U.S. patent application number 11/841165 was filed with the patent office on 2007-12-27 for process for production of ge-cr alloy sputtering target.
This patent application is currently assigned to NIPPON MINING & METALS CO., LTD.. Invention is credited to Hirohisa Ajima, Hideo Takami.
Application Number | 20070297932 11/841165 |
Document ID | / |
Family ID | 32820551 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070297932 |
Kind Code |
A1 |
Takami; Hideo ; et
al. |
December 27, 2007 |
Process for Production of Ge-Cr Alloy Sputtering Target
Abstract
A Ge--Cr alloy sputtering target containing 5 to 50 at % of Cr
and having a relative density of 95% or more, and a manufacturing
method of such a Ge--Cr alloy sputtering target wherein Cr powder
having a minus sieve of 75 .mu.m or less, and Ge powder having a
minus sieve of 250 .mu.m or less and having a BET specific surface
area of 0.4 m.sup.2/g or less are dispersively mixed in an even
manner, and sintered thereafter. Thereby provided is a Ge--Cr alloy
sputtering target capable of suppressing variation of the
deposition speed and film composition, as well as improving the
production yield, of the GeCrN layer deposited with reactive
sputtering as the intermediate layer between the recording layer
and protective layer of a phase change optical disk, and the
manufacturing method of such a target.
Inventors: |
Takami; Hideo; (Ibaraki,
JP) ; Ajima; Hirohisa; (Ibaraki, JP) |
Correspondence
Address: |
HOWSON AND HOWSON
SUITE 210
501 OFFICE CENTER DRIVE
FT WASHINGTON
PA
19034
US
|
Assignee: |
NIPPON MINING & METALS CO.,
LTD.
Tokyo
JP
|
Family ID: |
32820551 |
Appl. No.: |
11/841165 |
Filed: |
August 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10543103 |
Jul 22, 2005 |
|
|
|
PCT/JP03/12660 |
Oct 2, 2003 |
|
|
|
11841165 |
Aug 20, 2007 |
|
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Current U.S.
Class: |
419/46 ;
G9B/5.304 |
Current CPC
Class: |
C22C 28/00 20130101;
C22C 30/00 20130101; G11B 5/851 20130101; C22C 1/04 20130101; C23C
14/3414 20130101 |
Class at
Publication: |
419/046 |
International
Class: |
C22C 1/04 20060101
C22C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2003 |
JP |
2003-017025 |
Claims
1. A method of manufacturing a Ge--Cr alloy sputtering target,
comprising the steps of: evenly dispersing and mixing Cr powder of
75 .mu.m or less and Ge powder of 250 .mu.m or less, said Ge powder
having a BET specific surface area of 0.1 to 0.4 m.sup.2/g; and
thereafter performing sintering thereto.
2. A method according to claim 1, wherein said sintering is
performed under conditions of hot pressing at a sintering
temperature of 760 to 900.degree. C. and surface pressure of 75 to
250 kg/cm.sup.2.
3. A method according to claim 1, wherein said sputtering target
formed by the method contains 5 to 50 at % of Cr, has a relative
density of 97% or more and a density variation within .+-.1.5%, and
has in X-ray diffraction a ratio B/A of a maximumn peak intensity A
of Ge phase in a 2.theta. range of 20.degree. to 30.degree. and of
a maximum peak intensity B of GeCr compound phase in a 2.theta.
range of 30.degree. to 40.degree. of 0.18 or more.
4. A method according to claim 3, wherein a composition variation
in the target is within .+-.0.5%.
5. A method according to claim 3, wherein said sintering is
performed under conditions of hot pressing at a sintering
temperature of 760 to 900.degree. C. and surface pressure of 75 to
250 kg/cm.sup.2.
6. A method according to claim 5, wherein a composition variation
in the target is within .+-.0.5%.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S.
application Ser. No. 10/543,103, which is the National Stage of
International Application No. PCT/JP03/12660, filed Oct. 2, 2003,
which claims the benefit under 35 USC 119 of Japanese Application
No. 2003-017025, filed Jan. 27, 2003.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a Ge--Cr alloy sputtering
target capable of suppressing the deposition speed variation and
the accompanying composition deviation, and obtaining stable
sputtering characteristics upon forming a GeCrN thin film with
reactive sputtering employing the Ge--Cr alloy sputtering target,
and the manufacturing method thereof.
[0003] In recent years, high density recordable optical disc
technology capable of recording/reproduction without requiring a
magnetic head has been developed, and is rapidly attracting
attention. This optical disc can be classified into the three
categories of read-only, write-once, and rewritable. Particularly,
the phase change method employed in the write-once or rewritable
type discs is attracting attention.
[0004] This phase change optical disc performs the
recording/reproduction of information by heating and increasing the
temperature of a recording thin film on a substrate by irradiating
a laser beam thereto, and generating a crystallographic phase
change (amorphous.revreaction.crystal) in the structure of such
recording thin film. More specifically, the reproduction of
information is performed by detecting the change in the
reflectivity caused by the change in the optical constant of the
phase.
[0005] The aforementioned phase change is performed with the
irradiation of a laser beam narrowed down to a diameter of
approximately 1 to several .mu.m. Here, for example, when a 1 .mu.m
laser beam passes through at a linear velocity of 10 m/s, light is
irradiated to a certain point on the optical disc for 100 ns, and
it is necessary to perform the aforementioned phase change and
detect the reflectivity within such time interval.
[0006] Moreover, in order to realize the foregoing crystallographic
phase change, that is, the phase change between amorphous phase and
crystal, not only will the phase change recording layer be subject
to fusion and quenching more than once, the peripheral dielectric
protective layer and aluminum alloy will also be repeatedly subject
thereto.
[0007] In light of the above, a phase change optical disc has a
four-layer structure wherein both sides of the recording thin film
layer of a Ge--Sb--Te are sandwiched with protective layers of a
zinc sulfide-silicon oxide (ZnS--SiO.sub.2) high-melting point
dielectric, and an aluminum alloy reflective layer is additionally
provided thereto.
[0008] In the above-mentioned structure, demanded of an optical
function capable of increasing the absorption in the amorphous
portion and crystal portion and giving a large reflectivity
difference, also of a function for giving the recording film the
resistivity to moisture and preventing the deformation caused by
the heat of the recording thin film as well as a function for
controlling the thermal conditions upon recording (c.f. "Kogaku"
magazine, volume 26, no. 1, pages 9 to 15).
[0009] As described above, the protective layer of a high-melting
point dielectric must be durable against repeated thermal stress
caused by the heating and cooling, must not allow such thermal
effect to influence the reflective film or other areas, and it is
also required to be thin, of low reflectivity, and of strong
resistivity against deterioration. From this perspective, the
dielectric protective layer plays an important role.
[0010] Generally speaking, although a phase change optical disk
such as a DVD-RAM guarantees the number of rewritings 10.sup.5 to
10.sup.6 times, there are problems of the rewriting characteristics
deteriorating as a result of S or the like diffusing from the zinc
sulfide-silicon oxide (ZnS--SiO.sub.2) layer used for protecting
the foregoing recording layer.
[0011] As a method of overcoming this problem, an intermediate
layer is being provided between the recording layer and protective
layer, and, in particular, GeCrN materials are being proposed as
the material for such intermediate layer.
[0012] Upon forming a GeCrN intermediate layer, a Ge--Cr alloy
target is generally used, and reactive sputtering is performed in a
nitrogen gas atmosphere.
[0013] Nevertheless, with a conventional target, there was
deposition speed variation, and there were problems in that such
variation would trigger the deviation of the film composition,
which would result in defective products and deterioration of the
production yield.
[0014] As conventional technology, disclosed is technology which
uses Ge--Cr materials and the like, and a compositional
discontinuous face orthogonal to the thickness direction is set,
and the space between the upper face, which is the face on the side
in which sputtering is started, and the compositional discontinuous
face is defined as a first region. Moreover, for forming a thin
film containing a plurality of components in a desired ratio from
immediately after the start of use, the content of each component
in the 1st region is set in such a manner that the lower is the
sputtering rate of a component, the higher is its concentration as
compared with the desired ratio of the formed thin film (c.f.
Japanese Patent Laid-Open Publication No. 2000-178724).
[0015] Further, as a conventional Ge--Cr sputtering target,
disclosed is a sputtering target in which, when the X-ray
diffraction intensity is measured with the sputtering target, the
ratio of a peak intensity of (220) plane against a peak intensity
of (111) plane, (I.sub.220/I.sub.111), is 0.3 or more, and the
spread of the peak-intensity ratio I.sub.220/I.sub.111 on the whole
target-surface is within .+-.30% (cf, for example, Japanese Patent
Laid-Open Publication No. 2002-38258).
[0016] Moreover, as a conventional Ge--Cr sputtering target,
disclosed is a target in which the Ag content and the Au content in
the high-purity Ge or Ge alloy are each 5 ppm or below, and the
variation of the Ag content and Au content in the whole target are
each within 30% (cf., for example, Japanese Patent Laid-Open
Publication No. 2002-69624).
SUMMARY OF THE INVENTION
[0017] An object of the present invention is to provide a Ge--Cr
alloy sputtering target capable of suppressing the variation of the
deposition speed and film composition, as well as improving the
production yield, of the GeCrN layer deposited by reactive
sputtering as the intermediate layer between the recording layer
and protective layer of a phase-change optical disk, and the
manufacturing method of such a target.
[0018] In order to achieve the foregoing object, as a result of
intense study, the present inventors discovered that the variation
of the deposition speed and film composition can be suppressed and
the production yield can be improved by optimizing the conditions
of the target density, and the variation of the density and
composition.
[0019] Based on the foregoing discovery, the present invention
provides a Ge--Cr alloy sputtering target containing 5 to 50 at %
of Cr and having a relative density of 95% or more, or a relative
density of 97% or more. Preferably, the density variation in the
target is within .+-.1.5%; the composition variation in the target
is within .+-.0.5%; and in X-ray diffraction, the ratio B/A of the
maximum peak intensity A of Ge phase in a 2.theta. range of
20.degree. to 30.degree. and of the maximum peak intensity B of
GeCr compound phase in a 2.theta. range of 30.degree. to 40.degree.
is 0.18 or more.
[0020] The present invention also provides a method of
manufacturing a Ge--Cr alloy sputtering target comprising the steps
of evenly dispersing and mixing Cr powder of 75 .mu.m or less and
Ge powder of 250 .mu.m or less having a BET specific surface area
of 0.4 m.sup.2/g or less, and thereafter performing sintering
thereto. Preferably, the BET specific surface area of the Ge powder
is 0.1 to 0.4 m.sup.2/g, and sintering is performed under the
conditions of hot pressing at a sintering temperature of 760 to
900.degree. C. and a surface pressure of 75 to 250 kg/cm.sup.2. The
method can be used to produce a Ge--Cr alloy sputtering target
containing 5 to 50 at % of Cr and having: a relative density of 95%
or more, or 97% or more; a density variation in the target within
.+-.5%; a composition variation in the target within .+-.0.5%; and
in X-ray diffraction, a ratio B/A of the maximum peak intensity A
of Ge phase in a 2.theta. range of 20.degree. to 30.degree. and of
the maximum peak intensity B of GeCr compound phase in a 2.theta.
range of 30.degree. to 40.degree. of 0.18 or more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a diagram (graph) showing the correlation of the
specific surface area of the Ge powder and the relative density (%)
of the GeCr target; and
[0022] FIG. 2 is a diagram (graph) showing the correlation of the
Cr grain size (minus sieve) and the relative density % of the GeCr
target.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The sputtering target of the present invention is
characterized in that a Ge--Cr alloy sputtering target containing 5
to 50 at % of Cr has a relative density of 95% or more, and further
a relative density of 97% or more.
[0024] This high density Ge--Cr alloy target can be manufactured by
evenly dispersing and mixing Cr powder of 75 .mu.m or less
(hereinafter referred to as the "75 .mu.m minus sieve" in this
Description) and Ge powder of 250 .mu.m or less (hereinafter
referred to as the "250 .mu.m minus sieve" in this Description)
having a BET specific surface area of 0.4 m.sup.2/g or less,
preferably 0.3 m.sup.2/g or less, and thereafter performing
sintering thereto.
[0025] This kind of high density Ge--Cr alloy target suppresses the
variation of the deposition speed and film composition of the GeCrN
thin film formed by reactive sputtering, and significantly reduces
the generation of defective products.
[0026] The GeCrN thin film formed as described above is extremely
effective as an intermediate layer between the recording layer and
protective layer of the phase change optical disk.
[0027] The relationship of the specific surface area of the Ge
powder and the relative density (%) of the GeCr target is shown in
FIG. 1. Further, the relationship of the Cr grain size and the
relative density (%) of the GeCr target is shown in FIG. 2. These
are correlation diagrams of the target when using the minus sieve
of the respective powders.
[0028] Further, these are each of Ge-20 at % Cr and subject to hot
pressing under the conditions 800.degree. C..times.150
kg/cm.sup.2.
[0029] If the relative density of the Ge--Cr alloy sputtering
target is less than 95%, variation of the deposition speed and film
composition will increase, and the production yield will
deteriorate.
[0030] Moreover, if Cr powder exceeding the 75 .mu.m minus sieve
and Ge powder exceeding the 250 .mu.m minus sieve and exceeding the
BET specific surface area of 0.4 m.sup.2/g are used for sintering,
a relative density of 95% or more cannot be attained, and,
similarly, the variation of the deposition speed and film
composition will increase, and the production yield will
deteriorate.
[0031] Further, it is preferable that the density variation of the
Ge--Cr alloy sputtering target is within .+-.1.5%, and more
preferable that the composition variation of the target is within
.+-.0.5%. As a result, the variation of the deposition speed and
film composition can be further suppressed.
[0032] A GeCr compound phase and a Ge phase exist in the Ge--Cr
alloy sputtering target, and it is desirable that, in the X-ray
diffraction, the ratio B/A of the maximum peak intensity A of Ge
phase in a 2.theta. range of 20.degree. to 30.degree. and of the
maximum peak intensity B of GeCr compound phase in a 2.theta. range
of 30.degree. to 40.degree. is 0.18 or more. As a result, the
uniformity can be further improved.
[0033] Upon manufacturing a Ge--Cr alloy sputtering target, it is
desirable to evenly disperse and mix Ge powder having a BET
specific surface area of 0.1 to 0.4 m.sup.2/g, and thereafter
performing sintering thereto.
[0034] Moreover, upon performing such sintering, it is desirable
that sintering is performed by hot pressing under the conditions of
a sintering temperature of 760 to 900.degree. C. and a surface
pressure of 75 to 250 kg/cm.sup.2.
[0035] As a result, Ge--Cr alloy sputtering target having a further
stable relative density of 95% or more can be manufactured
thereby.
[0036] Since the increase in density of the sputtering target
reduces pores and miniaturizes the crystal grains, and thereby
makes the sputtering face of the target even and smooth, a
significant effect is yielded in that the formation of particles
and nodules during sputtering can be suppressed and the target life
can be prolonged.
EXAMPLES AND COMPARATIVE EXAMPLES
[0037] The present invention is now described with reference to the
Examples and Comparative Examples. These Examples are merely
illustrative, and the present invention shall in no way be limited
thereby. In other words, the present invention shall only be
limited by the scope of claim for a patent, and shall include the
various modifications other than the Examples of this
invention.
Example 1
[0038] Ge powder having a purity of 5N (99.999%) and minus sieve of
100 .mu.m and Cr powder having a purity of 3N (99.9%) and a minus
sieve of 55 .mu.M were prepared, mixed so as to obtain Ge-20 at %
Cr, and, filled in a carbon die after performing dry blending, and
hot-pressed under the conditions of a temperature of 800.degree. C.
and pressure of 150 kg/cm.
[0039] This sintered body was subject to finish processing to form
a target. The relative density of the target was 99% (5.54
g/cm.sup.3 at 100% density). The density of samples arbitrarily
extracted from three locations of the target was measured with the
Archimedes method. The results are shown in Table 1.
[0040] Similarly, the composition of samples arbitrarily extracted
from three locations of the target was analyzed. The results are
shown in Table 2. Further, the results of measuring the X-ray
diffraction intensity are shown in Table 3 for the surface of the
bulk sample cut from the target, said sample surface being faced
against substrate.
[0041] Next, reactive sputtering was performed with this target
under a nitrogenous argon atmosphere (Ar: N.sub.2=25:50 sccm) and
power of 200 W, and a GeCrN film having a thickness of 300 o was
formed on a substrate. The measurement results of the variation of
film thickness and permeability are shown in Table 4 and Table 5,
respectively. TABLE-US-00001 TABLE 1 Density Variation and XRD
Intensity Sample Density Example 1 99.0% 98.7% 99.4% Example 2
95.5% 96.0% 97.0% Example 3 98.8% 99.5% 99.2% Comparative Example 1
88.0% 90.2% 92.0% Comparative Example 2 90.3% 95.2% 92.0%
[0042] TABLE-US-00002 TABLE 2 Variation in Composition Sample
Composition Example 1 19.6% 20.2% 19.8% Example 2 19.7% 20.4% 19.9%
Example 3 50.2% 49.6% 50.2% Comparative Example 1 19.9% 18.9% 20.6%
Comparative Example 2 19.7% 21.5% 19.2%
[0043] TABLE-US-00003 TABLE 3 XRD Intensity Ratio Sample B/A
Example 1 0.24 Example 2 0.31 Comparative Example 1 0.10
Comparative Example 2 0.16
[0044] TABLE-US-00004 TABLE 4 Film Thickness (nm) Sample 1 2 3 4 5
6 7 8 9 Average .SIGMA. Example 1 290 325 295 315 330 310 285 290
290 303.3 17.0 Example 2 290 315 300 300 325 310 280 305 285 301.1
14.5 Example 3 285 320 280 315 335 320 275 310 290 303.3 21.2
Comparative 300 330 280 360 355 320 280 315 260 311.1 34.3 Example
1 Comparative 315 295 260 350 345 275 325 255 265 298.3 36.8
Example 2
[0045] TABLE-US-00005 TABLE 5 Permeability (%) 630 nm Sample A B C
D Average .SIGMA. Example 1 78.5 78.4 77.6 77.6 78.0 0.5 Example 2
79.0 78.8 78.2 77.9 78.5 0.5 Example 3 50.2 49.5 51.3 50.5 50.4 0.7
Comparative Example 1 79.2 73.2 74.3 84.1 77.7 5.0 Comparative
Example 2 77.2 84.5 76.5 84.1 80.6 4.3
Example 2
[0046] Ge powder having a purity of 5N (99.999%) and minus sieve of
200 .mu.m and Cr powder having a purity of 3N (99.9%) and a minus
sieve of 55ptm were prepared, mixed so as to obtain Ge-20 at % Cr,
filled in a carbon die after performing dry blending, and
hot-pressed under the conditions of a temperature of 800.degree. C.
and pressure of 100 kg/cm.sup.2.
[0047] This sintered body was subject to finish processing to form
a target. The relative density of the target was 96% (5.54
g/cm.sup.3 at 100% density). The density of samples arbitrarily
extracted from three locations of the target was measured with the
Archimedes method. The results are shown in Table 1.
[0048] Similarly, the composition of samples arbitrarily extracted
from three locations of the target was analyzed. The results are
shown in Table 2. Further, the results of measuring the X-ray
diffraction intensity are shown in Table 3 for the surface of the
bulk sample cut from the target, said sample surface being faced
against substrate.
[0049] Next, reactive sputtering was performed with this target
under a nitrogenous argon atmosphere (Ar: N.sub.2=25:50 sccm) and
power of 200 W, and a GeCrN film having a thickness of 300 .ANG.
was formed on a substrate. The measurement results of the variation
of film thickness and permeability are shown in Table 4 and Table
5, respectively.
Example 3
[0050] Ge powder having a purity of 5N (99.999%) and minus sieve of
75 .mu.m and Cr powder having a purity of 3N (99.9%) and a minus
sieve of 25 .mu.m were prepared, mixed so as to obtain Ge-50 at %
Cr, filled in a carbon die after performing dry blending, and
hot-pressed under the conditions of a temperature of 800.degree. C.
and pressure of 150 kg/cm.sup.2.
[0051] This sintered body was subject to finish processing to form
a target. The relative density of the target was 97%
(5.97g/cm.sup.3 at 100% density). The density of samples
arbitrarily extracted from three locations of the target was
measured with the Archimedes method. The results are shown in Table
1.
[0052] Similarly, the composition of samples arbitrarily extracted
from three locations of the target was analyzed. The results are
shown in Table 2. Further, the results of measuring the X-ray
diffraction intensity are shown in Table 3 for the surface of the
bulk sample cut from the target, said sample surface being faced
against substrate.
[0053] Next, reactive sputtering was performed with this target
under a nitrogenous argon atmosphere (Ar: N.sub.2=25:50 sccm) and
power of 200 W, and a GeCrN film having a thickness of 300 .ANG.
was formed on a substrate. The measurement results of the variation
of film thickness and permeability are shown in Table 4 and Table
5, respectively.
Comparative Example 1
[0054] Ge powder having a purity of 5N (99.999%) and minus sieve of
300 .mu.m and Cr powder having a purity of 3N (99.9%) and a minus
sieve of 150 .mu.m were prepared, mixed so as to obtain Ge-20 at %
Cr, filled in a carbon die after performing dry blending, and
hot-pressed under the conditions of a temperature of 800.degree. C.
and pressure of 50 kg/cm.sup.2.
[0055] This sintered body was subject to finish processing to form
a target. The relative density of the target was 90% (5.54
g/cm.sup.3 at 100% density). The density of samples arbitrarily
extracted from three locations of the target was measured with the
Archimedes method. The results are shown in Table 1.
[0056] Similarly, the composition of samples arbitrarily extracted
from three locations of the target was analyzed. The results are
shown in Table 2. Further, the results of measuring the X-ray
diffraction intensity are shown in Table 3 for the surface of the
bulk sample cut from the target, said sample surface being faced
against substrate.
[0057] Next, reactive sputtering was performed with this target
under a nitrogenous argon atmosphere (Ar: N.sub.2=25:50 sccm) and
power of 200 W, and a GeCrN film having a thickness of 300 .ANG.
was formed on a substrate. The measurement results of the variation
of film thickness and permeability are shown in Table 4 and Table
5, respectively.
Comparative Example 2
[0058] Ge powder having a purity of 5N (99.999%) and minus sieve of
350 .mu.m and Cr powder having a purity of 3N (99.9%) and a minus
sieve of 75 .mu.m were prepared, mixed so as to obtain Ge-20 at %
Cr, filled in a carbon die after performing dry blending, and hot
pressed under the conditions of a temperature of 750.degree. C. and
pressure of 100 kg/cm.sup.2.
[0059] This sintered body was subject to finish processing to form
a target. The relative density of the target was 93% (5.54
g/cm.sup.3 at 100% density). The density of samples arbitrarily
extracted from three locations of the target was measured with the
Archimedes method. The results are shown in Table 1.
[0060] Similarly, the composition of samples arbitrarily extracted
from three locations of the target was analyzed. The results are
shown in Table 2. Further, the results of measuring the X-ray
diffraction intensity are shown in Table 3 for the surface of the
bulk sample cut from the target, said sample surface being faced
against substrate.
[0061] Next, reactive sputtering was performed with this target
under a nitrogenous argon atmosphere (Ar: N.sub.2=25:50 sccm) and
power of 200 W, and a GeCrN film having a thickness of 300 .ANG.
was formed on a substrate. The measurement results of the variation
of film thickness and permeability are shown in Table 4 and Table
5, respectively.
[0062] As is evident from Examples 1 to 3 and Comparative Examples
1 and 2 shown in Table 1, the relative density of Examples 1 to 3
was each 95% or more, and, with respect to Example 1 and Example 3,
a relative density of 97% or more was attained. And in each of
these cases, the density variation in the target was within
.+-.1.5%.
[0063] Contrarily, the relative density of Comparative Example 1
and Comparative Example 2 was less than 95%, and the density
variation in the target exceeded .+-.1.5%.
[0064] As shown in Table 2, the composition variation in the target
of Examples 1 to 3 was each within .+-.0.5%.
[0065] Contrarily, the composition variation in the target of
Comparative Example 1 and Comparative Example 2 exceeded
.+-.0.5%.
[0066] Table 3 shows, for Examples 1 to 2 and Comparative Examples
1 and 2, the ratio B/A of maximum peak intensity A of Ge phase in a
2.theta. range of 20.degree. to 30.degree. and the maximum peak
intensity B of GeCr compound phase in a 2.theta. range of
30.degree. to 40.degree.. It is evident that Examples 1 to 2
satisfy the condition of the present invention, i.e. 0.18 or more.
However, with Comparative Examples 1 and 2, B/A was less than
0.18.
[0067] The evaluation results of the variation of the film
thickness and transmittance for the target having the foregoing
characteristics are shown in Table 4. It is evident that the
variation of the film thickness and transmittance in Examples 1 to
3 is significantly small. Contrarily, the variation of the film
thickness and transmittance in Comparative Examples 1 and 2 is
significantly large, and is not suitable for a target.
[0068] Moreover, the high density sputtering target of the present
invention is able to suppress the formation of particles and
nodules which take place during sputtering, and has an effect of
improving the film thickness uniformity. Contrarily, since the
density was low in the targets of Comparative Examples 1 and 2,
abnormal discharge occurred during sputtering, and consequently
there was a problem of increase in the formation of particles
(dust) and nodules.
[0069] Accordingly, it is evident that the sputtering target of the
present invention is extremely effective in forming a GeCrN layer
deposited by reactive sputtering as the intermediate layer between
the recording layer and protective layer of the phase change
optical disk.
[0070] When forming a GeCrN thin film by reactive sputtering
employing the high density Ge--Cr alloy sputtering target of the
present invention, the variation of the deposition speed and the
accompanying composition deviation can be effectively suppressed,
and a superior effect is yielded in that stable sputtering
characteristics can be obtained. As a result, the incidence rate of
defective products can be significantly reduced. Further, upon
sputtering, the generation of particles and nodules can be reduced,
and the film thickness uniformity can also be improved.
* * * * *