tools that use slowly advancing microabrasive sheets,
which do not necessarily require the use of slurries, are also
known in the art. While these tools do allow each workpiece to see
uniform pad conditions by slowly advancing the microabrasive sheet,
these tools introduce several new problems. For example, the known
tools do not adequately control the tension in the web resulting in
poor mechanical stability of the microabrasive sheet during the
planarization process of the workpiece. In addition, the
microabrasive particles and clusters may break off during
planarization processing, thereby resulting in pitting and
scratching of the workpiece.
[0008] Polishing pads formed of abrasive coatings on resilient
backings have been demonstrated to improve planarity. For an
example of abrasive coatings on resilent backings, see U.S. Pat.
No. 5,958,794, issued Sep. 28, 1999 to Bruxvoort et al.,
incorporated herein by reference Typically, polishing pads of this
nature are configured to be positioned proximate a subpad that is
situated between the polishing pad and the polishing station
platen. The subpad may comprise multiple layers, such as a
polycarbonate layer and a resilient foam layer, that attempt to
distribute load uniformly to the wafer. However, polishing pads
formed of abrasive coatings present a number of disadvantages. For
example, such pads are prone to defect generation similar to
abrasive sheets. In addition, to maintain the flexibility of the
pad, the abrasive coating is formed on a backing or substrate of
the pad in relatively thin layers, typically on the order of less
than 1 mm. However, with a thin abrasive coating, the polishing pad
is only able to polish a few wafers before the pad needs to be
replaced, thus decreasing wafer throughput and increasing costs.
Increasing the thickness of the coating does not address this
disadvantage, as not only is flexibility compromised but the
hardness of the coating increases dramatically as the thickness of
the abrasive coating increases. If the coating is too hard, it is
susceptible to fracturing, thus causing break off of particles and
clusters which pit and scratch the workpiece. Further, the hardness
of the abrasive coating adversely affects the load distribution on
the wafer.
[0009] A need therefore exists for an apparatus and method of
planarizing workpieces that enhance the planarization of the
workpieces while increasing wafer throughput. A need further exists
for an apparatus and method of planarizing workpieces that allow
each workpiece to experience similar pad conditions as all other
workpieces.
SUMMARY OF THE INVENTION
[0010] These and other aspects of the present invention will become
more apparent to those skilled in the art from the following
non-limiting detailed description of preferred embodiments of the
invention taken with reference to the accompanying figures.
[0011] In accordance with an exemplary embodiment of the present
invention, a homogeneous polishing pad for chemical mechanical
planarization of a workpiece has a thickness of at least about 1
millimeter. The polishing pad is friable and comprises an abrasive
material uniformly distributed throughout the pad which exhibits
abrasive behavior that does not degrade significantly as the pad
wears during planarization.
[0012] In accordance with another exemplary embodiment of the
present invention, the homogeneous polishing pad has at least one
channel through which a fluid may flow.
[0013] In accordance with a further exemplary embodiment of the
present invention, the homogeneous polishing pad has pores through
which a fluid may flow.
[0014] In accordance with yet a further exemplary embodiment of the
present invention, the homogeneous polishing pad has an average
wear rate in the range of from less than 1 .mu.m/minute to about 10
.mu.m/minute.
[0015] In accordance with another exemplary embodiment, a method of
chemical mechanical planarization of a workpiece includes providing
a homogeneous polishing pad having a thickness of at least about 1
millimeter. The polishing pad is friable and has abrasive material
uniformly distributed throughout. The abrasive material has
abrasive characteristics that do not degrade significantly as the
polishing pad wears during planarization. The method further
includes pressing the polishing pad against the workpiece while
causing relative motion between the polishing pad and the
workpiece.
[0016] In accordance with a further exemplary embodiment, an
apparatus for planarizing a workpiece includes a homogeneous
polishing pad having a thickness of at least about 1 millimeter.
The polishing pad is friable and has abrasive material uniformly
distributed throughout. The abrasive material has abrasive
characteristics that do not degrade significantly as the polishing
pad wears during planarization. A workpiece carrier is configured
to carry a workpiece and press the workpiece against the
homogeneous polishing pad.
[0017] In accordance with yet another exemplary embodiment, a
homogeneous polishing pad for chemical mechanical planarization of
a workpiece has an average wear rate in the range of from less than
1 .mu.m/minute to about 10 .mu.m/minute. The pad is friable and has
abrasive material uniformly distributed throughout the pad. The
abrasive material has abrasive characteristics that do not degrade
significantly as the pad wears during planarization.
[0018] In accordance with yet a further exemplary embodiment of the
present invention, an apparatus for planarizing a workpiece
includes a plurality of polishing stations. At least one of the
plurality of polishing stations has a homogeneous polishing pad
having a thickness of at least about 1 millimeter. The homogeneous
polishing pad is friable and has abrasive material uniformly
distributed throughout. The abrasive material has abrasive
characteristics that do not degrade significantly as the polishing
pad wears during planarization. A drive assembly is connected to at
least one of the plurality of polishing stations and is configured
to effect relative motion between the homogenous polishing pad and
the workpiece.
[0019] In accordance with another exemplary embodiment of the
present invention, an apparatus for planarizing a workpiece
includes a homogeneous polishing pad which is friable and has
abrasive material uniformly distributed throughout. The abrasive
material has abrasive characteristics that do not degrade
significantly as the homogeneous polishing pad wears during
planarization. A drive assembly is configured to move the polishing
pad in an orbital pattern. A workpiece carrier is configured to
carry a workpiece and press the workpiece against the homogeneous
polishing pad.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0020] Exemplary embodiments of the present invention will
hereafter be described in conjunction with the appended drawing
figures, wherein like designations denote like elements, and:
[0021] FIG. 1 is a side cross-sectional view of an exemplary
embodiment of the fixed-abrasive polishing station of the present
invention;
[0022] FIG. 2 is a top view of an exemplary embodiment of a platen
of the fixed-abrasive polishing station of the present
invention;
[0023] FIG. 3 is a top view of an exemplary embodiment of a
fixed-abrasive polishing pad of the present invention;
[0024] FIG. 4 is a top view of another exemplary embodiment of a
fixed-abrasive polishing station of the present invention; and
[0025] FIG. 5 is a top view illustration of an exemplary embodiment
of a CMP apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The following description is of exemplary embodiments only
and is not intended to limit the scope, applicability or
configuration of the invention in any way. Rather, the following
description provides a convenient illustration for implementing
exemplary embodiments of the invention. Various changes to the
described embodiments may be made in the function and arrangement
of the elements described without departing from the scope of the
invention as set forth.
[0027] A schematic representation of an exemplary embodiment of a
polishing station 10 of the present invention is shown in FIG. 1.
Polishing station 10 includes a polishing platen 12 mounted for
motion by a drive motor (not shown). A thick fixed-abrasive
polishing pad 14 with a polishing surface 16 is mounted to
polishing platen 12.
[0028] Fixed-abrasive polishing pad 14 has a generally homogenous
composition with a suitably rigid constitution which permits pad 14
to have a thickness greater than 1 mm, preferably having a
thickness in the range of from about 0.5 inches to 1.5 inches and
more preferably having a thickness of about 1 inch. While pad 14 is
relatively thick compared to prior art abrasive coated pads, it has
a suitable hardness that enhances uniform planarization. The pad 14
is configured to have a relatively continuous wear rate throughout
the life of the pad. Thus, as planarization proceeds, a fresh
abrasive surface is continuously exposed to the wafer. Preferably,
pad 14 has an average wear rate in the range of from less than 1
.mu.m/min to about 10 .mu.m/min as measured over the life of the
pad. Thus, for a pad 14 having a thickness of 1 inch, 10,000 wafers
or more could be planarized before the polishing pad would require
replacement.
[0029] Fixed-abrasive polishing pad 14 may be formed from
resin-bonded material with fixed abrasives uniformly distributed
throughout. Fixed abrasives may include cerium oxide, aluminum
oxide, silicon dioxide or any other abrasives suitable for
planarizing a workpiece. Alternatively, fixed-abrasive polishing
pad 14 may be formed from a ceramic-bonded material. The
ceramic-bonded material may be of a soft porous type which may be
strengthened by a stiffening agent such as melamine. Fixed abrasive
polishing pad 14 may be of an open-cell or closed-cell structure
and may be formed by suitable molding, firing and machining
methods.
[0030] In addition, fixed-abrasive polishing pad 14 may exhibit
friable behavior. As abrasive particles of friable materials dull,
the coefficient of friction between the abrasive particles and the
workpiece increase. At a critical point, the shear stresses at the
points of contact will be greater than the bond strength of the
abrasive particles to the pad. This will cause the more dull
particles to break away from the pad, creating fresh, sharp points.
With such a self-sharpening fixed abrasive polishing pad 14, the
workpiece can be polished efficiently, with an increased polishing
life compared to conventional pads.
[0031] During planarization, workpiece W is held by a workpiece
carrier 18, which urges a workpiece W against fixed-abrasive
polishing pad 14 with a desired amount of force. Workpiece W may be
rotated by workpiece carrier 18 about an axis 20. Alternatively,
workpiece carrier 18 may move workpiece W in an orbital pattern.
Workpiece carrier 18 has a workpiece head 34. The purpose of
workpiece head 34 is to help secure workpiece W to workpiece
carrier 18 and also to prevent the workpiece from becoming
dislodged during planarization. Any of a number of different types
of workpiece heads can be used. For examples of suitable workpiece
heads, see the following patents, incorporated herein by this
reference: U.S. Pat. No. 6,056,632, issued May 2, 2000 to Mitchel
et al.; U.S. Pat. No. 5,989,104, issued Nov. 23, 1999 to Kim et
al.; U.S. Pat. No. 6,024,630, issued Feb. 15, 2000 to Shendon et
al.; U.S. Pat. No. 5,762,544, issued Jun. 9, 1998 to Zuniga et al.;
U.S. Pat. No. 6,080,050, issued Jun. 27, 2000 to Chen et al.; and
U.S. Pat. No. 5,738,574, issued Apr. 14, 1998 to Tolles et al.
[0032] Workpiece carrier 18 may advance the workpiece toward
polishing station 10 and apply pressure such that the workpiece
engages the polishing surface 16 of the fixed-abrasive polishing
pad 14 with a desired amount of force by a variety of mechanisms,
for example, by expansion of a membrane assembly integral with the
workpiece head 34, as more fully disclosed in U.S. Pat. No.
6,056,632. Workpiece carrier 18 also may be operatively connected
to a pneumatic assembly (not shown) which moves a shaft 36
vertically, thus advancing the workpiece vertically down toward
polishing pad 14 for polishing and moving the workpiece vertically
up after polishing.
[0033] While workpiece carrier 18 urges workpiece W against
polishing pad 14, polishing station 10 uses relative motion,
preferably orbital motion, to polish workpiece W. In an exemplary
embodiment, two rotatable shafts 22 and 24 are off-set from each
other by the amount of a desired orbit. The radius of the orbit is
preferably less than the radius of the workpiece W. Shaft 22 may
rotate in the direction indicated by arrow A26 and shaft 24 may
rotate at the same speed, but in the direction indicated by arrow
A28. Eccentrics or cams (not shown) may be coupled to shaft 24 to
allow polishing station 10 to also dither (in one or more axes as
indicated by arrows A30 and A32). An example of polishing a
workpiece by orbital motion is disclosed in U.S. Pat. No.
5,554,064, issued Sep. 10, 1996 to Breivogel et al., which patent
is incorporated herein by reference. It is to be appreciated that a
variety of other well-known means may be employed to facilitate the
orbital motion of the polishing station 10 in the present
invention. Alternatively, polishing station 10 may be rotated about
a central axis by the drive motor.
[0034] An advantage of fixed-abrasive polishing pad 14 is that, as
it wears, it continues to exhibit fresh mechanical and chemical
abrasive qualities. Fixed-abrasive polishing pad 14 is also less
susceptible to wear than conventional polishing pads. Accordingly,
the wear rate and nonuniformity of wear is significantly less for
pad 14 than for conventional polishing pads. Thus, pad 14 is able
to uniformly planarize a greater number of workpieces than
conventional pads. Increasing the thickness of fixed-abrasive
polishing pad 14, preferably in the range of from about 0.5 inches
to about 1.5 inches, and more preferably to about one inch, may
further increase the number of workpieces that can be planarized
before pad 14 needs to be replaced. To further maintain the uniform
mechanical characteristics of pad 14, it may also be desirable to
recondition surface 16 of pad 14, for example, by passing a diamond
dressing plate over surface 16, as is know in the art.
[0035] To reduce heat generated by the planarization process and
enhance uniformity of planarization, a fluid may be delivered to
surface 16 of pad 14 by a manifold apparatus 38, as illustrated in
FIGS. 1 and 2. The fluid may include any suitable liquid, such as
deionized water, surfactants, lubricants or a slurry or a
combination thereof. The fluid may be chemically treated to
increase or decrease the mechanical action between pad 14 and the
workpiece, such as to reduce wear of polishing pad 14 or reduce
scratching of the workpiece. Alternatively, the pH and ionic
composition may be suitably adjusted to enhance or reduce the
chemical reaction between pad 14 and the workpiece. A pump 40 may
distribute the fluid through a fluid line 52 and through
distribution manifold 38 in the direction indicated by arrow A42 to
one or more conduits 44 formed within platen 12. Conduits 44 allow
for easy transportation of the fluid through platen 12. Fluid may
then suitably flow from conduits 44 through one or more bores 48 in
the direction of arrows A46. in contrast to conventional rotating
polishing stations, an orbiting polishing station typically
provides the advantage that fluid may be supplied through the
polishing station to the polishing surface without the use of
rotary unions or the like. However, it is to be appreciated that
manifold apparatus 38 may be employed by a rotating polishing
station utilizing the appropriate rotary unions, rotary couplings
and the like.
[0036] Referring to FIGS. 1 and 3, fixed-abrasive polishing pad 14
similarly has one or more channels 50, which permit fluid to flow
from bores 48 of platen 12 to the pad surface. Channels 50 may be
molded into pad 14 when originally fabricated or may be machined
into pad 14. Through bores 48 and channels 50, the fluid may flow
from conduits 44 to the surface 16 of pad 14. In another
embodiment, polishing pad 14 may have trenches 54, which extend
between channels 50 on surface 16. The fluid may flow through the
trenches 54 for even distribution below workpiece W.
[0037] In an alternative embodiment, fixed abrasive polishing pad
may be of an open-cell structure having pores. Fluid may be
delivered from manifold apparatus 38 to surface 16 of pad 14
through the pores of pad 14. Alternatively, fluid may be delivered
to the polishing pad by way of a conventional conduit which
delivers the fluid directly to the top surface of the polishing
pad.
[0038] While polishing station 10 is illustrated in FIGS. 2 and 3
as round in shape, alternatively, polishing station 10 may be of
any suitable shape, such as square or rectangular as shown in FIG.
4.
[0039] The fixed-abrasive polishing station of the present
invention may be used in a variety of CMP apparatus. For example,
the fixed-abrasive polishing pad of the present invention may be
used in an integrated, multiple polishing station system, such as
the Avantgaard.TM. 776, Momentum.TM. and Genesis.TM. CMP Systems by
Speedfam-IPEC. Such multiple polishing station systems may have two
or more polishing stations for performing CMP on workpieces.
Referring to FIG. 5, a multiple polishing stations apparatus 100 is
illustrated having four polishing stations 102, 104, 106, and 108,
although it will be appreciated that multiple polishing stations
apparatus 100 may have one, two or any other suitable number of
polishing stations. Polishing stations 102, 104, 106 and 108 each
may be fixed-abrasive polishing stations, according to the present
invention, that are configured to move orbitally.
[0040] Fixed-abrasive polishing stations 102, 104, 106 and 108 are
positioned within a base 110 having a top surface 112. Top surface
112 is configured with a number of openings 114 to correspond to
the number of polishing stations employed by multiple polishing
station apparatus 100. Openings 114 are large enough to permit the
fixed abrasive polishing stations to orbit without interference
from base 110. A workpiece handling robot 116 is centered between
the polishing stations and is configured to transport a workpiece
from a transfer station 118 to one of the polishing stations for
polishing and back to the transfer station after polishing.
[0041] Multiple polishing stations apparatus 100 employs workpiece
carriers (not shown), the number of which may correspond to the
number of polishing stations. The workpiece carriers receive
workpieces from the workpiece handling robot 116 and hold the
workpieces and polish them by pressing them against the respective
fixed-abrasive polishing stations 102, 104, 106 and 108. Each of
the workpiece carriers aligns vertically with a corresponding
polishing station and is attached to the end of a cylindrical shaft
that is configured to rotate the workpiece carrier and the
workpiece around a longitudinal axis of the shaft. In addition to
rotation about the longitudinal axis, the workpiece carrier may be
configured to translate radially or otherwise oscillate or dither.
Alternatively, the workpiece carriers may be suitably configured to
move orbitally so that during polishing the workpiece carrier and
the fixed-abrasive polishing station both move orbitally,
preferably in opposite directions.
[0042] During operation of multiple polishing station apparatus
100, robot 116 receives a workpiece W from transfer station 118.
Robot 116 then positions workpiece W proximate to one of the
polishing stations 102, 104, 106 or 108. A workpiece carrier
aligned vertically about the respective polishing station receives
a workpiece W from robot 116. The workpiece carrier then urges
workpiece W against a fixed-abrasive polishing pad 120 of the
fixed-abrasive polishing station. The workpiece carrier presses
workpiece W against the fixed-abrasive polishing pad 120 as it
rotates or, alternatively, orbits. The fixed-abrasive polishing
station preferably orbits, as described above, to uniformly
planarize and polish W, although it will be appreciated that the
fixed-abrasive polishing station may rotate, as opposed to orbit,
or move in a combined orbital and rotational manner.
[0043] After polishing of workpiece W, the workpiece carrier raises
workpiece W above the fixed-abrasive polishing station. Robot 116
then moves into a suitable position to receive workpiece W from the
workpiece carrier. Robot 116 then may transport workpiece W to a
buffing station 122 for buffing of workpiece W. After buffing of
workpiece W, robot 116 removes workpiece W from buffing station 122
and back to transfer station 118. After polishing, the
fixed-abrasive polishing pad may be reconditioned. Alternatively,
the fixed abrasive polishing pad may be reconditioned during
polishing of the workpiece.
[0044] While multiple polishing station apparatus 100 is
illustrated in FIG. 5 with all polishing stations 102, 104, 106 and
108 employing fixed-abrasive polishing stations, it will be
appreciated that in an alternative embodiment only one of the
multiple stations may employ a fixed-abrasive polishing station,
with the other polishing stations employing any suitable polishing
apparatus. For example, in one embodiment of the multiple polishing
station 100, only one fixed-abrasive polishing station may be
employed, while the other polishing stations employ conventional
rotating polishing platens using conventional CMP polishing pads.
Accordingly, workpiece W may be polished first at the
fixed-abrasive polishing station and subsequently at a conventional
CMP rotating or orbiting platen. In another embodiment, on orbital
fixed-abrasive polishing station may be employed while the other
fixed-abrasive polishing stations do not orbit.
[0045] Alternatively, the fixed abrasive polishing pad of the
present invention may also be used in other multiple polishing
station systems. For example, the fixed abrasive polishing pad of
the present invention may be used in one or more polishing stations
of a carousel-type CMP apparatus. For examples of carousel-type CMP
apparatuses, see U.S. Pat. No. 5,804,507, issued Sep. 8, 1998 to
Perlov et al. and U.S. Pat. No. 5,738,574, issued Apr. 14, 1998 to
Tolles et al., which are incorporated herein by this reference.
[0046] Although the subject invention has been described herein in
conjunction with the appended drawing Figures, it will be
appreciated that the scope of the invention is not so limited.
Various modifications in the arrangement of the components
discussed and the steps described herein for using the subject
device may be made without departing from the spirit and scope of
the invention as set forth in the appended claims.
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