U.S. patent application number 10/724350 was filed with the patent office on 2005-06-02 for integrated pad and belt for chemical mechanical polishing.
This patent application is currently assigned to Lam Research Corporation. Invention is credited to Chadda, Saket, Jairath, Rahul, Krusell, Wilbur C., Mishra, Kamal, Pant, Anil K..
Application Number | 20050118936 10/724350 |
Document ID | / |
Family ID | 25178228 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050118936 |
Kind Code |
A1 |
Pant, Anil K. ; et
al. |
June 2, 2005 |
Integrated pad and belt for chemical mechanical polishing
Abstract
An integrated pad and belt for polishing a surface comprising a
belt integrated with a polishing pad that forms a seamless
polishing surface.
Inventors: |
Pant, Anil K.; (Santa Cruz,
CA) ; Jairath, Rahul; (San Jose, CA) ; Mishra,
Kamal; (San Jose, CA) ; Chadda, Saket; (San
Jose, CA) ; Krusell, Wilbur C.; (Palo Alto,
CA) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Lam Research Corporation
|
Family ID: |
25178228 |
Appl. No.: |
10/724350 |
Filed: |
November 26, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10724350 |
Nov 26, 2003 |
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09957433 |
Sep 20, 2001 |
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6656025 |
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09957433 |
Sep 20, 2001 |
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08800373 |
Feb 14, 1997 |
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6328642 |
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Current U.S.
Class: |
451/56 |
Current CPC
Class: |
B24B 21/04 20130101;
B24D 11/06 20130101; B24B 37/04 20130101; B24D 11/00 20130101 |
Class at
Publication: |
451/056 |
International
Class: |
B24B 001/00 |
Claims
We claim:
1. A method of integrating a polishing pad with a belt to form an
integrated pad and belt for polishing a surface, comprising the
following steps: forming a belt; and integrating said belt with a
polishing pad formed during said integrating step to form an
integrated pad and belt, said integrated pad and belt comprises a
polishing surface.
2. The method of claim 1 wherein said polishing surface of said
integrated pad and belt comprises a seamless polishing surface.
3. The method of claim 1 wherein said polishing pad of said
integrated pad and belt comprises a polymeric material.
4. The method of claim 1 wherein said step of integrating said
polishing pad with said belt comprises molding said polishing pad
onto said belt that produces a seamless surface on said integrated
pad and belt.
5. The method of claim 1 wherein said belt of said integrated pad
and belt comprises one or more of an aramid, cotton, metal, metal
alloy, or polymeric material.
6. The method of claim 1 wherein said belt of said integrated pad
and belt comprises a tensile material and a reinforcing
material.
7. The method of claim 1 wherein said tensile material further
comprises an aramid material and said reinforcing material further
comprises a cotton material.
8. A method of forming an integrated pad and belt for use in
polishing a semiconductor wafer, the method comprising: weaving a
first and a second material into an endless belt; and molding a
semiconductor wafer polishing pad material onto the endless belt in
a seamless manner and integrating the semiconductor wafer polishing
pad material and endless belt in a single step.
9. The method of claim 8, wherein the first material comprises an
aramid fiber.
10. The method of claim 9, wherein the second material comprises a
cotton fiber.
11. The method of claim 8, wherein the step of molding the
semiconductor wafer polishing pad material comprises molding the
semiconductor wafer polishing pad material onto the endless belt
using an adhesive molding process.
12. The method of claim 8, wherein the semiconductor wafer
polishing pad material comprises a polymeric material.
13. The method of claim 12, wherein the polymeric material
comprises polyurethane.
14. The method of claim 8, wherein the step of weaving the first
and second materials comprises weaving the first material in an
intended direction of linear motion for the endless belt and
weaving the second material in an angularly offset direction from
the intended direction of linear motion.
15. A method of forming an integrated pad and belt for use in
polishing a semiconductor wafer, the method comprising: forming a
belt; and extruding a semiconductor wafer polishing pad material
onto the belt and integrating the semiconductor wafer polishing pad
material with the belt in a single step to form the integrated pad
and belt.
16. The method of claim 15, wherein forming the belt comprises
joining opposite ends of a material to form an endless loop and
wherein the material comprises at least one of metal, aramid
material, cotton and polymeric material.
17. The method of claim 15, wherein forming the belt comprises
weaving an aramid fiber in a direction of intended linear movement
of the belt and a cotton material in a direction at an angle to the
direction of intended linear movement to form a rectangular piece
and weaving together two ends of the rectangular piece to form an
endless loop.
18. The method of claim 15, wherein forming a belt comprises
forming a belt having a thickness in a range of 0.01 inches to 0.2
inches.
19. The method of claim 18, wherein a polishing surface of the
semiconductor wafer polishing material is formed with a plurality
of indentations.
20. The method of claim 19, wherein the step of extruding the
semiconductor wafer polishing pad material comprises forming the
polishing surface in a seamless manner and eliminating propagation
of any defects in the belt through to the polishing surface.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 09/957,433, filed Sep. 20, 2001, pending, which is a division
of U.S. application Ser. No. 08/800,373, filed Feb. 14, 1997, now
U.S. Pat. No. 6,328,642, and the entire disclosure of each of these
references is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of semiconductor
wafer processing and, more particularly, to chemical-mechanical
polishing of semiconductor wafers using a linear polisher.
DESCRIPTION OF THE RELATED ART
[0003] The manufacture of an integrated circuit device requires the
formation of various layers (both conductive and non-conductive)
above a base substrate to form the necessary components and
interconnects. During the manufacturing process, removal of a
certain layer or portions of a layer must be achieved in order to
pattern and form various components and interconnects. Chemical
mechanical polishing (CMP) is being extensively pursued to
planarize a surface of a semiconductor wafer, such as a silicon
wafer, at various stages of integrated circuit processing. Other
examples of CMP include flattening optical surfaces, metrology
samples, and various metal and semiconductor based substrates.
[0004] CMP is a technique in which a chemical slurry is used along
with a polishing pad to polish away materials on a semiconductor
wafer. The mechanical movement of the pad relative to the wafer in
combination with the chemical reaction of the slurry disposed
between the wafer and the pad, provide the abrasive force with
chemical erosion to polish the exposed surface of the wafer (or a
layer formed on the wafer), when subjected to a force pressing the
wafer to the pad. In the most common method of performing CMP, a
substrate is mounted on a polishing head which rotates against a
polishing pad placed on a rotating table (see, for example, U.S.
Pat. No. 5,329,732). The mechanical force for polishing is derived
from the rotating table speed and the downward force on the head.
The chemical slurry is constantly transferred under the polishing
head. Rotation of the polishing head helps in the slurry delivery
as well in averaging the polishing rates across the substrate
surface.
[0005] One technique for obtaining a more uniform chemical
mechanical polishing rate is to utilize a linear polisher. Instead
of a rotating pad, a moving belt is used to linearly move the pad
across the wafer surface. The wafer is still rotated for averaging
out the local variations, but the global planarity is improved over
CMP tools using rotating pads. One such example of a linear
polisher is described in a pending application titled "Linear
Polisher And Method For Semiconductor Wafer Planarization;" Ser.
No. 08/287,658; filed Aug. 9, 1994. Unlike the hardened table top
of a rotating polisher, linear polishers are capable of using
flexible belts with separate pads disposed on the belts. This
flexibility allows the belt to flex and change the pad pressure
being exerted on the wafer.
[0006] A linear polishing tool generally has two separate
consumables, a pad and a belt. The life span of a pad is short due
to its use as the contact surface for polishing a semiconductor
wafer and the need for conditioning the pad's surface during or
between each polishing run. Although not replaced with the
frequency of the pad, the belt also needs periodic replacement
resulting from several causes including wear from the high
operating speeds of the polisher, the heavy loads exerted on the
belt during the polishing, and deformation or kinks due to
accidents when replacing the polishing pads. The prior practice is
to use separate polishing pads attached to stainless steel belts
with an adhesive.
[0007] There are several disadvantages to using separate pads and
belts with linear polishing tools. One disadvantage is that
changing pads and or belts is both time consuming and costly. The
mere act of replacing a pad and or a belt incurs a significant
amount of time for labor. It typically takes about 15 to 20 minutes
to install new pad strips on a belt, while the removal process of
the old pad strips typically takes about 15 to 20 minutes. The cost
associated with replacing belts and pads lies in the downtime
associated with the their replacement. In the semiconductor
industry, as with many industries, time is money. A linear
polishing tool generally polishes one wafer every 2 to 3 minutes.
Each additional or unnecessary minute spent replacing a pad and or
a belt is lost revenue.
[0008] A pad (on a belt) generally consists of one or more strips
of pad material with each strip being approximately equal to the
belt width. One current example of a pad strip has a width of about
12 to 14 inches and a length of about 36 inches. The pad strips are
put on the belt one at a time and must be carefully aligned to the
belt and to each other. A very strong adhesive attaches the pad
strips to the belt in such a way as to minimize and avoid the
formation of air bubbles, which causes the pad strips to eventually
separate from the belt.
[0009] When a pad wears out, it is necessary to replace all of the
pad strips. The strips are removed from the belt by physically
pulling or ripping them off of the belt. After removing the strips,
it is necessary to remove the old adhesive from the belt. Removing
the old adhesive usually requires using an organic solvent such as
acetone or isopropyl alcohol. Great care is necessary during the
removal process so as not to damage the belt since the belt by
itself is typically only 0.02 inches thick.
[0010] Another disadvantage of the prior practice is the presence
of one or more "seams" in the contact or polishing surface. A steel
belt invariably has a noticeable welding seam that propagates
through the pad to the polishing surface of the pad. The typical
practice in manufacturing the belt is to take a rectangular piece
of stainless steel and weld the ends together to form the stainless
steel belt. The weld is then ground to smooth out the welded
surface. Even with grinding the seam, there will still be some type
of irregularity on the surface of the steel belt. After attaching
the pad strips to the belt, this irregularity usually propagates
through the pad so that the polishing surface of the pad will also
have some irregularity or unevenness. Additional seams or
irregularities on the polishing surface of the pad are produced
when securing the pads to the belt. As previously noted, the
typical practice is for the pads to be in rectangular strips before
attachment to the belt. Another seam or some type of unevenness in
the outer surface of the pad appears at the joinder of the two ends
of the pad. Due to the small geometries required in semiconductor
devices, any irregularities, unevenness, or seams on the pad's
polishing surface will produce an uneven planarization on the
surface of the semiconductor device.
[0011] The present invention describes an integrated pad and belt
for polishing a surface such as glass or a semiconductor wafer. The
integration of the pad with the belt reduces the down time of the
linear polisher because there is only one piece to replace as
opposed to the two pieces with the current practice. The
manufacture of the integrated pad and belt allows a belt to be
constructed without a noticeable welding seam, which reduces
unevenness or irregularities on the polishing surface of the pad.
Further, the integrating of the pad with the belt produces a
seamless polishing surface, which further reduces the unevenness of
the polishing surface of the pad. Still further, an integrated pad
and belt eliminates trapped air bubbles between separate pads and
belts resulting from replacing the pads. The present invention,
therefore, reduces the number of defects by promoting a better
polishing uniformity, and improves reliability by reducing the
number of steps required to replace pads and belts, while at the
same time, decreasing the down time of the linear polishing
tool.
SUMMARY OF THE INVENTION
[0012] The present invention describes an integrated pad and belt
for polishing a surface. The integrated pad and belt comprises a
polishing pad integrated with a belt that forms a seamless
polishing surface. The polishing pad component of the integrated
pad and belt comprises a polymeric material. The belt component of
the integrated pad and belt may comprise one or more of an aramid,
cotton, metal, metal alloy, or polymeric material. An alternative
embodiment of the present invention is a linear polishing tool
comprising the above integrated pad and belt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a pictorial illustration of a linear polishing
tool.
[0014] FIG. 2 is a cross-sectional diagram of the linear polishing
tool of FIG. 1.
[0015] FIG. 3 is a cross sectional diagram of an integrated pad and
belt for practicing the present invention.
[0016] FIGS. 4A and 4B illustrate different embodiments for the
weaving of fibers for a belt component of the integrated pad and
belt of the present invention.
[0017] FIG. 5 is a pictorial illustration of an integrated pad and
belt with a linear polishing tool for practicing the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] This disclosure describes an integrated pad and belt for
polishing a surface comprising a belt integrated with a polishing
pad that forms a seamless polishing surface. The following
description sets out numerous specific details such as specific
structures, materials, polishing techniques, etc., to provide a
thorough understanding of the present invention. However, one
skilled in the art will appreciate that they may practice the
present invention without these specific details. In other
instances, this description does not describe well known techniques
and structures in detail in order not to obscure the present
invention. This disclosure describes the preferred embodiment of
the present invention in reference to a linear polishing tool,
however, the invention can be readily adapted to other polishing
techniques, such as a rotating disk polishing tool. Although this
disclosure describes the present invention in reference to
performing CMP on a semiconductor wafer, the present invention is
readily adaptable to polish other materials such as glass or
substrates for the manufacture of flat panel displays.
[0019] FIGS. 1 and 2 show a linear polishing tool 10 in current
practice. The linear polishing tool 10 polishes away materials on
the surface of a semiconductor wafer 11. The material being removed
can be the substrate material of the wafer itself or one of the
layers formed on the substrate. Such formed layers include
dielectric materials (such as silicon dioxide or silicon nitride),
metals (such as aluminum, copper or tungsten), metal alloys or
semiconductor materials (such as silicon or polysilicon). More
specifically, a polishing technique generally known in the art as
chemical-mechanical polishing (CMP) is employed to polish one or
more of these layers fabricated on the wafer 11, in order to
planarize the surface layer. Generally, the art of performing CMP
to polish away layers on a wafer is known and prevalent practice
has been to perform CMP by subjecting the surface of the wafer to a
rotating platform (or platen) containing a pad (see for example,
the Background section above). An example of such a device is
illustrated in U.S. Pat. No. 5,329,732.
[0020] The linear polishing tool 10 utilizes a stainless steel belt
12 in the prior art, which moves linearly in respect to the surface
of the wafer 11. The belt 12 is a continuous belt rotating about
rollers (or spindles) 13 and 14. The rollers are driven by a
driving means, such as a motor, so that the rotational motion of
the rollers 13-14 causes the belt 12 to be driven in a linear
motion with respect to the wafer 11, as shown by arrow 16. A
polishing pad 15 in the prior art affixes onto belt 12 at its outer
surface facing wafer 11 so that pad 15 moves linearly relative to
wafer 11 as belt 12 is driven. The present invention describes an
integrated pad and belt, which is an improvement over and a
replacement for the separate pad and belt shown in the prior
art.
[0021] The wafer 11 is made to reside within a wafer carrier 17,
which is part of a housing 18. The wafer 11 is held in position by
a mechanical retaining means (such as a retainer ring) and/or by
vacuum. The wafer carrier 17 positions the wafer atop belt 12 so
that the surface of the wafer comes in contact with pad 15. It is
preferred to rotate the housing 18 in order to rotate the wafer 11.
The rotation of the wafer 11 allows for averaging of the polishing
contact of the wafer surface with 15. An example of a linear
polishing tool is described in the previously mentioned pending
patent application titled "Linear Polisher And Method For
Semiconductor Wafer Planarization."
[0022] The linear polishing tool 10 additionally contains a slurry
dispensing mechanism 20, which dispenses a slurry 21 onto pad 15.
The slurry 21 is necessary for proper CMP of the wafer 11. A pad
conditioner (not shown in the drawings) is typically used in order
to recondition the pad during use. Techniques for reconditioning
the pad during use are known in the art and generally require a
constant scratching or grooving of the pad in order to remove the
residue build-up caused by the used slurry and removed waste
material. One of a variety of pad conditioning or pad cleaning
devices can be readily adapted for use with linear polisher 10.
[0023] The linear polishing tool 10 also includes a platen 25
disposed on the underside of belt 12 and opposite from carrier 17,
such that belt 12 resides between platen 25 and wafer 11. A primary
purpose of platen 25 is to provide a supporting platform on the
underside of belt 12 to ensure that the polishing surface of pad 15
makes sufficient contact with wafer 11 for uniform polishing.
Typically, the carrier 17 is pressed downward against belt 12 and
pad 15 with appropriate force, so that wafer 11 makes sufficient
contact with the contact surface of pad 15 for performing CMP.
Since the belt 12 is flexible and will depress when the wafer is
pressed downward onto the pad 15, platen 25 provides a necessary
counteracting force to this downward force.
[0024] Although platen 25 can be of a solid platform, a preference
is to have platen 25 function as a type of fluid bearing for the
practice of the present invention. One example of a fluid bearing
is described in a pending U.S. Pat. No. application titled "Wafer
Polishing Machine With Fluid Bearings;" Ser. No. 08/333,463; filed
Nov. 2, 1994, which describes fluid bearings having pressurized
fluid directed against the polishing pad.
[0025] The present invention describes an integrated pad and belt,
which is an improvement over and a replacement for the separate pad
and belt shown in the current practice of FIGS. 1 and 2. FIG. 3 is
a cross sectional diagram of an integrated pad and belt 31 for
practicing the present invention. The integrated pad and belt
comprises a belt 30 integrated with a polishing pad 34 that forms a
seamless polishing surface 33. The seamless polishing surface is a
feature of the present invention, as previously stated, that
eliminates pad to pad seams resulting from the joinder of pads and
seams on the belt, due to it's manufacture, that propagate through
the pad to appear on the polishing surface. Although the polishing
surface 33 does not have seams, the polishing surface typically,
although not required, has grooves, pits, or other similar types of
indentions on the polishing surface to aid in the channeling of the
polishing slurry and waste material. The preferred embodiment of
the pad component of the integrated pad and belt uses grooves
oriented in the direction of linear motion as a form of indention
on it's polishing surface.
[0026] FIG. 4A and FIG. 4B illustrate a belt component 30 of the
integrated pad and belt in FIG. 3. The belt component 30 of the
preferred embodiment comprises weaved tensile material or fibers 36
and reinforcing material or fibers 38. The preferred embodiment of
present invention uses aramid fibers for the tensile fibers and
cotton fibers for the reinforcing fibers, where the aramid fibers
further comprise KEVLAR.TM. aramid fibers. The weaving of the belt
component 30 places the aramid fibers 36 in the direction of linear
motion 16 of the linear polishing tool 10 of FIGS. 1 and 2 with the
reinforcing cotton fibers 38 offset angularly from the aramid
fibers. The belt component provides the integrated pad and belt
with a high tensile strength necessary to withstand the downward
force exerted by the wafer carrier 17 of FIG. 2, a pressure that in
current practice comprises a force of 3000 pounds of pressure. An
additional benefit of the aramid fibers in the belt component is
they are not reactive to the chemicals used in CMP. Although the
preferred embodiment of the present invention uses aramid and
cotton fibers for the belt component of the integrated pad and
belt, other types of materials are also suitable for use in the
belt component that includes metals such as stainless steel, metal
alloys, or a polymeric material. Additionally, one skilled in the
art will appreciate that reinforcing fibers provide reinforcement
to the tensile fibers when offset at some angle. The degree of
reinforcement is dependent upon the offset angle and the nature of
the weave, e.g., one can have reinforcement material at different
offsets from the tensile material. FIG. 4A illustrates the
reinforcement material at an orthogonal angle to the tensile
material, and FIG. 4B illustrates the reinforcement material at an
offset angle to the tensile material.
[0027] The preferred thickness of the belt component comprises a
thickness between 0.010 inches and 0.200 inches, with the preferred
embodiment having a thickness of approximately 0.025 inches.
Although this disclosure describes a range of thicknesses, one
skilled in the art will appreciate that other thicknesses of the
belt component are possible.
[0028] Even though the belt component is originally manufactured in
a rectangular piece, the fibrous nature of the belt component
allows the two ends of the rectangular piece to be weaved together
to form an endless belt. The weaving of the two ends produces a
belt component with virtually no noticeable seam, which is in stark
contrast to the welding and grinding of current practice with
stainless steel belts.
[0029] FIG. 5 is a pictorial illustration of an integrated pad and
belt 31 with the linear polishing tool of FIGS. 1 and 2. FIG. 5
illustrates the integrated pad and belt replacing the separate pad
and belt shown in the current practice. The pad component 34 of the
integrated pad and belt comprises a polymeric material and provides
a seamless polishing surface 33 for wafer 11. Although the
preferred embodiment of the present invention uses a polymeric
material for the pad component of the integrated pad and belt,
other types of polymeric materials such as polyester or
polyurethane are also suitable for use in the pad component.
[0030] The thickness of the pad component of the integrated pad and
belt helps in achieving an even planarization of the wafer with the
linear polishing tool. Additionally, the thickness of the pad
component in combination with the material used in the pad
component determines the durability or life time of the pad. The
preferred thickness of the pad component comprises a thickness
between 0.010 inches and 0.250 inches, with the preferred
embodiment having a thickness of approximately 0.100 inches.
Although this disclosure describes a range of thicknesses, one
skilled in the art will appreciate that other thicknesses of the
pad component are possible.
[0031] An integration process integrates the pad component 34 with
the belt component 30 to form the integrated pad and belt. The
preferred integration process, a molding process, forms and
integrates the pad component in a single step. Additionally, the
integration process helps in the formation of a seamless polishing
surface 33 on the integrated pad and belt 31 by firmly integrating
the two components together so that the integrated unit is able to
withstand the high linear speeds necessary for CMP with a linear
polishing tool. Further, the integration process effectively fills
in any irregularities or unevenness that may occur in the belt
component so that any defects do not propagate through to the
seamless polishing surface. An alternative embodiment of the
present invention integrates another pad component on the underside
of the belt component 30. Although the preferred embodiment of the
present invention uses a molding process for the integration
process, other types integration processes are also suitable for
integrating the pad component with the belt component including
extrusion processes or adhesive molding processes.
[0032] FIG. 5 additionally describes another embodiment of the
present invention that comprises the linear polisher 10 of FIGS. 1
and 2 and the integrated pad and belt 31.
[0033] The present invention describes an integrated pad and belt
for polishing a surface. The integrated pad and belt comprises a
polishing pad integrated with a belt that forms a seamless
polishing surface. An alternative embodiment of the present
invention is a linear polishing tool comprising the above
integrated pad and belt. An advantage of integrating a polishing
pad with a belt is that the integrated unit reduces the down time
of the linear polishing tool because there is only one piece to
replace as opposed to the two pieces with the current practice.
Another advantage of an integrated pad and belt is that it
eliminates trapped air bubbles between separate pads and belts
resulting from replacing the pads. Yet another advantage is that
the integration of the polishing pad with the belt allows one to
manufacture an integrated unit with a seamless polishing surface. A
seamless polishing surface promotes an even planarization of the
wafer. Together, these advantages reduce the number of defects in
the wafer by promoting a better polishing uniformity and more even
planarization, and improves reliability by reducing the number of
steps and the time required to replace separate pads and belts, and
at the same time decreasing the down time of the linear polishing
tool.
* * * * *