U.S. patent application number 11/542303 was filed with the patent office on 2008-02-28 for ethylene terephthalate polymer retaining ring for a chemical mechanical polishing head.
Invention is credited to Peter Lao, Gerard Stephen Moloney.
Application Number | 20080051011 11/542303 |
Document ID | / |
Family ID | 39107569 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080051011 |
Kind Code |
A1 |
Moloney; Gerard Stephen ; et
al. |
February 28, 2008 |
Ethylene terephthalate polymer retaining ring for a chemical
mechanical polishing head
Abstract
Embodiments of a retaining ring for use with a chemical
mechanical polishing process with a body including a polyethylene
terephthalate polymer or polymer including ethylene terephthalate
monomers are disclosed.
Inventors: |
Moloney; Gerard Stephen;
(Sacramento, CA) ; Lao; Peter; (Elk Grove,
CA) |
Correspondence
Address: |
SQUIRE, SANDERS & DEMPSEY L.L.P.
1 MARITIME PLAZA, SUITE 300
SAN FRANCISCO
CA
94111
US
|
Family ID: |
39107569 |
Appl. No.: |
11/542303 |
Filed: |
October 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60839552 |
Aug 22, 2006 |
|
|
|
Current U.S.
Class: |
451/41 ;
451/285 |
Current CPC
Class: |
B24B 37/32 20130101 |
Class at
Publication: |
451/41 ;
451/285 |
International
Class: |
B24B 7/30 20060101
B24B007/30; B24B 29/00 20060101 B24B029/00 |
Claims
1. A retaining ring for use in a chemical mechanical polishing
process, a body of the retaining ring comprises a PET polymer,
wherein the PET polymer is free or substantially free of inorganic
particles.
2. The retaining ring of claim 1, wherein the inorganic particles
comprise filler particles, nucleating agents, or both.
3. The retaining ring of claim 1, wherein a portion of the body of
the retaining ring comprises the PET polymer.
4. The retaining ring of claim 1, wherein all or a majority of the
body of the retaining ring comprises the PET polymer.
5. The retaining ring of claim 1, wherein the body of the retaining
ring comprises at least one additional polymer blended with the PET
polymer.
6. The retaining ring of claim 1, wherein the body of the retaining
ring further comprises organic filler particles dispersed within
the PET polymer in an amount less than or equal to 2% by
weight.
7. The retaining ring of claim 6, wherein the organic particles
comprise TEFLON particles.
8. A retaining ring for use in a chemical mechanical polishing
process, a body of the retaining ring comprises a polymer, the
polymer comprising ethylene terephthalate monomers, wherein the
polymer is free or substantially free of inorganic particles.
9. The retaining ring of claim 8, wherein the inorganic particles
comprise filler particles, nucleating agents, or both.
10. The retaining ring of claim 8, wherein all or a majority of the
body of the retaining ring comprises the polymer including the
ethylene terephthalate monomer.
11. The retaining ring of claim 8, wherein a portion of the body of
the retaining ring comprises the polymer including the ethylene
terephthalate monomers.
12. The retaining ring of claim 8, wherein the polymer is a
copolymer, the copolymer comprising one or more additional
monomers.
13. The retaining ring of claim 12, wherein the additional monomers
are selected from the group consisting of phenylene sulfide and
etherketone.
14. The retaining ring of claim 8, wherein a majority of the
polymer comprises ethylene terephthalate monomers.
15. The retaining ring of claim 8, wherein the body of the
retaining ring comprises at least one additional polymer blended
with the polymer.
16. The retaining ring of claim 8, wherein the body of the
retaining ring further comprises organic filler particles dispersed
within the polymer in an amount less than or equal to 2.0 % by
weight.
17. The retaining ring of claim 16, wherein the organic particles
comprise TEFLON particles.
18. A method of polishing a substrate comprising: providing a
chemical mechanical polishing apparatus comprising a retaining ring
having a body, the body including a polymer including a PET
polymer, wherein the polymer is free or substantially free of
inorganic particles; retaining the substrate using the retaining
ring; and polishing the substrate including the step of placing the
body in contact with a polishing pad surface.
19. The method of claim 18, wherein the body of the retaining ring
is free of organic particles.
20. The method of claim 18, wherein all or a majority of the body
of the retaining ring comprises the PET polymer.
21. The method of claim 18, wherein the body of the retaining ring
further comprises organic filler particles dispersed within the PET
polymer.
22. A method of polishing a substrate comprising the step of:
providing a chemical mechanical polishing apparatus, the apparatus
comprising a retaining ring having a body, the body comprising
ethylene terephthalate monomer, wherein the polymer is free or
substantially free of inorganic particles; retaining the substrate
using the retaining ring; and polishing the substrate including the
step of placing the body in contact with a polishing pad
surface.
23. The method of claim 22, wherein the body of the retaining ring
is free of organic particles.
24. The method of claim 22, wherein a majority of the polymer
comprises ethylene terephthalate monomers.
25. The method of claim 22, wherein the polymer is a copolymer, the
copolymer comprising one or more additional monomers.
26. The method of claim 22, wherein the body of the retaining ring
further comprises organic filler particles dispersed within the
polymer.
27. A retaining ring for use in a chemical mechanical polishing
process, a body of the retaining ring comprises a PET polymer,
wherein the PET polymer has organic filler particles dispersed
therein and the PET polymer is free or substantially free of
inorganic particles.
28. The retainer ring of claim 27, wherein the PET polymer has less
than 0.1% organic particles dispersed therein.
29. A retaining ring for use in a chemical mechanical polishing
process, a body of the retaining ring comprises a polymer, the
polymer comprising ethylene terephthalate monomers, wherein the
polymer has organic filler particles dispersed therein and the
polymer is free or substantially free of inorganic particles.
30. The retainer ring of claim 29, wherein the polymer has less
than 0.1% organic particles dispersed therein.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of U.S. provisional
application No. 60/839,552, filed on Aug. 22, 2006, the teachings
of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to chemical mechanical
polishing (CMP), and more particularly, to a retaining ring for use
in a CMP apparatus.
[0004] 2. Description of the State of the Art
[0005] The present invention relates to a polishing apparatus for
polishing a plate-like article such as a semiconductor wafer or an
optical lens. In particular, the invention relates to a retaining
ring, an integral part of the polishing apparatus. In manufacturing
integrated circuits, optical devices and the like, it is important
that a workpiece used to form an integrated circuit, optical
device, or the like have a highly planar surface.
[0006] A polishing technique referred to as Chemical Mechanical
Polishing (CMP) has been commonly employed to polish semiconductor
wafers. CMP is a combination of chemical reaction and mechanical
buffing. In CMP, a semiconductor wafer held by a rotating carrier
body is brought into contact with a polishing surface provided on a
rotating turntable while an alkali or acid abrasive slurry is
supplied onto the polishing surface, whereby the wafer is polished
both mechanically under relative motion between the rotating
carrier body and the rotating turntable, and chemically by the
supplied slurry. In this way, the wafer surface can be polished to
an exceptionally high degree of flatness.
[0007] A critical component of a CMP system is a retaining ring. A
conventional CMP system includes a polishing head with a retaining
ring that holds and rotates the wafer against a pad surface
rotating in the opposite direction or same direction. Thus, the
function of the retaining ring is to contain and position the wafer
as it is being planarized. Also, by adjusting the force on the
retaining ring, the removal rate on the edge of the wafer can be
adjusted. This is due to a change in the pad rebound
characteristics as the force applied to the retaining ring is
changed.
[0008] With proper material selection and design these rings can
offer low wear rates, uniform surface finish with a tight flatness
tolerance and absence of large-scale topography in addition to high
material stability with low vibration characteristics. An important
problem with retaining rings is that they can cause defects on the
polished wafer during the polishing process. As the retaining ring
and the wafer contact the pad during the polishing process, a
particle that is present in the retaining ring material may become
dislodged as the retaining ring wears. The dislodged particle can
travel on the pad surface under the wafer causing a defect on the
wafer. These defects can result in defective die on the wafer, thus
decreasing the yield from each wafer.
SUMMARY OF THE INVENTION
[0009] Certain embodiments of the present invention include a
retaining ring for use in a chemical mechanical polishing process,
a body of the retaining ring comprises a PET polymer, wherein the
polymer is free or substantially free of inorganic particles.
[0010] Further embodiments of the present invention include a
retaining ring for use in a chemical mechanical polishing process,
a body of the retaining ring comprises a polymer, the polymer
comprising ethylene terephthalate monomers, wherein the polymer is
free or substantially free of inorganic particles.
[0011] Other embodiments of the present invention include a method
of polishing a substrate comprising: polishing a substrate with a
chemical mechanical polishing apparatus, the apparatus comprising a
retaining ring that holds and rotates the substrate against a
polishing pad surface, a body of the retaining ring comprising a
polymer including a PET polymer, wherein the polymer is free or
substantially free of inorganic particles.
[0012] Additional embodiments of the present invention include a
method of polishing a substrate comprising: polishing a substrate
with a chemical mechanical polishing apparatus, the apparatus
comprising a retaining ring that holds and rotates the substrate
against a polishing pad surface, a body of the retaining ring
comprises a polymer, the polymer comprising ethylene terephthalate
monomers, wherein the polymer is free or substantially free of
inorganic particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 depicts a block diagram illustrating a cross section
of a prior art retaining ring.
[0014] FIGS. 2-3 depict the substrate removal rate as function of
position across polished wafers in tests using talc-containing and
talc-free retaining rings.
[0015] FIGS. 4-7 depict bar charts of defect results on wafers
polished using talc-containing and talc-free retaining rings.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIG. 1 is a block diagram illustrating a cross section of a
prior art retaining ring, substrate, and pad. A retaining ring 30
is cylindrical in shape and holds a substrate 40 in place during
CMP. Retaining ring 30 has an outer portion 10 and a center portion
20. Retaining ring 30 includes a lower surface 32 for contacting a
polishing pad 110 during CMP, an inner surface 34 for retaining a
substrate, an outer surface 36, a top surface 38, and a topper
surface 50 that essentially caps the hollow region of retaining
ring 30. Retaining ring 30, in addition to functioning to hold
substrate 40 in place, functions to press the pad 110 in a lateral
motion during the polishing process. The retaining ring depicted in
FIG. 1 is provided as an example only. There are many variations in
retaining ring design. The present invention is not limited to the
retaining ring design depicted in FIG. 1.
[0017] Retaining rings can be made from various kinds of polymers,
both filled and unfilled with filler particles. Filler particles or
fillers refer to particles dispersed within a polymer.
Representative polymers can include, but are not limited to,
polyphenylene sulfide (PPS), polyetherketone (PEEK), or polyesters.
Fillers can be added to a polymer for a variety of reasons,
including, but not limited to, facilitating processing of a polymer
or enhancing the mechanical properties of the polymer. A polymer
for use in a retaining ring can also include particles that are
nucleating agents that are used in the synthesis of the polymer.
Representative inorganic fillers include, but are not limited to,
talc, alumina, and titanium oxide. It is believed that polymers
with inorganic fillers used in retaining rings can increase or
cause defects on the polished wafers during polishing.
[0018] Various embodiments of the present invention include a
retaining ring in which a body of the retaining ring includes or
contains a polyethylene terephthalate (PET) polymer that is free or
substantially free of inorganic particles. Such inorganic particles
may refer to inorganic fillers or inorganic nucleating agents. For
example, the PET polymer can be free or substantially free of
talc.
[0019] Further embodiments of the present invention include a
retaining ring in which a body of the retaining ring includes or
contains a polymer including ethylene terephthalate (ET) monomer
that is free or substantially free of inorganic particles. In an
embodiment, the polymer is a copolymer including one or more
additional types of monomers or functional groups. For example,
additional monomers or functional groups can include, but are not
limited to phenylene sulfide and/or etherketone. The copolymer can
be a random copolymer or have alternating monomers or functional
groups.
[0020] In some embodiments, a majority of the copolymer includes ET
monomers. In exemplary embodiments, the copolymer can have greater
than about 50 wt %, 65 wt %, 80 wt %, 95 wt %, or greater than
about 99 wt % ET monomer. In additional embodiments, the present
invention can include a retaining ring in which a body of the
retaining ring includes or contains a blend of a PET polymer and an
ET-containing copolymer. As used herein, "PET/ET" refers to a PET
polymer, an ET-containing polymer, and/or a blend of a PET polymer
and an ET-containing polymer.
[0021] In one embodiment "substantially free" can refer to a weight
fraction of inorganic particles in the body or the
PET/ET-containing portion of the body of the retaining ring at
which substrate defects caused by the inorganic particles during
polishing are essentially eliminated or not detectable by
standardized measurement techniques. A representative example of a
commercially available PET-containing polymer is Ertalyte.RTM.
PET-P manufactured by Quadrant Engineering Plastic Products of
Bridgeport, Conn.
[0022] In one embodiment, all or a majority of the body of the
retaining ring includes or contains the PET polymer or ET monomers
of an ET-containing polymer. Alternatively, a portion of the body
of the retaining ring includes or contains the PET or ET-containing
polymer. In one embodiment, a portion of the retaining ring that is
subjected to wear can include or contain the PET/ET polymer. For
example, portion 10 of retaining ring 30 in FIG. 1 can be made from
the PET/ET polymer.
[0023] In certain embodiments, a majority of the body or the
PET/ET-containing portion of the body of the retaining ring can be
composed of the PET polymer or ET monomers of the ET-containing
copolymer. In some exemplary embodiments, the body or the
PET/ET-containing portion of the body of the retaining ring can be
greater than about 50 wt %, 65 wt %, 80 wt %, 95 wt %, or greater
than about 99 wt % PET or ET monomers of the ET-containing
copolymer. In one embodiment, the body or the PET-containing
portion of the body of the retaining ring is 100 wt % PET
polymer.
[0024] In further embodiments, the body or the PET/ET-containing
portion of the body of the retaining ring can be a blend of the
PET/ET polymer and at least one additional polymer. In one
embodiment, the PET/ET polymer and the additional polymer(s) can be
a uniform or substantially uniform polymer blend. In an embodiment,
the PET/ET polymer and the additional polymer(s) are a miscible
blend. Alternatively, the PET/ET polymer and at least one
additional polymer are immiscible, so that the PET/ET polymer and
the additional polymer form an immiscible blend. The PET/ET polymer
and the additional polymer(s) can be mixed or dispersed uniformly
or substantially uniformly.
[0025] In additional embodiments, the body or the PET/ET-containing
portion of the body of the retaining ring can include organic
filler particles dispersed within the PET/ET polymer. In some
embodiments, the organic particles can decrease the coefficient of
friction between the retaining ring and contacting surfaces. It is
believed that organic filler particles will not increase the
likelihood of defects in a substrate during polishing as is the
case with inorganic particles. A representative organic filler is
TEFLON. The weight percent of organic filler in the polymer can be
less than 0.1%, between 0.1-1%, between 1-2%, or greater than
2%.
[0026] In some embodiments, a retaining ring can be fabricated by
methods including injection molding or extrusion. In additional
embodiments, a polymer can be formed into a stock shape and
machined or milled to form a retaining ring using methods that are
known in the art.
[0027] It has been demonstrated that the use of a PET-based
material, Ertalyte.RTM. PET-P, without inorganic fillers or
inorganic nucleating agents, in a retaining ring results in
significantly less defects on the polished wafer while having a
similar removal rate and uniformity profiles to commercially
available talc-containing Ertalyte.RTM.. In addition, the lifetime
of a retaining ring made from talc-containing Ertalyte.RTM. and
retaining rings made from the talc-free material have been shown to
be similar. Typically, the lifetime for a retaining ring made from
PET material is four times that of PPS and two times that of PEEK,
making PET an excellent option as a retaining ring material.
EXAMPLES
[0028] The examples and experimental data set forth below are for
illustrative purposes only and are in no way meant to limit the
invention. The following examples are given to aid in understanding
the invention, but it is to be understood that the invention is not
limited to the particular materials or procedures of the
examples.
[0029] A comparison was performed of the break-in time and defects
of retaining rings made from Quadrant Ertalyte with talc filler and
retaining rings made with talc-free Quadrant Ertalyte.
[0030] The experimental setup included a polishing tool, polishing
pad, slurry, and wafers. The polishing tool was an F*Rex300 w/300
mm MPTI Multi-Zone Head (Ertalyte SC & DSI) and a 3M A9
Dresser. The polishing pad was an IC1000-P/Suba400 and the slurry
was SC-112. The wafers used were thermal Ox (15K.ANG.) and TEOS
(8K.ANG.). The process conditions were
BSP/CZP/SCP/RRP=200/160/120/170 hPa; TT/TR=45/46 rpm. The thickness
metrology was a Nanometrics 8300. The defect metrology was a KLA
Tencor SP-1.
[0031] Removal Rate and Uniformity Comparison
[0032] In Table 1 the removal rate (RR) in Angstrom/min and
uniformity of wafers using retaining rings made from
talc-containing Ertalyte.RTM. and talc-free Ertalyte.RTM. are
compared. As shown, tests were performed for two different wafers.
The removal rate and the percent nonuniformity (NU %) are similar
for the talc-containing and talc-free retaining rings. 81 pt DS
refers to 81 measurement points across the diameter of the wafer
and 121 CS refers to 121 measurement points in a polar pattern
across the wafer. NU % is a measure of the removal rate variation
within the 81 pt DS or 121 pt CS wafers.
[0033] FIG. 2 depicts the removal rate as a function of position
across the 81 pt DS wafer using the talc-containing Ertalyte.RTM.
and talc-free Ertalyte.RTM. retaining rings. FIG. 3 depicts the
removal rate as a function of position or measurement site number
across the 121 pt CS wafer using the talc-containing Ertalyte.RTM.
and talc-free Ertalyte.RTM. retaining rings. The removal rate is
very similar for both retaining rings.
TABLE-US-00001 TABLE 1 Comparison of Removal Rate and Uniformity of
retaining rings made from talc-containing Quadrant Ertalyte .RTM.
and talc-free Quadrant Ertalyte .RTM.. 81 pt DS 121 pt CS RR
(A/min) NU % RR (A/min) NU % Quadrant (Talc) 931 4.59 914 3.65
Quadrant (No Talc) 951 5.25 929 2.71
[0034] Run Sequence for Defect and Lifetime Tests
[0035] There was a pad break-in of 600 sec for both the
talc-containing Ertalyte.RTM. and talc-free Ertalyte.RTM. retaining
rings.
[0036] The run sequence for the talc-containing Ertalyte.RTM.
retaining ring is as follows: 1 Teos Wafer+1 Dummy Ox+1 Teos
Wafer+2 Dummy Ox+1 Teos Wafer+3 Dummy Ox+1 Teos Wafer+4 Dummy Ox+1
Teos Wafer+5 Dummy Ox+1 Teos Wafer.
[0037] The run sequence for the talc-free Ertalyte.RTM. retaining
rings is as follows: 1 Teos Wafer+1 Dummy Ox+1 Teos Wafer+2 Dummy
Ox+1 Teos Wafer+3 Dummy Ox+1 Teos Wafer+4 Dummy Ox+1 Teos Wafer+5
Dummy Ox+1 Teos Wafer.
[0038] A repeat test of 3 Teos wafers was performed for each
retaining ring.
[0039] Defect Count in Wafers Using Talc-Containing Ertalyte.RTM.
and Talc-Free Ertalyte.RTM. Retaining Rings
[0040] Table 2 is a summary of the defect count in wafers for the
talc-containing Ertalyte.RTM. and talc-free Ertalyte.RTM. retaining
rings. FIGS. 4 and 5 depict a bar chart of defect results for the
talc-containing Ertalyte.RTM. and talc-free Ertalyte.RTM. retaining
rings, respectively. FIG. 6 depicts a bar chart including defect
results in wafers for both the talc-containing Ertalyte.RTM. and
talc-free Ertalyte.RTM. retaining rings. "Pre" refers to the
defects on the wafer prior to polishing, "Post" refers to the
defects on the wafer after polishing, and "Adder" refers to the
"Post" defects minus the "Pre" defects.
[0041] As shown by the results for the talc-containing
Ertalyte.RTM. retaining rings, the initial defect count was high,
but stabilized at about 200 adders after 4.about.5 wafers. The
wafer defect count with the talc-free Ertalyte.RTM. retaining rings
was low initially, and stabilized at about 100 adders after about
3.about.4 wafers. Wafers polished with the talc-free Ertalyte.RTM.
retaining ring had lower defect adders and a quicker break-in time
than the talc-containing Ertalyte.RTM. retaining ring.
TABLE-US-00002 TABLE 2 Wafer Defect Summary for retaining rings
made from Quadrant talc- containing Ertalyte .RTM. and talc-free
Quadrant Ertalyte .RTM.. Standard Ertalyte - Quadrant Ertalyte -
Quadrant(Talc) (No Talc) Wafer # Pre Post Adder Pre Post Adder 1
175 1769 1594 51 401 350 3 20 249 229 35 132 97 6 20 198 178 31 146
115 10 33 239 206 69 185 116 15 45 220 175 65 156 91 21 22 223 201
35 143 108 average 53 483 198 48 194 105 (excludes initial)
[0042] The test summarized in Table 1 was repeated with the
talc-containing Ertalyte.RTM. and talc-free Ertalyte.RTM. retaining
rings with 3 Teos Wafers with a different slurry than SC-112. The
repeat test was performed with a different lot of the brand of
slurry SC-112. The results are summarized in Table 3 and FIG. 7.
The talc-free Ertalyte.RTM. exhibits lower wafer defect adders with
the different lot of slurry.
TABLE-US-00003 TABLE 3 Wafer Defect Summary of repeat test with
different lot of slurry for retaining rings made with
talc-containing Quadrant Ertalyte .RTM. and talc-free Quadrant
Ertalyte .RTM.. Standard Ertalyte - Quadrant Ertalyte - Quadrant
(Talc) (No Talc) Wafer # Pre Post Adder Pre Post Adder 22 113 347
234 115 231 116 23 76 235 159 58 135 77 24 59 256 197 43 118 75
average 83 279 197 72 161 89
[0043] To summarize, there is no significant difference in terms of
oxide film removal rate and nonuniformity between the
talc-containing Ertalyte.RTM. and talc-free Ertalyte.RTM. retaining
rings. For the talc-containing Ertalyte.RTM. retaining ring, the
wafer defect number stabilizes after 4.about.5 wafers with the
defect adder of 200. For the talc-free Ertalyte.RTM. retaining
ring, the wafer defect number stabilizes after just 3.about.4
wafers with the defect adder of 100. The talc-free Ertalyte.RTM.
retaining ring achieves better defect numbers with a faster
break-in time on the polished wafers. The repeat test confirms the
talc-free Ertalyte.RTM. retaining ring has the lower wafer defect
numbers.
[0044] While particular embodiments of the present invention have
been shown and described, it will be obvious to those skilled in
the art that changes and modifications can be made without
departing from this invention in its broader aspects. Therefore,
the appended claims are to encompass within their scope all such
changes and modifications as fall within the true spirit and scope
of this invention.
* * * * *