U.S. patent application number 10/720409 was filed with the patent office on 2005-05-26 for cmp polishing heads retaining ring groove design for microscratch reduction.
Invention is credited to Chen, Feng, Leong, Lup San, Lim, Cing Gie, Wang, Sim Kit.
Application Number | 20050113002 10/720409 |
Document ID | / |
Family ID | 34591540 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050113002 |
Kind Code |
A1 |
Chen, Feng ; et al. |
May 26, 2005 |
CMP polishing heads retaining ring groove design for microscratch
reduction
Abstract
A chemical-mechanical polish (CMP) machine and fabrication
process using the same. The CMP machine has a CMP retaining ring
comprising: an inner peripheral surface; an outer peripheral
surface; a lower surface adapted to contact and depress an upper
surface of a polishing pad during chemical mechanical polishing of
a lower surface of a substrate. The substrate is contained within
the inner peripheral surface of the retaining ring during chemical
mechanical polishing. At least a groove on the lower surface of the
retaining ring. At least a portion of the groove has a rounded
contour. In an aspect, the groove has a semicircle profile. In
another aspect, the groove has a semicircle profile and a curved
top corner profile at adjacent to the lower surface of the
retaining ring. The retaining ring with a curved portion of groove
reduces the accumulation of dried slurry in the groove and thus
reduces micro-scratches.
Inventors: |
Chen, Feng; (Singapore,
SG) ; Lim, Cing Gie; (Singapore, SG) ; Leong,
Lup San; (Singapore, SG) ; Wang, Sim Kit;
(Singapore, SG) |
Correspondence
Address: |
WILLIAM STOFFEL
PMB 455
1735 MARKET ST. - STE. A
PHILADELPHIA
PA
19103-7502
US
|
Family ID: |
34591540 |
Appl. No.: |
10/720409 |
Filed: |
November 24, 2003 |
Current U.S.
Class: |
451/42 |
Current CPC
Class: |
B24B 37/32 20130101 |
Class at
Publication: |
451/042 |
International
Class: |
B24B 001/00 |
Claims
What is claimed is:
1. A CMP retaining ring, comprising: an inner peripheral surface;
an outer peripheral surface; a lower surface adapted to contact and
depress an upper surface of a polishing pad during chemical
mechanical polishing of a lower surface of a substrate; at least a
groove on said lower surface of said retaining ring; and said
groove extending from a position at or adjacent said inner
peripheral surface of said retaining ring, to a position at or
adjacent said outer peripheral surface of said retaining ring; at
least a portion of said groove has a rounded contour or slanted
contour.
2. The CMP retaining ring of claim 1 wherein said groove has a
semicircle profile.
3. The CMP retaining ring of claim 1 wherein said groove has a
semicircle profile and said groove has a rounded top corner
adjacent to the lower surface of the retaining ring.
4. The CMP retaining ring of claim 1 wherein said groove has a
semicircle profile with a radius between 2 and 15 mm.
5. The CMP retaining ring of claim 1 wherein said groove has at
least one rounded corner.
6. The CMP retaining ring of claim 1 wherein said groove has
rounded corners adjacent to the bottom of said grooves.
7. The CMP retaining ring of claim 1 wherein said groove has
rounded top corners adjacent to the lower surface of said retaining
ring.
8. The CMP retaining ring of claim 1 wherein the cross-sectional
area of said groove changes along the length of said groove.
9. The CMP retaining ring of claim 1 wherein said groove has a
width between 1 mm and 30 mm; said groove has a depth between 1 and
15 mm.
10. The CMP retaining ring of claim 1 wherein said groove has
vertical sidewalls or sloped sidewalls.
11. The CMP retaining ring of claim 1 wherein said groove has
vertical sidewalls and an about horizontal bottom and at least one
rounded corner between said vertical sidewalls and said horizontal
bottom.
12. The CMP retaining ring of claim 1 wherein said groove has
straight sidewalls and top and bottom corners; at least one of said
corners is rounded or curvilinear.
13. The CMP retaining ring of claim 1 wherein said retaining ring
can further comprise other channels; the lower surface of the
retaining ring can further comprise a plurality of protrusions and
recesses or a mixture of both.
14. A process for chemical-mechanical polishing a substrate
comprising: said substrate is disposed within a polishing head
facing a polishing table; said substrate is retained within the
polishing head by a retainer ring, and at least a portion of said
groove has a rounded contour; supplying a slurry to said polishing
table or to said polish head; moving the polishing table and/or the
polishing head to chemically polish the wafer.
15. The process of claim 14 which further includes: said substrate
is a wafer; forming a deposition layer on the surface of said wafer
and chemical mechanically polishing said deposition layer.
16. The process of claim 14 wherein said groove has a semicircle
profile.
17. The process of claim 14 wherein said groove has a semicircle
profile and said groove has a rounded corner adjacent to the lower
surface of the retaining ring.
18. The process of claim 14 wherein said groove has at least one
rounded corner.
19. The process of claim 14 wherein said grooves has at least one
rounded bottom corner.
20. The process of claim 14 wherein said groove has rounded edges
adjacent to the bottom of said grooves.
21. The process of claim 14 wherein said groove has rounded top
edges adjacent to the lower surface of said retaining ring.
22. The process of claim 14 wherein said groove has a width between
1 and 30 mm; said groove has a depth between 1 and 15 mm.
Description
BACKGROUND OF INVENTION
[0001] 1) Field of the Invention
[0002] Embodiments of this invention relate to Chemical Mechanical
Polishing (CMP) methods and machines, and particularly to retaining
ring designs for CMP heads and more particularly to retaining ring
designs with curved grooves for reducing microscatches on
semiconductor structures.
[0003] 2) Description of the Related Art
[0004] In semiconductor fabrications, the chemical-mechanical
polish (CMP) technique is widely used for the global planarization
of semiconductor wafers that are used for the fabrication of VLSI
(very large-scale integration) and ULSI (ultra large-scale
integration) integrated circuits.
[0005] FIGS. 1A and 1B are schematic diagrams showing a
conventional CMP machine. The CMP machine comprises a polishing
table 10 on which a polishing pad 12 is layered, a polishing head
14 for holding a semiconductor wafer 16 in position, and a nozzle
18 for applying a mass of slurry to the semiconductor wafer 16
during the CMP process.
[0006] FIG. 1C shows a respective view of the structure inside of
the polishing head 14. As shown, the polishing head 14 includes an
air-pressure means 20 which applies air pressure to a wafer loader
22 used to hold the wafer 16. In addition, a retainer ring 24 is
mounted around the loader 22 and the wafer 16, which can retain the
wafer 16 in fixed position during the CMP process. Moreover, a
cushion pad (not shown) is placed between the wafer 16 and the
loader 22.
[0007] A problem of current chemical-mechanical polish (CMP)
machines and process is the micro-scratches formed on the substrate
during the CMP process.
[0008] The importance of overcoming the various deficiencies noted
above is evidenced by the extensive technological development
directed to the subject, as documented by the relevant patent and
technical literature. The closest and apparently more relevant
technical developments in the patent literature can be gleaned by
considering U.S. Pat. No. 6,386,962 (Gotkis et al.) that shows a
wafer carrier with retainer ring for a chemical-mechanical polish
(CMP) apparatus.
[0009] U.S. Pat. No. 6,527,624 B1 (Tollers et al.) shows a
retaining ring.
[0010] U.S. Pat. No. 6,110,025 (Williams et al.) teaches a retainer
ring with passages.
[0011] U.S. Pat. No. 6,293,850 B1 (Lin et al.) shows retaining ring
with slurry passages at the bottom of the retainer ring.
[0012] U.S. Pat. No. 6,224,472 B1 (Lai et al.) teaches a retaining
ring with channels.
[0013] However, the retaining rings can be further improved.
SUMMARY OF THE INVENTION
[0014] It is an object of example embodiments of the present
invention to provide a retaining ring for use in a
chemical-mechanical polish (CMP) machine.
[0015] It is an object of example embodiments of the present
invention to provide a CMP method and a retaining ring having
channels with rounded contour or rounded corners or curved surfaces
for use in a chemical-mechanical polish (CMP) machine.
[0016] An example embodiment of the present invention provides a
retaining ring which is characterized as follows. A CMP retaining
ring, comprising:
[0017] an inner peripheral surface;
[0018] an outer peripheral surface;
[0019] a lower surface adapted to contact and depress an upper
surface of a polishing pad during chemical mechanical polishing of
a lower surface of a substrate; the substrate is contained within
the inner peripheral surface of the retaining ring during chemical
mechanical polishing; and
[0020] at least a groove on the lower surface of the retaining ring
and extending from a position at or adjacent the inner peripheral
surface of the retaining ring, to a position at or adjacent the
outer peripheral surface of the retaining ring;
[0021] at least a portion of the groove has a rounded contour.
[0022] In another aspect, the groove has a semicircle profile.
[0023] In another aspect, the groove has a semicircle profile and
the groove has a rounded top corner adjacent to the lower surface
of the retaining ring.
[0024] An example embodiment of a process of the invention is
described as follows. A process for chemical-mechanical polish
(CMP) a wafer comprising:
[0025] the wafer is disposed within a polishing head with the
deposition layer facing a polishing table; the wafer is retained
within the polishing head by a retainer ring, and
[0026] at least a portion of the groove has a rounded contour;
[0027] supplying a slurry to the polish table and/or polish
head;
[0028] rotating the polishing table and spinning the polishing head
to chemically polish the wafer.
[0029] Another aspect further includes: forming a deposition layer
on the surface of the wafer and chemical mechanically polishing the
deposition layer.
[0030] Another aspect further includes: the groove has a semicircle
profile.
[0031] Another aspect further includes: the groove has a semicircle
profile and the groove has a rounded corner adjacent to the lower
surface of the retaining ring.
[0032] The above advantages and features are of representative
embodiments only, and are not exhaustive and/or exclusive. They are
presented only to assist in understanding the invention. It should
be understood that they are not representative of all the
inventions defined by the claims, to be considered limitations on
the invention as defined by the claims, or limitations on
equivalents to the claims. For instance, some of these advantages
may be mutually contradictory, in that they cannot be
simultaneously present in a single embodiment. Similarly, some
advantages are applicable to one aspect of the invention, and
inapplicable to others. Furthermore, certain aspects of the claimed
invention have not been discussed herein. However, no inference
should be drawn regarding those discussed herein relative to those
not discussed herein other than for purposes of space and reducing
repetition. Thus, this summary of features and advantages should
not be considered dispositive in determining equivalence.
Additional features and advantages of the invention will become
apparent in the following description, from the drawings, and from
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The features and advantages of a retaining ring and methods
thereof according to example embodiments the present invention will
be more clearly understood from the following description taken in
conjunction with the accompanying drawings in which like reference
numerals designate similar or corresponding elements, regions and
portions and in which:
[0034] FIG. 1A is a schematic top view of a chemical-mechanical
polish (CMP) machine for performing a CMP process on a
semiconductor wafer according to the prior art.
[0035] FIG. 1B is a schematic section view of the
chemical-mechanical polish (CMP) machine of FIG. 1A according to
the prior art.
[0036] FIG. 1C is a cross sectional view showing an inside
structure of the polishing head used on the CMP machine of FIGS. 1A
and 1B according to the prior art.
[0037] FIG. 2A is perspective view of a retaining ring having
rectangular grooves 204.
[0038] FIG. 2B is a close up perspective view a groove in a
retaining ring having rectangular grooves 204 as shown in FIG.
2A.
[0039] FIG. 2C is a cross sectional view of a groove that has
slurry particles that cause the problems as discovered by the
inventors.
[0040] FIG. 3A is perspective view of a retaining ring that has
non-rectangular grooves 304 according to an aspect of the
invention.
[0041] FIG. 3B is a close up perspective view of an embodiment
where the groove has a semicircle profile according to an aspect of
the invention.
[0042] FIG. 3C is a cross sectional view of a groove that has a
semicircle profile according to an aspect of the invention.
[0043] FIG. 3D is a cross sectional view of a groove that has
rounded or curved or non-angular bottom corners and curved
sidewalls 316 according to an aspect of the invention.
[0044] FIG. 3E is a cross sectional view of a groove that has
rounded or curved or non-angular bottom corners 311, rounded top
corners 320 and slanted or sloped sidewalls 322 according to an
aspect of the invention.
[0045] FIG. 3F is a cross sectional view of a groove 304F that has
rounded or curved or non-angular bottom corners and about vertical
sidewalls 316 and a flat bottom 316 according to an aspect of the
invention.
[0046] FIG. 4A is perspective view of a retaining ring that has
non-rectangular grooves 404 and curved top corners according to an
aspect of the invention.
[0047] FIG. 4B is a close up perspective view of an embodiment
where the groove has curved top corners according to an aspect of
the invention.
[0048] FIG. 4C is a cross sectional view of a groove that has a
semicircle profile and curved top corners according to an aspect of
the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] Introduction
[0050] Referring now to the drawings and more particularly to FIGS.
2A, 2B, and 2C, there is shown a retaining ring 200 over which the
aspects of the present invention are an improvement. It is to be
understood in this regard that no portion of FIGS. 2A, 2B and 2C is
admitted to be prior art as to the present invention. Rather, this
these diagrams are an effort to provide an improved understanding
of some of the problems that are overcome by the aspects of the
invention.
[0051] FIG. 2A is perspective view of a retaining ring 200 having
rectangular shaped grooves 204. The ring has a lower surface 201
(polishing surface or pad side surface) that in operation faces the
polish pad.
[0052] FIG. 2B is a close up perspective view a groove 204 that has
non-curved corners or edges in the a retaining ring 200.
[0053] FIG. 2C is a cross sectional view of a groove 204 that has
slurry particles or other debris 208 that cause the problems as
discovered by the inventors.
[0054] Microscratches are a defect caused by the CMP process. Big
particles and/or dry slurry are causes of the microscrathes. Big
particle size can be control by filtration in the supplier's
factory and the dried slurry is hard material normally found the
in-house slurry delivery related components. The forming of dried
slurry can occur when the water vaporizes from the slurry droplet
spilled on the surface of some polishing machine components.
[0055] The inventors have found that the retaining ring in the
chemical-mechanical polish (CMP) machine is a source of dried
slurry. As shown in FIG. 2C, the corner of the groove of the wafer
polishing head's retaining ring was found to accumulate a few
chunks of dried slurry. A purpose of these grooves is to allow the
slurry flow in to the wafer polishing head for efficient
planarization process. Unfortunately, the design of the current
retaining ring grooves can cause slurry particles to accumulate and
increase micro scratches.
Example Embodiments of the Grooves of the Invention
[0056] Example embodiments of the grooves of the invention have at
least a portion of the groove or the surface adjacent to the groove
is curved. Examples of curvilinear portions of groove are:
semicircle shaped grooves, arc shapes grooves, groves with rounded
bottom corners, grooves with rounded top corners, grooves with
curved sidewalls, grooves with slanted sidewalls, and combinations
thereof. The example embodiment of the grooves reduce the buildup
of dried slurry in grooves and thus reduce microscratches.
[0057] As shown in FIG. 3A, a chemical-mechanical polish (CMP)
retaining ring 300 comprises: an inner peripheral surface 303; an
outer peripheral surface 302; and a lower surface 301. The lower
surface 301 is adapted to contact and depress an upper surface of a
polishing pad during chemical mechanical polishing of a lower
surface of a substrate contained within the inner peripheral
surface of the retaining ring during chemical mechanical
polishing.
[0058] The retaining ring can be economically and speedily
fabricated through the injection molding, casting or other molding
processes. The mold can be built to contain the sizable cavity with
the retaining ring's net shape. The most commonly used materials
for retaining ring, normally but not limited to thermosetting or
thermoplastic polymer, is heated to highly plastic state and forced
to flow into the cavity. The solidified molded part or the
retaining ring is removed from the cavity and sent for other
finishing or shaping processes.
[0059] The retaining ring 300 has grooves 304 on the lower surface
301. The grooves 304 preferably extend from a position at or
adjacent the inner peripheral surface of the retaining ring, to a
position at or adjacent the outer peripheral surface of the
retaining ring. The cross sectional area of the groove can be
constant or changes along the length of the groove. Preferably, at
least a portion of the groove 304 has a rounded contour. Preferably
the cross sectional shape of the groove is rounded or has rounded
corners. Preferably the cross section of the groove does not
contain a portion (possibly other than the top corner) where two
flat areas meet at a angle, such as a 90 degree angle. Preferably,
the groove has a shape that reduces the amount of dried slurry and
other particles that accumulates in the groove during a polish
operation.
[0060] The term "rounded" can mean: curved, or with curved parts:
having curved, not straight or angular, surfaces or edges.
[0061] The grooves may not have the same cross sectional area along
the length of the groove. The grooves can preferably have a depth
between 2 and 15 mm. From a top down view, the groove can have any
shape, such as a straight shape as shown in FIG. 3A or can be
curved or some combination thereof.
[0062] FIG. 3B shows a closer view of a preferred embodiment of the
invention where the groove 304C has an about semicircle
profile.
[0063] FIG. 3C shows a cross sectional view of a groove 304C that
has a semicircle cross-sectional profile 310 with a radius 311. The
grooves 304C have a semicircle profile preferably with a radius 311
between 2 mm and 15 mm. The semicircle profile of the groove helps
prevent the slurry particles from accumulating in the groove.
[0064] In the aspect shown in FIG. 3D, the groove 304D has curved
sidewalls 316 and a rounded bottom corner 312 and a flat bottom
314. The grooves can have at least one rounded corner. The grooves
have rounded corners/edges 312 adjacent to the bottom 314 of the
grooves. The rounded corners, edges or surfaces 312 can prevent
slurry form accumulating in the groove.
[0065] In an aspect, the retaining ring has grooves with rounded
top edges adjacent to the lower surface 301 of the retaining
ring.
[0066] Referring to FIG. 3E, an aspect is shown where the groove
304E has a rounded top corner 320 near the lower surface of the
ring. The groove has a sloped sidewall 322. The groove has a
slanted contour. Slanted means the sidewall has a least a section
that is not at about a 90 degree angle with the lower surface 301
of the ring. The groove has a rounded bottom corner 311 and a flat
316 bottom. The bottom can be flat or curved.
[0067] In an aspect shown in FIG. 3F, the CMP retaining ring has a
groove has with about vertical sidewalls 330 and an about
horizontal flat bottom 316 and at least one rounded corner 311
between the vertical sidewalls 330 and the horizontal bottom 316.
The grooves can have a width between 1 and 30 mm.
[0068] FIG. 4A shows another embodiment where the groove 404 has
top corner or edge with a curved shape.
[0069] FIG. 4B shows a perspective view of the groove 404 with the
rounded top corner 420. In the aspect shown in FIGS. 4B and 4C the
groove has a semicircle profile 410 and top rounded corners
420.
[0070] FIG. 4C shows a preferred embodiment of the invention of a
groove 404C with rounded top corners 420 and a semicircle profile
410. In an option, the rounded top corners 420 can have the shape
of a arc of a circle having a radius 413. In an option, the
semicircle profile 410 can have radius 411.
[0071] The retaining ring can have other channels on the lower
surface. Also, the lower surface of the retaining ring can further
comprise a plurality of protrusions and recesses or a mixture of
both. In addition, the retaining ring can have other passages thru
the ring such as a passage connecting the grooves to the top side
of the ring. See e.g., U.S. Pat. No. 6,527,624 B1.
[0072] It will be understood that CMP retaining rings embodiments
of the invention may be advantageously used with any type of CMP
polishing system, pad material and/or polishing slurry, such as
where the lower (or pad-side) surface of the retaining ring
contacts the polishing pad during polishing. Examples of suitable
CMP slurries include, but are not limited to, Cabot "SS25", Cabot
"SS12".
[0073] It should be noted that the retaining ring and wafer
carriers of the present invention may be used with any suitable CMP
systems such as linear CMP apparatus or rotary CMP apparatus.
[0074] Process Using the Retaining Ring of Aspects of the
Invention
[0075] The retaining rings of the aspects of the invention can be
used in a process to CMP a substrate. The substrate is preferably a
wafer with layers formed or deposited thereover. The layers can be
insulating and/or conducting layers. The insulating layers can be
comprised of oxide, (e.g., oxide made from tetraethylorthosilicate
(TEOS)) or low-k materials. The conductive layers can be metal
layers such as copper alloys, or Aluminum alloys.
[0076] A process for chemical-mechanical polishing a wafer
comprises the following.
[0077] The wafer is disposed within a polishing head with the
deposition layer facing a polishing table. The wafer is retained
within the polishing head by a retainer ring.
[0078] The retaining ring is a ring according to an aspect of the
invention describe above. For example, at least a portion of the
groove has a rounded contour.
[0079] We supply a slurry to the polishing table or the polish
head.
[0080] We move the polishing table and/or the polishing head to
chemically polish the wafer. Preferably, we rotate the polishing
table and spin the polishing head to chemically polish the wafer.
Preferably the polish table has a polish pad thereover and the
polish pad polishes the substrate.
[0081] In the above description numerous specific details are set
forth in order to provide a more thorough understanding of the
present invention. It will be obvious, however, to one skilled in
the art that the present invention may be practiced without these
details. In other instances, well known process have not been
described in detail in order to not unnecessarily obscure the
present invention.
[0082] Given the variety of embodiments of the present invention
just described, the above description and illustrations show not be
taken as limiting the scope of the present invention defined by the
claims.
[0083] While the invention has been particularly shown and
described with reference to the preferred embodiments thereof, it
will be understood by those skilled in the art that various changes
in form and details may be made without departing from the spirit
and scope of the invention. It is intended to cover various
modifications and similar arrangements and procedures, and the
scope of the appended claims therefore should be accorded the
broadest interpretation so as to encompass all such modifications
and similar arrangements and procedures.
* * * * *