U.S. patent application number 10/887259 was filed with the patent office on 2005-01-13 for method for hardening the wear portion of a retaining ring.
Invention is credited to Leitao, Carlos Madeira, Sather, Alvin William.
Application Number | 20050005416 10/887259 |
Document ID | / |
Family ID | 33567803 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050005416 |
Kind Code |
A1 |
Sather, Alvin William ; et
al. |
January 13, 2005 |
Method for hardening the wear portion of a retaining ring
Abstract
A one piece plastic or two piece, metal and plastic, retaining
ring used for chemical mechanical polishing of semiconductor
substrates. In one embodiment, the plastic is selected from
polyphenylene sulfide (PPS), polyethylene terephthalate,
polyetheretherketone, polybutylene terephthalate, Ertalyte TX,
PEEK, Torlon, Delrin, PET, Vespel, or Duratrol. The plastic wear
surface is hardened by electron beam or gamma ray irradiation.
Inventors: |
Sather, Alvin William;
(Georgetown, TX) ; Leitao, Carlos Madeira;
(Austin, TX) |
Correspondence
Address: |
William Sather
300 Park Central Blvd
Georgetown
TX
78626
US
|
Family ID: |
33567803 |
Appl. No.: |
10/887259 |
Filed: |
July 8, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60485572 |
Jul 8, 2003 |
|
|
|
Current U.S.
Class: |
29/463 ;
29/557 |
Current CPC
Class: |
B24B 37/32 20130101;
Y10T 29/49893 20150115; Y10T 29/49995 20150115 |
Class at
Publication: |
029/463 ;
029/557 |
International
Class: |
B24B 005/00; B24B
047/02 |
Claims
What is claimed is:
1. A method of fabricating a multilayer retaining ring for a CMP
carrier head the method comprising machining a metal upper portion;
machining a lower plastic portion; attaching the lower portion to
the upper portion, such that the plastic portion has an exposed
bottom surface; and treating the exposed plastic bottom surface
with electron beam irradiation, thereby hardening the surface of
the plastic portion.
2. The method of claim 1 wherein the plastic is selected from the
group from a material selected from the group consisting of
polyphenylene sulfide (PPS), polyethylene terephthalate,
polyetheretherketone, polybutylene terephthalate, Ertalyte TX,
PEEK, Torlon, Delrin, PET, Vespel, or Duratrol;
3. A method of fabricating a multilayer retaining ring for a CMP
carrier head the method comprising machining a metal upper portion;
machining a lower plastic portion; attaching the lower portion to
the upper portion, such that the plastic portion has an exposed
bottom surface; and treating the exposed plate surface with gamma
ray irradiation, thereby hardening at least the surface of the
plastic portion.
4. The method of claim 1 wherein the plastic portion is selected
from the group consisting of polyphenylene sulfide (PPS),
polyethylene terephthalate, polyetheretherketone, polybutylene
terephthalate, Ertalyte TX, PEEK, Torlon, Delrin, PET, Vespel, or
Duratrol.
5. A method of fabricating a plastic retaining ring, the method
comprising machining the plastic ring, the ring having a lower wear
surface; and hardening at least the wear surface of the ring with a
radiation process.
6. The method of claim 5 wherein the radiation process is an
electron beam process.
7. The method of claim 5 wherein the radiation process is a gamma
ray process.
Description
RELATED APPLICATIONS
[0001] This application is related to and claims priority from U.S.
Provisional patent application No. 60/485,572 filed Jul. 8,
2003.
FIELD OF INVENTION
[0002] This invention relates to an electron beam radiation and
gamma ray radiation process for hardening the wear portion of a one
part or two part retaining ring typically used in chemical
mechanical polishing operations.
BACKGROUND
[0003] The present invention relates to a retaining ring used in
the process of chemical mechanical polishing of semiconductor
substrates. The substrate is typically a thin disc of semiconductor
material with deposited alternate layers of conductive,
semiconductive, and insulating materials. The layers are etched to
produce electrical circuitry on the surface of the substrate. A
typical substrate has a series of layers deposited and circuitry
etched. The deposition and etching process after many layers
produces a non flat top surface. This lack of flatness prevents
accurate deposition of subsequent layers. Planarization of the
substrate is periodically required to maintain an acceptable
substrate surface.
[0004] Chemical mechanical polishing of the topmost surface of the
substrate produces a sufficiently flat surface to allow accurate
subsequent deposition and etching of layers. This method of
planarization is affected on a substrate by use of a polishing
machine. Among the many subassemblies of this machine is the
polishing head or carrier head. The polishing head contains among
its components a retaining ring. This ring positions and retains
the substrate allowing the other components of the head to exert
pressure against the substrate which in turn moves relative to a
polishing pad, usually wetted by a polishing medium or slurry.
[0005] In one embodiment, the retaining ring is formed from two
pieces. The first, or upper, piece is usually of a metal material
such as stainless steel, aluminum, or molybdenum, but may be other
materials. The second, or lower, piece is of a plastic material
such as polyphenylene sulfide (PPS), polyethylene terephthalate,
polyetheretherketone, polybutylene terephthalate, Ertalyte TX,
PEEK, Torlon, Delrin, PET, Vespel, or Duratrol.
[0006] In other embodiments, a single part plastic retaining ring
may be provided.
[0007] There is a need for CMP retaining rings with harder surfaces
which resist wear, thereby extending the life of the retaining
ring.
SUMMARY
[0008] The invention is directed toward a method of treating the
plastic wear portion of a retaining ring used in the chemical
mechanical polishing process of a semiconductor substrate. The
plastic portion of a one or two part retaining ring includes a wear
surface which contacts a polishing pad. In one embodiment of the
current invention, the lower wear surface of the plastic portion of
the retaining ring is subjected to electron beam radiation in order
to harden the surface. In another embodiment the wear surface is
subjected to gamma ray radiation to harden the material.
[0009] The prior art establishes some improvement is material
properties from electron beam radiation or gamma ray radiation of
polymers. It is believed that such radiation has a detrimental
effect because of the scission of polymer chains, but that this
detrimental effect is partially offset at relatively low doses of
radiation by the realignment of the rings which improves the
surface hardness. It is desirable in semiconductor processing such
as chemical mechanical polishing operations to provide a
multi-layer ring that has a polymer wear portion which has improved
wear characteristics. The wear characteristic is related to the
hardness of the plastic, and radiation of a ring can improve the
hardness and thereby improve wear characteristics of the retaining
ring.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other objects and advantages of the present
invention are set forth below and further made clear by reference
to the drawings, wherein:
[0011] FIG. 1 is a cross sectional view of the retaining ring.
[0012] FIG. 2 is a flow chart of a manufacturing process for a two
part ring.
[0013] FIG. 3 is a flow chart of a manufacturing process for a one
part ring.
DETAILED DESCRIPTION OF EMBODIMENT
[0014] Retaining Ring
[0015] Referring now to FIG. 1 which is a cross sectional view of a
two part retaining ring, the retaining ring 10 is composed of an
upper part 15 is typically made of a metal, and the lower part 25
is typically made of plastic. In one embodiment, the upper and
lower parts are attached with an adhesive 50 such as an acrylic
adhesive or a urethane adhesive. The lower part of the ring
includes a wear surface 40.
[0016] Referring now to FIG. 2, in this embodiment the two part
ring is fabricated by machining the metal upper portion at step
100, machining the lower plastic portion at step 110, joining the
metal and plastic portion at step 120, processing the assembled
ring at step 130, and hardening the plastic at step 140. The
attachment at step 120 may be by adhesive attachment at step 122,
or by mechanical attachment at step 125. Adhesive attachment
typically includes grit blasting the mating surfaces of the metal
and plastic parts with #24 ceramic abrasive to a finish of 150-250
RMS; degreasing the upper and lower portions, solvent cleaning the
mating surfaces with acetone, applying an adhesive to the mating
surface of the plastic portion of the ring, placing the metal
portion on top of the plastic portion pressing the pieces together
with a force of about 50 pounds until excess adhesive is squeezed
out in a continuous bead around the ring and the adhesive has a
thickness in the range of 0.007" to 0.012"; removing the excess
adhesive, and permitting the ring to cure at room temperature for a
minimum of 24 hours. Adhesives, such as urethanes, acrylics, or
epoxies may be used. In alternate embodiments, the two parts may be
mechanically attached such as screwed together at step 124, or self
threaded at step 128, or press fit at step 126.
[0017] In one embodiment, the first material is stainless steel and
the second material is polyphenylene sulfide which includes
TechTron.sup.R by Quadrant, Ryton.sup.R by Chevron-Phillips, and
Ensinger by Ensinger Corporation.
[0018] Other plastics such as polyphenylene sulfide (PPS),
polyethylene terephthalate, polyetheretherketone, polybutylene
terephthalate, Ertalyte TX, PEEK, Torlon, Delrin, PET, Vespel, or
Duratrol.
DETAILED DESCRIPTION OF EMBODIMENT
[0019] Electron Beam Radiation of Polyphenylene Sulfide Multilayer
Ring
[0020] In this embodiment a multi-layer polyphenylene sulfide and
metal ring is provided. After fabrication of the two part
multi-layer ring at step 142, the PPS surface is subjected to
electron beam radiation to harden the first few millimeters of
depth. The electron beam irradiation is preferably between 0.5 and
2 MV. At a temperature of about 150.quadrature.C. A temperature
range of room temperature to slightly below the melting point of
the plastic may be used.
[0021] In an alternative embodiment, the plastic portion of the
ring may be treated by electron beam radiation before being
assembled to the metal portion.
DETAILED DESCRIPTION OF EMBODIMENT
[0022] Electron Beam Radiation of Polyphenylene Sulfide Single Part
Ring
[0023] Referring now to FIG. 3, in this embodiment a single part
polyphenylene sulfide plastic retaining ring is fabricated at step
150. After fabrication, the PPS bottom wear surface is subjected to
electron beam radiation at step 162 to harden the first few
millimeters of depth.
DETAILED DESCRIPTION OF EMBODIMENT
[0024] Electron Beam Radiation of Other Plastic Rings
[0025] In this embodiment, a retaining ring is fabricated as a
single part plastic ring or as a multilayer ring of metal and a
plastic. The plastic may include polyphenylene sulfide (PPS),
polyethylene terephthalate, polyetheretherketone, polybutylene
terephthalate, Ertalyte TX, PEEK, Torlon, Delrin, PET, Vespel, or
Duratrol.
DETAILED DESCRIPTION OF EMBODIMENT
[0026] Gamma Ray Radiation of Polyphenylene Sulfide
[0027] In this embodiment a multi-layer ring of polyphenylene
sulfide and metal and is subjected to gamma ray radiation at step
144 after fabrication.
[0028] In an alternative embodiment, the plastic portion of the
ring may be treated by gamma ray radiation before being assembled
to the metal portion. The gamma ray radiation is preferably at a
dose rate of 1 kGy/s by .sup.60Cobalt in a vacuum at a temperature
of about 150.quadrature.C. A temperature range of room temperature
to slightly below the melting point of the plastic may be used.
DETAILED DESCRIPTION OF EMBODIMENT
[0029] In this embodiment the polyphenylene sulfide is a single
part ring subject to gamma ray radiation at step 164 after
fabrication of the ring.
* * * * *