U.S. patent application number 11/411757 was filed with the patent office on 2007-06-21 for method of manufacturing aluminum and aluminum alloy sputtering targets.
Invention is credited to Shih-Ying Chen, Po-Chun Hsu, Ren-An Luo, Chia-Hsiang Peng, Shan Torng, Fan-Chun Tseng, Chune-Ching Young.
Application Number | 20070137831 11/411757 |
Document ID | / |
Family ID | 38172083 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070137831 |
Kind Code |
A1 |
Torng; Shan ; et
al. |
June 21, 2007 |
Method of manufacturing aluminum and aluminum alloy sputtering
targets
Abstract
A manufacturing method of sputtering targets uses a direct-chill
method to fabricate various aluminum and aluminum alloy ingots.
Without the need of follow-up forging processes, the fabricated
aluminum alloy ingots can be cut to attain aluminum and aluminum
alloy sputtering targets. The method according to the present
invention features the advantages of few process steps, high
productivity, and high yield. In addition, the fabricated targets
have small grains, fine precipitate phases, and homogeneous
composition.
Inventors: |
Torng; Shan; (Longtan
Township, TW) ; Young; Chune-Ching; (Longtan
Township, TW) ; Chen; Shih-Ying; (Taoyuan City,
TW) ; Hsu; Po-Chun; (Sanchong City, TW) ;
Peng; Chia-Hsiang; (Taichung, TW) ; Tseng;
Fan-Chun; (Pingjhen City, TW) ; Luo; Ren-An;
(Longtan Township, TW) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Family ID: |
38172083 |
Appl. No.: |
11/411757 |
Filed: |
April 27, 2006 |
Current U.S.
Class: |
164/487 ;
164/444 |
Current CPC
Class: |
B22D 21/007 20130101;
C23C 14/3414 20130101; B22D 11/003 20130101 |
Class at
Publication: |
164/487 ;
164/444 |
International
Class: |
B22D 11/124 20060101
B22D011/124 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2005 |
TW |
094145170 |
Claims
1. A method of manufacturing aluminum and aluminum alloy sputtering
targets, wherein a direct-chill method is used to fabricate pure
metal aluminum, or aluminum alloy sputtering targets alloyed with
at least one of elements chosen from the group consisting of
copper, manganese, silicon, magnesium, zinc, titanium, scandium,
zirconium, vanadium, chromium, iron, cobalt, lithium, silver,
yttrium, hafnium, tantalum, and carbon; and without follow-up
forging processes, the targets fabricated being small in grains,
being fine in precipitate phases, and being homogeneous in
structures.
2. The method of manufacturing aluminum and aluminum alloy
sputtering targets of claim 1, wherein the targets include pure
metal aluminum, or aluminum alloy alloyed with at least one of
elements chosen from the group consisting of copper, manganese,
silicon, magnesium, zinc, titanium, scandium, zirconium, vanadium,
chromium, iron, cobalt, lithium, silver, yttrium, hafnium,
tantalum, and carbon.
3. The method of manufacturing aluminum and aluminum alloy
sputtering targets of claim 2, wherein the targets include pure
metal aluminum, or aluminum alloy alloyed with other different
elements, the content of said other different elements being
smaller than or equal to 15%.
4. The method of manufacturing aluminum and aluminum alloy
sputtering targets of claim 2, wherein grain sizes of the
fabricated targets are below 100 micrometers.
5. The method of manufacturing aluminum and aluminum allots
stuttering targets of claim 2, wherein sizes of secondary
precipitate phases of the fabricated targets are below 50
micrometers.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a manufacturing technology
of aluminum and aluminum alloy targets used for thin-film
sputtering in semiconductor and optoelectronic industries. By using
a direct-chill casting method, aluminum and aluminum alloy targets
suitable for semiconductor and optoelectronic industries can be
manufactured.
BACKGROUND OF THE INVENTION
[0002] Aluminum thin films have the characteristics of high
reflectivity and low resistivity, thereby they are usually applied
in manufacturing reflection layers of CD-ROMs, interconnection
layers of semiconductors, and electrode layers of display devices.
In general, apparatus for manufacturing aluminum alloy thin films
is mainly by sputter processes. A sputter process uses plasma to
bombard targets, so that the surface atoms of the target are
scattered to escape the surface thereof and are deposited on a
substrate. After processes of adhesion, adsorption, surface
migration, and nucleation, a thin film is formed on the substrate.
The quality of the thin film depends on sputter machines and
sputtering parameters. In addition, it also depends significantly
on the quality of the target used. The characteristics of targets
include purity, grain size, density, and sizes of precipitates,
which characteristics influence seriously on uniformity of
sputtered thin films.
[0003] Generally, fabrication of metal targets mainly uses a
casting method or a powder metallurgy method. The casting method
melts and mixes component elements. Afterwards, the melt is
dispensed into molds and quenched to form an ingot. Because there
exists the problems of shrinkage voids, air voids, large grain
sizes, and composition segregation in structures made by normal
casting, the fabricated ingot has to be refined to improve its
structure. For example, according to Taiwan patent number 117,131,
after a target billet is cast, it is deformed by rolling or
forging, and the coarse cast structure can be improved by
recrystallization in terms of a hot treatment, and larger
proeutectic phases can be refined and be distributed uniformly. In
addition, according to U.S. Pat. No. 6,723,187, the ingot
fabricated by casting is processed by hot forging and four to six
passes of equal channel angular extrusion (ECAE). Besides,
intermediate annealing is carried out between passes of ECAE such
that recovery and recrystallization phenomena occur on the original
cast structure, and grains can be refined gradually and precipitate
phases can be refined and be distributed uniformly as well.
Although this method can fabricate grains with sizes below 20
micrometers, the disadvantages thereof are complex and
time-consuming of follow-up processes, and expensive process
costs.
[0004] Furthermore, according to Taiwan patent number 541,350, by
using vacuum induction melting (VIM) together with the double-V
melting process of vacuum arc remelting (VAR), the problems of
segregation, coarse inner grains, and deeper shrinkage voids caused
by insufficient cooling inside of the ingot in the single-V (VIM)
melting process can be improved. The process can be used for
fabricating homogeneous and high-purity metal alloy targets such as
aluminum, titanium, or copper alloy targets. Nevertheless, because
the method needs to be operated in a high-vacuum environment,
equipment investments for fabricating aluminum alloy targets is
relatively costly. Besides, the method needs two passes of melting,
which consequently lengthens production time.
[0005] Accordingly, the traditional casting processes of
fabricating aluminum and aluminum alloy targets are relatively
complicated. Up to now, there is no manufacturing method with a
simple process and high productivity.
SUMMARY
[0006] The purpose of the present invention is to provide a method
for manufacturing high-quality aluminum alloy targets suitable for
semiconductor and optoelectronic industries. The features of the
present invention include that follow-up sintering, hot pressing,
or forging and rolling processes are not needed, and that vacuum
environments are not necessary for melting to cast aluminum alloy
targets with fine grains, fine precipitate phases, and homogeneous
structures. The process according to the present invention also
features high yield and high productivity.
[0007] The manufacturing method of aluminum and aluminum alloy
targets according to the present invention is a direct-chill
casting method. The principle thereof is dispensing processed melt
steadily into casting molds cooled by water. When the melt passes
and contacts the surfaces of the molds, heat is brought away
rapidly via heat conduction and the melt solidifies to form a
surface solid-state thin shell. Then, said surface solid-state thin
shell is flushed by a cooling spout to quench the inside thereof
continuously, and thereby form a solid-state ingot. The ingot
follows the casting platform and is moved with a constant speed
until the predetermined casting length is achieved (vertical
direct-chill casting). If a horizontal scheme is adopted,
continuous production is possible. The casting process does not
need to be operated in a vacuum environment as, required by the
double-V process. In addition, it is not necessary to carry out
follow-up molding processes on the cast targets like traditional
casting methods. Thereby, the manufacturing method according to the
present invention is capable of fabricating aluminum alloy targets
with a thin surface composition segregation layer as well as with a
fine cast grain structure.
[0008] The present invention adopts a direct-chill casting method
with appropriate pre-melt processes to fabricate pure metal
aluminum, or aluminum alloy sputtering targets alloyed with at
least one of elements chosen from the group consisting of copper,
manganese, silicon, magnesium, zinc, titanium, scandium, zirconium,
vanadium, chromium, iron, cobalt, lithium, silver, yttrium,
hafnium, tantalum, and carbon. The grain sizes of fabricated
targets are below 100 micrometers; the sizes of secondary
precipitate phases are below 50 micrometers. Consequently, the
method according to the present invention is suitable for
mass-producing high-quality aluminum alloy targets for
semiconductor and optoelectronic industries.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a lateral cross-sectional metallurgical
microscopic photograph of an aluminum-silicon-magnesium alloy
target fabricated by a direct-chill casting method according to the
present invention;
[0010] FIG. 2 is another lateral cross-sectional metallurgical
microscopic photograph of an aluminum-silicon-magnesium alloy
target fabricated by a direct-chill casting method according to the
present invention;
[0011] FIG. 3 is a lateral cross-sectional metallurgical
microscopic photograph of an aluminum-titanium alloy target
fabricated by a direct-chill casting method according to the
present invention; and
[0012] FIG. 4 is another lateral cross-sectional metallurgical
microscopic photograph of an aluminum-titanium alloy target
fabricated by a direct-chill casting method according to the
present invention.
DETAILED DESCRIPTION
[0013] According to the present invention, embodiments of
fabricating an aluminum-titanium alloy target and an
aluminum-silicon-magnesium alloy target using a vertical
direct-chill casting method are described as follows.
Embodiment 1
[0014] A pure aluminum ingot with high purity is added into a
graphite crucible with 500 kg capacity. After the aluminum ingot is
melt completely by heating the crucible using heating wires, a pure
magnesium ingot and an aluminum-silicon master alloy are added, and
the temperature of the aluminum melt is raised above the liquidus
temperature. After the raw materials are melting, the aluminum melt
is dreg-removed, degassed, and held. Then, the aluminum melt is
injected into a flooding tank system. When the melt flows past the
flooding tank, it is degassed in situ and is filtered by a porous
ceramic filtering board to reduce contents of hydrogen and
miscellaneous non-metal articles in the aluminum melt. Besides,
casting is carried out above the liquidus temperature, wherein the
casting uses a 4-inch direct-chill mold with four mold cavities.
After casting is completed, four aluminum-silicon-magnesium alloy
sticks with a 3-meter length and a 4-inch diameter are attained.
Afterwards, both ends of the sticks are cut by 10 centimeters
(approximately 4 inches) and sputtering targets are thereby
fabricated. The yield of production is above 90%.
[0015] FIG. 1 and FIG. 2 are lateral cross-sectional metallurgical
microscopic photographs of a fabricated target. As shown in the
figure, after casting, the structure of the target is mainly
cellular cast structure. The grain sizes thereof are below 100
micrometers, and there exists no other precipitate phases
inside.
Embodiment 2
[0016] A pure aluminum ingot with high purity is added into a
graphite crucible with 500 kg capacity. After the aluminum ingot is
melt completely by heating the crucible using heating wires, a pure
titanium flake is added, and the temperature of the aluminum melt
is raised above the liquidus temperature of the Al--Ti phase
diagram to make the added titanium flake melt completely.
Meanwhile, inert gas is introduced to prevent severe oxidation of
the aluminum melt under high temperatures. After the raw materials
are melting, the aluminum melt is dreg-removed, degassed, and held.
Then, the aluminum melt is injected into a flooding tank system.
When the melt flows past the flooding tank, it is degassed in situ
and is filtered by a porous ceramic filtering board to reduce
contents of hydrogen and miscellaneous non-metal articles in the
aluminum melt. Besides, casting is carried out above the liquidus
temperature of the Al--Ti phase diagram, wherein the casting uses a
4-inch direct-chill mold with four mold cavities. After casting is
completed, four aluminum-titanium alloy sticks with a 3-meter
length and a 4-inch diameter are attained. Afterwards, both ends of
the sticks are cut by 10 centimeters (approximately 4 inches) and
sputtering targets are thereby fabricated. The yield of production
is above 90%.
[0017] FIG. 3 and FIG. 4 are lateral cross-sectional metallurgical
microscopic photographs of a fabricated target. As shown in the
figure, after casting, the structure of the target is mainly
uniaxial cellular cast structure. The grain sizes thereof are below
100 micrometers, and there exists a small amount of Al.sub.3Ti
precipitate phases inside with sizes mostly below 50
micrometers.
[0018] According to the embodiments described above, it shows that,
without follow-up forging processes, the targets fabricated by the
direct-chill casting method according to the present invention are
fine in grains and in precipitate phases. The grain sizes thereof
are below 100 micrometers, and the sizes of precipitate phases
thereof are below 50 micrometers.
[0019] Accordingly, the present invention conforms to the legal
requirements owing to its novelty, unobviousness, and utility.
However, the foregoing description is only a preferred embodiment
of the present invention, not used to limit the scope and range of
the present invention. Those equivalent changes or modifications
made according to the shape, structure, feature, or spirit
described in the claims of the present invention are included in
the appended claims of the present invention.
* * * * *