U.S. patent application number 09/918683 was filed with the patent office on 2003-03-13 for electrochemically roughened aluminum semiconductor processing apparatus surfaces.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Stow, Clifford C., Sun, Jennifer Y., Thach, Senh.
Application Number | 20030047464 09/918683 |
Document ID | / |
Family ID | 25440775 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030047464 |
Kind Code |
A1 |
Sun, Jennifer Y. ; et
al. |
March 13, 2003 |
Electrochemically roughened aluminum semiconductor processing
apparatus surfaces
Abstract
A uniform, controllable method for electrochemically roughening
an aluminum-comprising surface to be used in a semiconductor
processing apparatus is disclosed Typically the aluminum-comprising
surface is aluminum or an aluminum alloy. The method involves
immersing an aluminum-comprising surface in an HCl solution having
a concentration ranging from about 1 volume % to about 5 volume %,
at a temperature within the range of about 45.degree. C. to about
80.degree. C., then applying an electrical charge having a charge
density ranging from about 80 amps/ft..sup.2 to about 250
amps/ft..sup.2 for a time period ranging from about 4 minutes to
about 25 minutes. A chelating agent may be added to enhance the
roughening process. The electrochemical roughening method can be
used on aluminum alloys in general, including but not limited to
6061 and LP. The electrochemical roughening provides a smoothly
rolling surface which does not entrap particles and which provides
increased surface area for semiconductor process byproduct
adhesion. The roughened surface provides an excellent surface for
subsequent anodization.
Inventors: |
Sun, Jennifer Y.;
(Sunnyvale, CA) ; Stow, Clifford C.; (Santa Clara,
CA) ; Thach, Senh; (Union City, CA) |
Correspondence
Address: |
APPLIED MATERIALS , INC.
2881 SCOTT BLVD.
M/S 2061
SANTA CLARA
CA
95050
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
25440775 |
Appl. No.: |
09/918683 |
Filed: |
July 27, 2001 |
Current U.S.
Class: |
205/646 ;
204/224M; 205/674 |
Current CPC
Class: |
C23C 16/4404 20130101;
C25F 3/04 20130101; Y10T 428/265 20150115 |
Class at
Publication: |
205/646 ;
205/674; 204/224.00M |
International
Class: |
C25F 003/00; C25F
007/00 |
Claims
We claim:
1. A semiconductor processing chamber having at least one interior
surface comprising electrochemically roughened aluminum or aluminum
alloy.
2. The semiconductor processing chamber of claim 1, wherein said at
least one interior surface has a surface roughness ranging from
about 100 Ra to about 200 Ra.
3. The semiconductor processing chamber of claim 2, wherein said
surface roughness ranges from about 110 Ra to about 160 Ra.
4. The semiconductor processing chamber of claim 1, wherein said
electrochemically roughened aluminum or aluminum alloy surface has
the appearance of rolling hills and valleys, when magnified.
5. The semiconductor processing chamber of claim 4, wherein the
height of said hills ranges from about 8 .mu.m to about 25
.mu.m.
6. The semiconductor processing chamber of claim 4 or claim 5,
wherein the distance between the center of one hill and the center
of an adjacent hill ranges from about 30 .mu.m to about 100
.mu.m.
7. The semiconductor processing chamber of claim 1, wherein said
electrochemically roughened aluminum or aluminum alloy surface
underlies a coating selected from the group consisting of an
anodized coating, a flame spray-deposited aluminum oxide coating, a
ceramic coating, and an anodized coating having a ceramic coating
applied thereover.
8. The semiconductor processing chamber of claim 1, wherein
byproducts generated during an etch process or a deposition process
adhere to said electrochemically roughened aluminum surface.
9. The semiconductor processing chamber of claim 1, wherein said
semiconductor processing chamber is selected from the group
consisting of an etch chamber and a deposition chamber.
10. The semiconductor processing chamber of claim 9, wherein said
semiconductor processing chamber is an etch chamber which is used
for etching a material selected from the group consisting of a
dielectric material, a metal, and polysilicon.
11. The semiconductor processing chamber of claim 9, wherein said
semiconductor processing chamber is an etch chamber, and wherein
fluorine and carbon from an etch process react to form a polymer
which adheres to said electrochemically roughened aluminum
surface.
12. A processing component for use within a semiconductor
processing chamber, wherein said processing component has at least
one electrochemically roughen ed aluminum or aluminum alloy
surface.
13. The processing component of claim 12, wherein said
electrochemically roughened aluminum or aluminum alloy surface has
a surface roughness ranging from about 100 Ra to about 200 Ra.
14. The processing component of claim 13, wherein said surface
roughness ranges from about 110 Ra to about 160 Ra.
15. The processing component of claim 12, wherein said
electrochemically roughened aluminum or aluminum alloy surface has
the appearance of rolling hills and valleys, when magnified.
16. The processing component of claim 15, wherein the height of
said hills ranges from about 8 .mu.m to about 25 .mu.m.
17. The processing component of claim 15 or claim 16, wherein the
distance between the center of one hill and the center of an
adjacent hill ranges from about 30 .mu.m to about 100 .mu.m.
18. The processing component of claim 12, wherein said
electrochemically roughened aluminum or aluminum alloy surface
underlies a coating selected from the group consisting of an
anodized coating, a flame spray-deposited aluminum oxide coating, a
ceramic coating, and an anodized coating having a ceramic coating
applied thereover.
19. The processing component of claim 12, wherein byproducts
generated during an etch process or a deposition process adhere to
said electrochemically roughened aluminum or aluminum alloy
surface.
20. The processing component of claim 12, wherein said processing
component is used within a semiconductor processing chamber
selected from the group consisting of an etch chamber and a
deposition chamber.
21. The processing component of claim 20, wherein said
semiconductor processing chamber is an etch chamber which is used
for etching a material selected from the group consisting of a
dielectric material, a metal, and polysilicon.
22. The processing component of claim 20, wherein said
semiconductor processing chamber is an etch chamber, and wherein
fluorine and carbon from an etch process react to form a polymer
which adheres to said electrochemically roughened surface.
23. The processing component of claim 12, wherein said processing
component is selected from the group consisting of: a wall liner, a
cathode liner, a slit valve door, a slit valve liner, a buffer
insert, and a gas distribution plate.
24. A semiconductor processing apparatus surface, wherein said
surface comprises electrochemically roughened aluminum or aluminum
alloy.
25. The semiconductor processing apparatus surface of claim 24,
wherein said surface has a surface roughness ranging from about 100
Ra to about 200 Ra.
26. The semiconductor processing apparatus surface of claim 25,
wherein said surface roughness ranges from about 110 Ra to about
160 Ra.
27. The semiconductor processing apparatus surface of claim 24,
wherein said electrochemically roughened aluminum or aluminum alloy
surface has the appearance of rolling hills and valleys, when
magnified.
28. The semiconductor processing apparatus surface of claim 27,
wherein the height of said hills ranges from about 8 .mu.m to about
25 .mu.m.
29. The semiconductor processing apparatus surface of claim 27 or
claim 28, wherein the distance between the center of one hill and
the center of an adjacent hill ranges from about 30 .mu.m to about
100 .mu.m.
30. The semiconductor processing apparatus surface of claim 24,
wherein said surface underlies a coating selected from the group
consisting of an anodized coating, a flame spray-deposited aluminum
oxide coating, a ceramic coating, and an anodized coating having a
ceramic coating applied thereover.
31. The semiconductor processing apparatus surface of claim 24,
wherein byproducts generated during an etch process or a deposition
process adhere to said electrochemically roughened surface.
32. The semiconductor processing apparatus surface of claim 31,
wherein fluorine and carbon from an etch process react to form a
polymer which adheres to said surface.
33. The semiconductor processing apparatus surface of claim 24,
wherein said surface is present on an apparatus component selected
from the group consisting of: a wall liner, a cathode liner, a slit
valve door, a slit valve liner, a buffer insert, and a gas
distribution plate.
34. A method for electrochemically roughening a surface comprising
aluminum or an aluminum alloy, including the steps of: a) immersing
said surface in an HCl solution having a concentration ranging from
about 1 volume % to about 5 volume %, at a temperature ranging from
about 45 .degree. C. to about 80.degree. C.; and b) applying an
electrical charge having a charge density ranging from about 80
amps/ft..sup.2 to about 250 amps/ft..sup.2 for a time period
ranging from about 4 minutes to about 25 minutes.
35. The method of claim 34, wherein said HCl solution has a
concentration ranging from about 1 volume % to about 3 volume
%.
36. The method of claim 35, wherein said temperature of said HCl
solution ranges from about 50.degree. C. to about 70.degree. C.
37. The method of claim 34, wherein said HCl solution further
includes a chelating agent, and wherein said chelating agent is
present at a concentration within the range of about 0.5 volume %
to about 3 volume %.
38. The method of claim 37, wherein said chelating agent is
gluconic acid.
39. The method of claim 34, wherein said charge density ranges from
about 120 amps/ft..sup.2 to about 250 amps/ft..sup.2.
40. The method of claim 34, wherein said time period ranges from
about 4 minutes to about 20 minutes.
41. The method of claim 34, wherein said aluminum-comprising
surface is an aluminum alloy selected from the group consisting of
6061 and LP.
42. The method of claim 41, wherein said HCl solution concentration
ranges from about 1 volume % to about 1.5 volume %; wherein said
temperature of said HCl solution ranges from about 55.degree. C. to
about 65.degree. C.; and wherein said charge density ranges from
about 175 amps/ft..sup.2 to about 250 amps/ft..sup.2.
43. The method of claim 42, wherein said HCl solution further
includes a gluconic acid chelating agent, which is present at a
concentration within the range of about 0.9 volume % to about 1.1
volume %.
44. The method of claim 43, wherein said time period during which
said charge density is present ranges from about 6 minutes to about
12 minutes, and the aluminum alloy is 6061.
45. The method of claim 43, wherein said wherein said time period
during which said charge density is present ranges from about 4
minutes to about 8 minutes, and the aluminum alloy is LP.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention pertains to an electrochemically
roughened aluminum or aluminum alloy surface for use within a
semiconductor processing chamber. The present invention also
pertains to a method of electrochemically roughening an aluminum or
aluminum alloy surface. The roughened surface is typically anodized
to provide a finished surface for use in semiconductor
processing.
[0003] 2. Brief Description of the Background Art
[0004] Semiconductor manufacturing processes, such as etch and
deposition processes, utilize a wide variety of processing gases
and substrate materials. Highly volatile process byproducts are
typically removed from the processing chamber by application of
vacuum. Less volatile byproducts may adhere to the interior surface
of the processing chamber or may redeposit on the surface of the
semiconductor substrate being processed. Most semiconductor
manufacturers prefer to have redepositing byproducts deposit on
processing chamber surfaces (rather than the substrate). The
processing chamber surfaces are then periodically cleaned. Frequent
chamber cleanings are expensive in terms of processing chamber
downtime. The more redeposited byproducts which can be held by the
processing chamber surfaces, the less frequent the cleaning
requirement.
[0005] Interior surfaces of semiconductor processing chambers are
frequently aluminum. One prior art semiconductor processing chamber
includes anodized aluminum surfaces which have been lapped to have
a surface roughness of only 4 Ra, which is essentially a mirror
finish. However, when subjected to the high temperatures and
processing conditions used in many semiconductor manufacturing
processes, the highly polished, anodized aluminum surface developed
numerous tiny cracks in the anodized layer, known as craze lines;
these are shown in FIG. 1. While the craze lines 100 typically do
not penetrate all of the way through the anodized layer to the
boundary layer at the base aluminum beneath, they tend to spread
across the anodized surface, producing a spider web pattern. During
a fluorine-based etch process, the anodized aluminum surface reacts
with fluorine gas, causing the craze lines to fill with a
self-passivating fluoride. Although the craze lines may not
interfere with the operation of the chamber during a fluorine-based
etch process, they are cosmetically unappealing, and the user of
the processing chamber tends to worry that fluorine-containing
species may be passing through the protective anodized layer and
corroding the aluminum surface beneath. Further, in a
non-fluorine-based environment (such as during a chlorine-based
etch process), the craze lines do not fill with self-passivating
fluoride and the anodized surface may eventually fail, exposing the
aluminum beneath to corrosion by chlorine-containing species.
[0006] During a number of semiconductor processing procedures,
byproducts are formed which are not sufficiently volatile to be
removed by the vacuum system of the processing chamber. In many
instances, it is desirable to provide a surface inside the
processing chamber on which these byproducts are capable of
adhering, so that they will not fall upon semiconductor workpieces
during processing, causing contamination.
[0007] One method of improving the adhesion of semiconductor
processing byproducts to an aluminum surface within a semiconductor
processing chamber is to provide a roughened surface to which
byproducts generated during processing can stick. Typically,
aluminum semiconductor chamber surfaces have been roughened by bead
blasting. However, bead blasting often is a manual process, in
which it is difficult to control the uniformity and repeatability.
Further, bead blasting typically provides a very sharp, jagged
surface 200 on the aluminum, as shown in FIG. 2. Tips of the
roughened aluminum can curl over, forming hook-shaped projections
202 which can break off or entrap particles 204, including the bead
blast particle itself. As a result, the bead blasting media may act
as a source of contamination of the aluminum surface. Bead blasting
is not useful as a roughening method for some of the softer
aluminum alloys, such as the 1000 series, because the bead blasting
particles can easily become embedded in the ductile metal. Further,
the sharp surface provided by bead blasting may complicate a
subsequent anodization process.
[0008] It would therefore be desirable to provide a uniform and
controllable method for roughening an aluminum surface which could
be used for all aluminum alloys. In particular, the roughening
method should provide a surface which does not entrap particles, is
free from jagged and hooked surface formations, and is easily
anodized.
SUMMARY OF THE INVENTION
[0009] Applicants have discovered a uniform, controllable method
for electrochemically roughening an aluminum-comprising surface
intended for use within a semiconductor processing chamber.
Typically the aluminum-comprising surface is aluminum or an
aluminum alloy. Applicants have also determined that if they
electrochemically roughen an aluminum or aluminum alloy surface,
they avoid the formation of jagged and hooked surface topography.
The surface which is formed by the electrochemical roughening
provides a topography which resembles small rolling hills and
valleys. The estimated average height of the hills above the
valleys is approximately 16 .mu.m; the estimated average distance
between the hills is approximately 50 .mu.m, depending on the grade
of the aluminum. Typically, the height of the hills ranges from
about 8 .mu.m to about 25 .mu.m, and the distance between the
center of one hill and that of an adjacent hill ranges from about
30 .mu.m to about 100 .mu.m.
[0010] Surprisingly, the hill and valley topography obtained by
electrochemically roughening an aluminum or aluminum alloy surface
relieves stress in an anodized finish subsequently produced over
the roughened surface, so that the anodized layer does not crack
upon thermal cycling up to about 300.degree. C. In addition,
unexpectedly, the amount of redepositing byproduct which can be
accumulated over the hills and valleys (including an anodized
surface which mirrors the underlying aluminum surface) is
drastically increased over that which can be accumulated over a
bead-blasted surface. As a result, the number of substrate
processing cycles prior to cleaning with the new, electrochemically
roughened, aluminum or aluminum alloy anodized surface is about 5
times greater than with the bead blasted aluminum anodized
surface.
[0011] Applicants' method for surface roughening can be used on
aluminum and aluminum alloys in general, including but not limited
to 6061 and LP (available from Alcan Alusuisse). Applicants' method
promotes formation of a smooth, rolling-hilled, anodized surface
which does not entrap particles. Further, applicants'
electrochemically roughened aluminum-comprising surfaces provide
increased surface area for collection of redepositing
byproducts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows a prior art anodized aluminum surface 100 which
has been lapped to have a surface roughness of 4 Ra. Note the many
craze lines 102 which have formed in the aluminum surface
subsequent to exposure to process conditions, producing a spider
web pattern.
[0013] FIG. 2 shows a prior art aluminum surface 200 which has been
roughened using bead blasting. Note the many hook-shaped
projections 202 which can break off or entrap particles 204,
including the bead blast particle itself.
[0014] FIG. 3 shows an aluminum surface 300 which has been
roughened using applicants' electrochemical roughening method. Note
the smooth, rolling topography of applicants' electrochemically
roughened aluminum surface.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Applicants' invention pertains to a method of
electrochemically roughening an aluminum-comprising surface.
Typically the aluminum-comprising surface is aluminum or an
aluminum alloy. Aluminum is commonly alloyed with elements such as
silicon, copper, zinc, magnesium, manganese, iron, titanium, and
nickel, by way of example, and not by way of limitation.
Applicants' invention has use in semiconductor processing chambers
which include electrochemically roughened aluminum surfaces, and
particularly roughened surfaces having a protective coating
thereover, such as an anodized aluminum coating.
[0016] Applicants' method for electrochemically roughening an
aluminum-comprising surface comprises immersing the
aluminum-comprising surface in an aqueous HCl solution having a
concentration ranging from about 1 volume % to about 5 volume % at
a temperature ranging from about 45.degree. C. to about 80.degree.
C., then applying an electrical charge having a charge density
ranging from about 80 amps/ft..sup.2 to about 250 amps/ft..sup.2
for a time period ranging from about 5 minutes to about 25 minutes.
Chelating agents (such as, for example, but without limitation,
gluconic acid, available from VWR Scientific Products, West
Chester, Pa.) may be added to the HCl solution to control the bath
chemistry and conductivity.
[0017] Typical processing conditions for electrochemically
roughening aluminum and aluminum alloys according to applicants'
method are presented in Table One, below.
1TABLE ONE Typical Process Conditions for Electrochemically
Roughening Aluminum and Aluminum Alloys Typical Preferred Optimum
Process Process Known Process Process Parameter Conditions
Conditions Conditions HCl Concentration (% volume) 1-5 1-3 1-1.5
Chelating Agent (% volume) 0.5-3 0.5-1.5 0.8-1.2 Tank Temperature
(.degree. C.) 45-80 50-70 55-65 AC Frequency (Hz) 60-120 80-100
85-95 Charge Density (amps/ft..sup.2) 80-250 120-250 150-250 Time
(min.) 4-25 4-20 4-20
[0018] Processing conditions will need to be adjusted depending on
the specific chemical composition of the particular aluminum alloy
being roughened. Applicants have performed electrochemical
roughening of several commercially available aluminum alloys.
Specific processing conditions used during the electrochemical
roughening of these alloys are presented in Table Two, below.
2TABLE TWO Process Conditions for Electrochemically Roughening
Particular Aluminum Alloys Alloy Process Condition 6061* LP** HCl
Concentration (% volume) 1.0-1.5 1.0-1.5 Gluconic Acid*** (%
volume) 0.9-1.1 0.9-1.1 (Chelating Agent) Tank Temperature
(.degree. C.) 55-65 55-65 AC Frequency (Hz) 85-95 85-95 Charge
Density (amps/ft..sup.2) 175-250 175-250 Time (min.) 6-12 4-8 *Can
be obtained from any of the major aluminum manufacturers, such as
Alcoa (Pittsburgh, PA), Alcan, Inc. (Montreal, Canada), and
Reynolds Aluminum Supply Co. (Richmond, VA). **Obtained from Alcan
Alusuisse (Stegen, Germany). ***Obtained from VWR Scientific
Products (West Chester, PA).
[0019] Unroughened, machined aluminum and aluminum alloy typically
has a surface roughness ranging from about 12 Ra to about 32 Ra.
After performing applicants' electrochemical roughening method, the
aluminum or aluminum alloy surface typically has a surface
roughness ranging from about 100 Ra to about 200 Ra, preferably
ranging from about 110 Ra to about 160 Ra.
[0020] As shown in FIG. 3, applicants' aluminum and aluminum alloy
roughening method provides a surface 300 having a topography
resembling small rolling hills and valleys. The estimated average
height of the hills above the valleys is approximately 16 .mu.m;
the estimated average distance between the hills is approximately
50 .mu.m, depending on the grade of the aluminum. Typically, the
height of the hills ranges from about 8 .mu.m to about 25 .mu.m,
and the distance between the center of one hill and that of an
adjacent hill ranges from about 30 .mu.m to about 100 .mu.m.
Applicants' electrochemically roughened aluminum or aluminum alloy
surface provides increased surface area for collection of
redepositing byproducts, but does not entrap particles.
[0021] Applicants' electrochemical roughening method is
particularly useful for roughening aluminum and aluminum alloy
surfaces which are subsequently protected by a plasma-resistant
coating, for use within semiconductor processing chambers, such as
an etch chamber or a deposition chamber. Applicants' method is
particularly useful for roughening any apparatus surface which
comes into contact with semiconductor processing byproducts.
Applicants' electrochemically roughened aluminum or aluminum alloy
surface provides pockets in the hills and valleys which provide for
the accumulation of semiconductor processing byproducts, such as
etch byproducts or CVD deposition byproducts, preventing the
byproducts from redepositing on the surface of the semiconductor
substrate being processed. It is helpful to use a protective
coating applied over the aluminum or aluminum alloy surface which
provides for adhesion of depositing byproducts. Example protective
coatings include anodic oxide, flame spray-deposited aluminum
oxide, and other ceramic coatings which may be conductive or
non-conductive.
[0022] In particular, during a fluorine-based etch process,
fluorine and carbon from the etch process react to form a polymer
which easily adheres to an electrochemically roughened, anodized
aluminum surface.
[0023] Applicants' electrochemically roughened, anodized aluminum
or anodized aluminum alloy surfaces can be included in etch
chambers which are used for etching dielectric materials (including
inorganic dielectric materials, such as silicon oxide, silicon
nitride, silicon oxynitride, and tantalum pentoxide, and organic
dielectric materials, such as an organic low-k dielectric
material), metals (such as aluminum, copper, titanium, tantalum,
and tungsten), and polysilicon, by way of example, and not by way
of limitation.
[0024] Applicants' method can be used to create roughened surfaces
for semiconductor processing chamber components such as wall
liners, cathode liners, slit valve doors, slit valve liners, buffer
inserts, and gas distribution plates, by way of example, and not by
way of limitation.
[0025] Anodization of applicants' electrochemically roughened
aluminum and aluminum alloy surfaces can be performed using
conventional aluminum anodization techniques known in the art, such
as by following Mil Standard No. A-8625F, by way of example, and
not by way of limitation. Because applicants' roughening method
relieves stress within the aluminum or aluminum alloy surface, the
resulting anodized surface does not form craze lines, even when
subjected to the temperature cycling which occurs due to particular
semiconductor manufacturing processes.
[0026] Other protective, plasma-resistant coatings, such as flame
spray-deposited aluminum oxide and other ceramic coatings, can be
deposited or applied over a roughened aluminum or aluminum alloy
surface using techniques known in the art. Ceramic coatings, either
conductive or non-conductive, may be applied over a roughened,
anodized surface.
[0027] The above described preferred embodiments are not intended
to limit the scope of the present invention, as one skilled in the
art can, in view of the present disclosure expand such embodiments
to correspond with the subject matter of the invention claimed
below.
* * * * *