U.S. patent application number 10/883014 was filed with the patent office on 2005-02-10 for phase change recording film having high electric resistance and sputtering target for forming phase change recording film.
This patent application is currently assigned to Mitsubishi Materials Corporation. Invention is credited to Kinoshita, Kei, Mori, Satoru, Nonaka, Sohei.
Application Number | 20050031484 10/883014 |
Document ID | / |
Family ID | 33437005 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050031484 |
Kind Code |
A1 |
Nonaka, Sohei ; et
al. |
February 10, 2005 |
Phase change recording film having high electric resistance and
sputtering target for forming phase change recording film
Abstract
A phase change recording film having a high electrical
resistance is provided. The phase change recording film may have
the following composition in atom %: 15 to 30% of Ge, 15 to 25% of
Sb, a total of 0.1 to 13% of one or both of Al and Si, and the
balance of Te and impurities. Also, a sputtering target is provided
for forming a phase change recording film having a high electrical
resistance. The sputtering target may have the same composition as
described above for the phrase change recording film.
Inventors: |
Nonaka, Sohei; (Sanda-shi,
JP) ; Kinoshita, Kei; (Sanda-shi, JP) ; Mori,
Satoru; (Sanda-shi, JP) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Mitsubishi Materials
Corporation
Tokyo
JP
|
Family ID: |
33437005 |
Appl. No.: |
10/883014 |
Filed: |
July 1, 2004 |
Current U.S.
Class: |
420/579 ;
257/E45.002; G9B/7.014; G9B/7.142 |
Current CPC
Class: |
G11B 2007/24328
20130101; C23C 14/3414 20130101; G11B 7/00454 20130101; G11B 7/243
20130101; G11B 2007/2431 20130101; G11B 2007/24312 20130101; H01L
45/144 20130101; H01L 45/06 20130101; G11B 2007/24314 20130101;
H01L 45/1625 20130101 |
Class at
Publication: |
420/579 |
International
Class: |
C22C 028/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2003 |
JP |
2003-190746 |
Oct 3, 2003 |
JP |
2003-345360 |
Oct 3, 2003 |
JP |
2003-345361 |
Claims
What is claimed is:
1. A phase change recording film having a high electrical
resistance, the phase change recording film comprising, by atom %
15 to 30% of Ge; 15 to 25% of Sb; a total of 0.1 to 13% of one or
both of Al and Si; and the balance of Te and impurities.
2. A phase change recording film according to claim 1, wherein the
specific resistance is about 5.times.10.sup.-2 to 5.times.10.sup.1
.OMEGA..multidot.cm.
3. A sputtering target for forming the phase change recording film
having a high electrical resistance, the sputtering target
comprising: to 30% of Ge; to 25% of Sb; a total of 0.1 to 13% of
one or two elements selected from the group consisting essentially
of Al and Si; and the balance of Te and impurities.
4. A phase change recording film having a high electrical
resistance, the phase change recording film comprising, by atom %
15 to 30% of Ge; 15 to 30% of Sb; 0.2 to 8% of C; and the balance
of Te and impurities.
5. A phase change recording film according to claim 4, wherein the
specific resistance is about 5.times.10.sup.-2 to 5.times.10.sup.1
.OMEGA..multidot.cm.
6. A sputtering target for forming the phase change recording film
having a high electrical resistance, the sputtering target
comprising: to 30% of Ge; to 30% of Sb; 0.2 to 8% of C; and the
balance of Te and impurities.
7. A phase change recording film having a high electrical
resistance, the phase change recording film comprising, by atom %
15 to 30% of Ge; 15 to 30% of Sb; 0.2 to 12% of B; and the balance
of Te and impurities.
8. A phase change recording film according to claim 7, wherein the
specific resistance is about 5.times.10.sup.-2 to 5.times.10.sup.1
.OMEGA..multidot.cm.
9. A sputtering target for forming the phase change recording film
having a high electrical resistance, the sputtering target
comprising: to 30% of Ge; to 30% of Sb; 0.2 to 12% of B; and the
balance of Te and impurities.
10. A sputtering target for forming the phase change recording film
having a high electrical resistance, the sputtering target
comprising: to 30% of Ge; to 30% of Sb; a total of 0.1 to 10% of at
least one or two elements selected from the group consisting
essentially of Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb
and Lu, and the balance of Te and impurities.
11. A phase change recording film having a high electrical
resistance, the phase change recording film comprising: to 30% of
Ge; to 30% of Sb; a total of 0.1 to 10% of at least one or two
elements selected from the group consisting essentially of Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and the balance
of Te and impurities.
12. A phase change recording film according to claim 11, wherein
the specific resistance is 5.times.10.sup.-2 to 5.times.10.sup.1
.OMEGA..multidot.cm.
Description
INCORPORATION BY REFERENCE
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to Japanese Patent Application Nos. 2003-190746 filed on
Jul. 3, 2003; 2003-345360 filed on Oct. 3, 2003 and 2003-345361
filed on Oct. 3, 2003. The contents of the applications are
incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a phase change recording
film having a high electrical resistance and a sputtering target
for forming the phase change recording film.
[0004] 2. Description of the Related Art
[0005] Generally, a Ge--Sb--Te system recording material is used
for a phase change recording layer for a phase change memory (Phase
Change RAM which is a kind of a semiconductor non-volatile memory).
In this phase change recording layer, a crystalline phase change
material is used, and a part of the phase change material is
rapidly heated and melted by a heater, thereby carrying out
rewriting. That is, the phase change material is rapidly cooled and
then is made partially amorphous, or an amorphous substance of the
phase change material is kept at the temperature that is over its
crystallization temperature and below its melting point to return
it to a crystalline state, thereby carrying out rewriting. Thus,
reading is performed by means of a difference between the electric
resistance of the crystalline phase change material, and that of
the partially amorphous phase change material. It is known that
this phase change recording layer is formed by sputtering using a
target comprising alloys having the composition to be a phase
change recording layer (for example, referred to patent documents 1
to 3: JP 2001-502848 bulletin, JP 2002-512439 bulletin, and JP
2002-540605 bulletin, respectively, and, Non-patent document 1 and
2: "A monthly publication of The Japan Society of Applied Physics"
Vol. 71, No.12 (2002) Page 1513-1517, and "Nikkei Micro-devices"
March, 2002 Page 70-78, respectively).
[0006] However, mentioned in Non-patent document 1, a conventional
phase change recording film still has a problem to be realized in
micro-fabrication, because of the large electric current in a
circuit at the time of writing and erasing, which consequently
increases the power consumption. As such, these reasons
collectively put a burden on a circuit.
[0007] Thus, a phase change memory chip having a small electric
current at the time of writing and erasing operation is under
development to be utilized in a phase change recording layer which
requires a small electric current at the time of writing and
erasing operation.
SUMMARY OF THE INVENTION
[0008] Thus, the present inventors have studied to decrease the
electric current at the time of writing and erasing operation, by
increasing the electrical resistance of a phase change recording
film.
[0009] As a result, in a Ge--Sb--Te system phase change recording
film, a phase change recording film containing, by atom %
(hereinafter, % means atom %), a total of 0.1 to 13% of one or two
elements selected from the group consisting essentially of Al and
Si has a high electrical resistance in a crystalline state, and by
means of the improvement, which makes it possible to reduce the
electric current at the time of writing and erasing operation.
[0010] A study showed that a Ge--Sb--Te system phase change
recording film containing a total of 0.1 to 13% of one or two
elements selected from the group consisting essentially of Al and
Si can be obtained by sputtering using a Ge--Sb--Te system target
containing a total of 0.1 to 13% of one or two elements selected
from the group consisting essentially of Al and Si.
[0011] The present invention, which is made based on the study
result, provides (1) a phase change recording film having a high
electrical resistance, wherein the phase change recording film has
a composition comprising, by atom % (hereinafter, % means atom %):
15 to 30% of Ge; 15 to 25% of Sb; a total of 0.1 to 13% of one or
two elements selected from the group consisting essentially of Al
and Si; and the balance of Te and inevitable impurities, (2) a
sputtering target for forming the phase change recording film
having a high electrical resistance described in (1), wherein the
phase change recording film has a composition comprising: 15 to 30%
of Ge; 15 to 25% of Sb; a total of 0.1 to 13% of one or two
elements selected from the group consisting essentially of Al and
Si; and the balance of Te and inevitable impurities.
[0012] Further, in a Ge--Sb--Te system phase change recording film,
a phase change recording film containing 0.2 to 8% of C(carbon) by
atom % (hereinafter, % means atom %) has high electrical resistance
in a crystalline state, which makes it possible to reduce the
electric current at the time of writing and erasing operation.
[0013] A study showed that a Ge--Sb--Te system phase change
recording film containing 0.2 to 8% of C(carbon) could be obtained
by sputtering using a Ge--Sb--Te system target containing 0.2 to 8%
of C(carbon).
[0014] Therefore, the present invention provides a phase change
recording film having a high electrical resistance, wherein the
phase change recording film has a composition comprising, by atom %
(hereinafter, % means atom %): 15 to 30% of Ge; 15 to 30% of Sb;
0.2 to 8% of C(carbon); and the balance of Te and inevitable
impurities, and a sputtering target for forming the phase change
recording film having a high electrical resistance, wherein the
phase change recording film has a composition comprising: 15 to 30%
of Ge; 15 to 30% of Sb; 0.2 to 8% of C(carbon); and the balance of
Te and inevitable impurities.
[0015] Further, in a Ge--Sb--Te system phase change recording film,
a phase change recording film containing 0.2 to 12% of B(boron) by
atom % (hereinafter, % means atom %) has high electrical resistance
in a crystalline state, which makes it possible to reduce the
electric current at the time of writing and erasing operation.
[0016] A study showed that a Ge--Sb--Te system phase change
recording film containing 0.2 to 12% of B(boron) could be obtained
by sputtering using a Ge--Sb--Te system target containing 0.2 to
12% of B(boron).
[0017] Therefore, the present invention provides a phase change
recording film having a high electrical resistance, wherein the
phase change recording film has a composition comprising, by atom %
(hereinafter, % means atom %): 15 to 30% of Ge; 15 to 30% of Sb;
0.2 to 12% of B(boron); and the balance of Te and inevitable
impurities, and a sputtering target for forming the phase change
recording film having a high electrical resistance described (1),
wherein the phase change recording film has a composition
comprising: 15 to 30% of Ge; 15 to 30% of Sb; 0.2 to 12% of
B(boron); and the balance of Te and inevitable impurities.
[0018] Further, a study showed that a sputtering target utilized to
form a Ge--Sb--Te system phase change recording film containing a
lanthanoid element that has a larger atomic weight than La,
selected from lanthanoid elements having the similar property as
La, is stronger in mechanical strength. As a result, the film
showed a stronger resistance against crack during sputtering, and
exhibited less number of arcing. A sputtering target including Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu rather than
La is better in mechanical strength, and stronger against crack
during sputtering, and showed less number of arcing.
[0019] The present invention, which is made based on the study
result, provides a sputtering target for forming the phase change
recording film having a high electrical resistance, wherein the
phase change recording film has a composition comprising: 15 to 30%
of Ge; 15 to 30% of Sb; a total of 0.1 to 10% of at least one or
two elements selected from the group consisting essentially of Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and the
balance of Te and inevitable impurities.
[0020] When sputtering is performed using a sputtering target for
forming the phase change recording film described above, a phase
change recording film having a high electrical resistance can be
obtained wherein the film has a composition comprising: 15 to 30%
of Ge; 15 to 30% of Sb; a total of 0.1 to 10% of at least one or
two elements selected from the group consisting essentially of Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and the
balance of Te and inevitable impurities.
[0021] Therefore, the present invention provides a phase change
recording film having a high electrical resistance, wherein the
phase change recording film has a composition comprising: 15 to 30%
of Ge; 15 to 30% of Sb; a total of 0.1 to 10% of at least one or
two elements selected from the group consisting essentially of Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and the
balance of Te and inevitable impurities.
[0022] Herein below, the reason why the composition of a sputtering
target for forming a phase change recording film according to the
present invention, and a phase change recording film having a high
electrical resistance that is formed using the sputtering target is
limited as described above, will be explained.
[0023] (a) Al and Si
[0024] If the content of these elements contained in a phase change
recording film is less than 0.1%, it is not preferable because the
resistance value of the film does not significantly increase. On
the other hand, if the content exceeds 13%, it is also not
preferable because the crystallization temperature rises too high.
Hence, the total content of one or two elements selected from the
group consisting essentially of Al and Si is set to about 0.1 to
13%.
[0025] If the crystallization temperature rises suitably, it can be
expected that the stability of amorphous state increases and
retention characteristics be improved in case that the film is used
as a memory. However, if the temperature is too high,
crystallization becomes difficult. Therefore, the total content of
one or two elements selected from the group of consisting
essentially of Al and Si is more preferably set to about 1 to 10%
(more preferably set to about 1 to 8%).
[0026] (b) C(carbon)
[0027] If the content of carbon element contained in a phase change
recording film is less than 0.2%, it is not preferable because the
resistance value of the film does not significantly increase. On
the other hand, if the content exceeds 8%, it is also not
preferable because the crystallization temperature rises too high.
Hence, the total content of carbon element is set to about 0.2 to
8%.
[0028] If the crystallization temperature rises suitably, it can be
expected that the stability of amorphous state increases and
retention characteristics be improved in case that the film is used
as a memory. However, if the temperature is too high,
crystallization becomes difficult. Therefore, the total content of
C(carbon) element is more preferably set to about 0.5 to 6%.
[0029] (c) B(boron)
[0030] If the crystallization temperature rises suitably, it can be
expected that the stability of amorphous state increases and
retention characteristics be improved in case that the film is used
as a memory. However, if the temperature is too high,
crystallization becomes difficult. From the reasons described
above, if the content of boron element contained in a phase change
recording film is less than 0.2%, it is not preferable because the
resistance value of the film does not significantly increase. On
the other hand, if the content exceeds 12%, it is also not
preferable because the crystallization temperature rises too high.
Hence, the content of boron element contained in the phase change
recording film of the present invention is set to about 0.2 to 12%.
The content of boron element contained in the phase change
recording film of the present invention is more preferably set to
about 1.0 to 10.0%.
[0031] (d) At least one or two elements selected from the group
consisting essentially of Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho,
Er, Tm, Yb and Lu:
[0032] If other lanthanoid element including La is added to a phase
change recording film, the resistance value of the phase change
recording film increase. However, if Ce, Pr, Nd, Pm, Sm, Eu, Gd,
Tb, Dy, Ho, Er, Tm, Yb and Lu rather than La is added to a
sputtering target for forming a phase change recording film, the
mechanical strength increases, the crack during sputtering
decreases, and particles are less generated. Thus, at least one or
two elements selected from the group consisting essentially of Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu is and/or are
added to a sputtering target for forming the Ge--Sb--Te system
phase change recording film according to the present invention.
However, if the content of elements contained in a phase change
recording film is less than 0.1%, it is not preferable because the
resistance value of the film does not significantly increase. On
the other hand, if the content exceeds 10%, it is also not
preferable because the crystallization temperature rises too
high.
[0033] Hence, the total content of at least one or two elements
selected from the group consisting essentially of Ce, Pr, Nd, Pm,
Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu included in a sputtering
target for forming a phase change recording film of the present
invention is set to about 0.1 to 10%. The content of these elements
is more preferably set to about 1 to 8%.
[0034] In addition, setting the total content of at least one or
two elements selected from the group consisting essentially of Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, to about 0.1
to 10%, is based on the following reasons. That is, the optimized
rising of crystallization temperature in a phase change recording
film means the stabilization of amorphous state, and a memory
having excellent retention characteristics for a long time can be
obtained. However, if the total content of at least one two
elements selected from the group consisting essentially of Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu is less than
0.1%, the crystallization temperature does not rises optimally. On
the other hand, if the total content of an element(s) exceeds 10%,
the temperature for crystallization is so high that a large amount
of electricity is required for rewriting in a memory, which is not
preferable from the viewpoint of low power consumption.
[0035] (e) Ge and Sb
[0036] It is preferable that Ge and Sb in the phase change
recording film having a high electrical resistance included Al
and/or Si are in a range of 15 to 30% of Ge and 15 to 25% of Sb.
Setting the range like that is based on the following reasons. That
is, if the content of Ge is less than 15% or the content of Sb is
less than 15%, and if the content of Ge exceeds 30% or the content
of Sb exceeds 25%, the resistance value decreases, and the time
required for crystallization becomes long, which is not
preferable.
[0037] It is preferable that Ge and Sb in the phase change
recording film having a high electrical resistance included
C(carbon), B(boron) or At least one or two elements selected from
the group consisting essentially of Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb and Lu are in a range of 15 to 30% of Ge and 15
to 25% of Sb. Setting the range like that is based on the following
reasons. That is, if the content of Ge is less than 15% or the
content of Sb is less than 15%, and if the content of Ge exceeds
30% or the content of Sb exceeds 30%, the resistance value
decreases, and the time required for crystallization becomes long,
which is not preferable.
[0038] The content of Ge and Sb are more preferably set to about 17
to 25% of Ge, about 17 to 23% of Sb. In the phase change recording
film having a high electrical resistance according to the present
invention, it is preferable that the specific resistance value
measured by the four point probe method after crystallization be
more than 5.times.10.sup.-2 .OMEGA..multidot.cm (it is more
preferable that the specific resistance value be not less than
8.times.10.sup.-2 .OMEGA..multidot.cm). The reason is as follows.
If the specific resistance value is less than 5.times.10.sup.-2
.OMEGA..multidot.cm, a large amount of electric current in a
circuit, the power consumption becomes large, and a problem to be
realized in micro-fabrication occurs, which are not preferable.
Further, the specific resistance of a Ge--Sb--Te alloy in an
amorphous state is about 1.times.10.sup.3 .OMEGA..multidot.cm, and
it is preferable for stable reading that the difference between the
specific resistance values of a phase change recording film in a
crystalline state and an amorphous state is at least one and half
order. Therefore, it is necessary that the specific resistance
value of a phase change recording film in the crystallized state is
less than 5.times.10.sup.1 .OMEGA..multidot.cm. Thus, the specific
resistance value measured by the four point probe method after
crystallization of the phase change recording film according to the
present invention is set to 5.times.10.sup.-2 to 5.times.10.sup.1
.OMEGA..multidot.cm.
[0039] A sputtering target for forming a phase change recording
film according to the present invention is prepared by a method
comprising the steps of: melting an alloy having the same
composition as the phase change recording film according to the
present invention in an Ar gas atmosphere; tapping the melt into an
iron mold to form an alloy ingot; pulverizing the ingot into alloy
powder in an inert gas atmosphere; and finally hot-pressing the
alloy powder in vacuum. More, it is also possible to make a sputter
target by hot-pressing a powder mixed a Ge--Sb--Te alloy powder and
a powder of Al, Si, C, B, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho,
Er, Tm, Yb and Lu. The hot pressing in vacuum is performed under a
pressure of 15 to 155 Mpa at a temperature of 370 to 580.degree. C.
for one or two hours. It is more preferable that, when the
temperature of the mold falls down to 270 to 300.degree. C., it is
cooled at normal temperature at a cooling rate of 1 to 3.degree.
C./min.
DESCRIPTION OF THE PREFERRED EMBODIMENT
EXAMPLE 1
[0040] Ge, Sb, Te and Al and/or Si were melted in an Ar gas
atmosphere, and the melt was cast to make an alloy ingot.
Thereafter, the ingot was crushed into alloy powder in an Ar
atmosphere, having a particle size less than or equal to 250
.mu.m.
[0041] The alloy powder was hot-pressed in vacuum under a pressure
of 146 Mpa at a temperature of 400.degree. C. to form a hot pressed
body. The hot pressed body was ground by a cemented carbide bit at
200 rpm lathe revolution to obtain a disc having 125 mm in diameter
and 5 mm in thickness. Targets 1 to 36 according to the present
invention, comparative targets 1 to 10 and a conventional target 1,
were prepared in this manner and the composition is shown in Table
1.
1 TABLE 1 Composition (atom %) Target Ge Sb Al Si Te The present 1
21.98 21.98 0.15 -- Balance invention 2 21.96 21.96 0.2 -- Balance
3 21.89 21.89 0.5 -- Balance 4 21.78 21.78 1.0 -- Balance 5 21.56
21.56 2.0 -- Balance 6 21.34 21.34 3.0 -- Balance 7 21.12 21.12 4.0
-- Balance 8 21.98 21.98 -- 0.15 Balance 9 21.96 21.96 -- 0.2
Balance 10 21.89 21.89 -- 0.5 Balance 11 21.78 21.78 -- 1.0 Balance
12 21.56 21.56 -- 2.0 Balance 13 21.34 21.34 -- 3.0 Balance 14
21.12 21.12 -- 4.0 Balance 15 21.34 21.34 1.0 2.0 Balance 16 21.34
21.34 2.0 1.0 Balance 17 21.09 21.09 4.8 -- Balance 18 20.65 20.65
6.7 -- Balance 19 20.42 20.42 8.2 -- Balance 20 19.98 19.98 9.8 --
Balance 21 19.78 19.78 11.2 -- Balance 22 19.31 19.31 12.9 --
Balance 23 21.09 21.09 -- 4.9 Balance 24 20.87 20.87 -- 5.6 Balance
25 21.98 21.98 -- 6.6 Balance 26 21.96 21.96 -- 7.9 Balance 27
21.89 21.89 -- 8.4 Balance 28 21.78 21.78 -- 9.1 Balance 29 21.56
21.56 -- 10.8 Balance 30 21.34 21.34 -- 12.6 Balance 31 21.12 21.12
0.5 0.2 Balance 32 21.98 21.98 1.3 0.2 Balance 33 21.96 21.96 0.9
4.5 Balance 34 21.89 21.89 5.8 1.0 Balance 35 21.78 21.78 3.6 6.2
Balance 36 21.56 21.56 8.1 4.0 Balance Comparative 1 21.99 21.99
0.05* -- Balance 2 18.87 18.87 15* -- Balance 3 21.99 21.99 --
0.05* Balance 4 18.87 18.87 -- 15* Balance 5 14.11* 24.80 10 --
Balance 6 31.23* 20.45 -- 10 Balance 7 23.50 14.10* 3.0 5.0 Balance
8 19.70 26.3* 6.0 1.0 Balance Conventional 1 22.20 22.20 -- --
Balance *mark means that the value deviates from the conditions of
the present invention.
[0042] Each of targets 1 to 36 according to the present invention,
comparative targets 1 to 10 and conventional target 1, was bonded
to a backing plate for cooling made of copper with an indium
bonding material of purity: 99.999 weight %, which was loaded into
a direct current magnetron sputtering apparatus, and the distance
between a target and a substrate (an Si wafer formed with SiO.sub.2
having 100 nm in thickness on the surface thereof) is set to be 70
mm. After vacuumizing was performed to reach an ultimate pressure
of less than or equal to 5.times.10.sup.-5 Pa, an Ar gas was
supplied to be a total pressure of 1.0 Pa. Under the conditions
of
[0043] Substrate temperature: room temperature,
[0044] Power input: 50 W (0.4 W/cm.sup.2),
[0045] sputtering was carried out to obtain the phase change
recording films 1 to 36 according to the present invention, the
comparative phase change recording films 1 to 8 and the
conventional phase change recording film 1 having the same
thickness of 300 nm on the surface of the substrate.
[0046] The composition of the phase change recording films 1 to 36
according to the present invention, the comparative phase change
recording films 1 to 8 and the conventional phase change recording
film 1 were measured by ICP (inductively coupled plasma method),
and the results are shown in Table 2. In addition, after the phase
change recording films 1 to 36 according to the present invention,
the comparative phase change recording films 1 to 8 and the
conventional phase change recording film 1, were kept for
crystallization at a temperature of 300.degree. C. for 5 minutes in
vacuum, the specific resistances thereof were measured by the four
point probe method. In addition, under the same conditions as
described above, a film was formed on the polycarbonate substrate
having 120 mm in diameter and 3 .mu.m in thickness. The coated film
was completely peeled off and powdered, and the crystallization
temperature was measured by DTA (Differential Thermal Analysis
Method) under the conditions which temperature rose to at a rate of
10.degree. C./min and argon gas was supplied at a rate of 200
ml/min. The results of the measurement are shown in Table 2. In
addition, the amounts of the samples used for this measurement were
all the same 20 mg. Here, the exothermic peak appearing in the
vicinity of 150 to 350.degree. C. is regarded as the
crystallization temperature.
2 TABLE 2 Specific Crystallization Phase change Composition (atom
%) Resistance temperature recording film Ge Sb Al Si Te (.OMEGA.
.multidot. cm) (.degree. C.) The 1 21.30 21.39 0.12 -- Balance 5.22
.times. 10.sup.-2 160.4 present 2 21.00 21.34 0.18 -- Balance 5.94
.times. 10.sup.-2 163.8 invention 3 20.13 21.32 0.49 -- Balance
7.69 .times. 10.sup.-2 167.3 4 20.03 21.17 0.79 -- Balance 8.32
.times. 10.sup.-2 177.6 5 20.80 20.96 1.94 -- Balance 9.54 .times.
10.sup.-2 197.5 6 19.65 20.79 2.92 -- Balance 1.12 .times.
10.sup.-1 215.3 7 17.44 20.50 3.96 -- Balance 1.65 .times.
10.sup.-1 238.4 8 20.22 21.37 -- 0.11 Balance 5.63 .times.
10.sup.-2 160.4 9 21.21 21.30 -- 0.16 Balance 6.25 .times.
10.sup.-2 163.4 10 21.15 21.19 -- 0.42 Balance 8.08 .times.
10.sup.-2 168.1 11 20.02 21.18 -- 0.90 Balance 9.86 .times.
10.sup.-2 178.8 12 19.83 20.92 -- 1.89 Balance 1.14 .times.
10.sup.-1 197.1 13 19.71 20.76 -- 2.85 Balance 1.49 .times.
10.sup.-1 218.9 14 20.37 20.45 -- 3.83 Balance 1.93 .times.
10.sup.-1 238.5 15 19.64 20.80 0.90 1.89 Balance 1.22 .times.
10.sup.-1 219.4 16 19.58 20.76 1.95 0.82 Balance 1.06 .times.
10.sup.-1 210.5 17 20.15 20.92 4.4 -- Balance 1.87 .times.
10.sup.-1 242.5 18 20.68 20.02 6.3 -- Balance 2.25 .times.
10.sup.-1 248.7 19 19.23 20.52 7.9 -- Balance 2.51 .times.
10.sup.-1 257.0 20 19.54 20.34 9.6 -- Balance 2.87 .times.
10.sup.-1 265.3 21 19.32 19.06 10.5 -- Balance 3.01 .times.
10.sup.-1 274.8 22 19.30 19.45 12.4 -- Balance 3.30 .times.
10.sup.-1 285.3 23 20.17 20.65 -- 4.5 Balance 2.04 .times.
10.sup.-1 241.6 24 20.65 20.41 -- 5.0 Balance 2.15 .times.
10.sup.-1 244.5 25 21.12 21.54 -- 6.3 Balance 2.24 .times.
10.sup.-1 247.2 26 21.39 21.82 -- 7.5 Balance 2.78 .times.
10.sup.-1 250.1 27 21.14 21.86 -- 8.0 Balance 2.91 .times.
10.sup.-1 252.3 28 21.54 21.37 -- 8.7 Balance 3.18 .times.
10.sup.-1 256.9 29 20.76 21.58 -- 10.6 Balance 3.94 .times.
10.sup.-1 265.7 30 21.04 21.37 -- 12.1 Balance 4.56 .times.
10.sup.-1 287.4 31 20.65 20.54 0.3 0.1 Balance 6.54 .times.
10.sup.-2 165.9 32 21.63 22.01 1.0 0.1 Balance 9.07 .times.
10.sup.-2 216.2 33 20.94 21.71 0.8 4.1 Balance 2.02 .times.
10.sup.-1 239.4 34 21.32 21.57 5.6 0.9 Balance 2.86 .times.
10.sup.-1 245.4 35 21.02 21.52 3.2 5.80 Balance 3.04 .times.
10.sup.-1 251.7 36 21.12 21.94 7.5 3.6 Balance 3.12 .times.
10.sup.-1 275.2 Comparative 1 20.25 21.39 0.04* -- Balance 3.62
.times. 10.sup.-2 159.8 2 18.18 18.88 14.65* -- Balance 8.13
.times. 10.sup.-1 350.7 3 19.97 21.40 -- 0.03* Balance 2.79 .times.
10.sup.-2 159.3 4 18.23 19.01 -- 14.51* Balance 1.07 .times.
10.sup.0 359.7 5 14.05* 24.61 9.4 -- Balance 4.82 .times. 10.sup.-2
268.9 6 31.21* 20.38 -- 9.1 Balance 4.69 .times. 10.sup.-2 271.6 7
23.39 14.0* 2.5 4.4 Balance 3.55 .times. 10.sup.-2 253.1 8 19.55
26.1* 5.6 0.5 Balance 3.76 .times. 10.sup.-2 241.6 Conventional 1
20.40 21.60 -- -- Balance 1.05 .times. 10.sup.-2 158.2 *mark means
that the value deviates from the conditions of the present
invention.
[0047] From the result shown in Tables 1 and 2, it can be
understood that the crystallized phase change recording films 1 to
36 according to the present invention which are obtained by
sputtering with the targets 1 to 36 according to the present
invention have a higher value in specific resistance than the
conventional crystallized phase change recording film 1 which are
obtained by sputtering with the conventional target 1. It can be
understood that the comparative crystallized phase change recording
films 1 to 8 which are obtained by sputtering with the comparative
targets 1 to 8 with the composition which is out of the range of
the present invention, have a lower specific resistance, or their
crystallization temperatures rise too much.
EXAMPLE 2
[0048] Ge, Sb and Te were melted in an Ar gas atmosphere, and the
melt was cast to form an alloy ingot. Thereafter, the ingot was
crushed into alloy powder in an Ar atmosphere, having a particle
size less than or equal to 250 .mu.m.
[0049] A commercially available carbon powder is mixed with the
alloy powder to make mixed powder. The mixed powder was hot-pressed
in vacuum under a pressure of 146 Mpa at a temperature of
400.degree. C. to form a hot pressed body. The hot pressed body was
ground by a cemented carbide bit at 200 rpm lathe revolution to
obtain a disc having 125 mm in diameter and 5 mm in thickness.
Targets 1 to 10 according to the present invention, comparative
targets 1 and 2, and the conventional target 1 were prepared and
the composition is shown in Table 3.
3 TABLE 3 Composition (atom %) Target Ge Sb C Te The present 1
21.98 21.98 0.25 Balance invention 2 21.89 21.89 0.6 Balance 3
21.82 21.82 0.9 Balance 4 21.78 21.78 1.10 Balance 5 21.56 21.56
2.15 Balance 6 21.34 21.34 3.00 Balance 7 20.90 20.90 5.00 Balance
8 20.68 20.68 6.00 Balance 9 20.65 20.65 7.00 Balance 10 20.10
20.10 8.00 Balance Comparative 1 21.99 21.99 0.1* Balance 2 20.24
20.24 10.00* Balance Conventional 1 22.20 22.20 -- Balance *mark
means that the value deviates from the conditions of the present
invention.
[0050] Each of targets 1 to 10 according to the present invention,
comparative targets 1 and 2 and conventional target 1, was
respectively bonded to a backing plate for cooling made of copper
with an indium bonding material of purity: 99.999 weight %, which
was loaded into a direct current magnetron sputtering apparatus,
and the distance between a target and a substrate (an Si wafer
formed with SiO.sub.2 having 100 nm in thickness on the surface
thereof) was set to be 70 mm. After vacuumizing was performed to
reach an ultimate pressure of less than or equal to
5.times.10.sup.-5 Pa, an Ar gas was supplied to be a total pressure
of 1.0 Pa. Under the conditions of
[0051] Substrate temperature: room temperature,
[0052] Power input: 50 W (0.4 W/cm.sup.2),
[0053] sputtering was carried out to obtain phase change recording
films 1 to 10 according to the present invention, comparative phase
change recording films 1 and 2 and a conventional phase change
recording film 1 having the same thickness of 300 nm on the surface
of the substrate.
[0054] The composition of the phase change recording films 1 to 10
according to the present invention, the comparative phase change
recording films 1 and 2 and the conventional phase change recording
film 1, were measured by EPMA (electron beam probe micro-analyzer),
and the results are shown in Table 4. On the other hand, influence
of C component introduced by surface absorption from the atmosphere
was considered in the composition analysis by EPMA. Therefore, the
value that the amount of carbon detected in the films which are
separately formed by using the Ge--Sb--Te target to which C is not
added (equivalent to amount of carbon adsorbed from the atmosphere)
is deducted from the analysis value of each film, is regarded as
the amount of carbon of each film. In addition, after the phase
change recording films 1 to 10 according to the present invention,
the comparative phase change recording films 1 and 2 and the
conventional phase change recording film 1, were kept for
crystallization at a temperature of 300.degree. C. for 5 minutes in
vacuum, the specific resistances thereof were measured by the four
point probe method. In addition, under the same conditions as
described above, a film was formed on the polycarbonate substrate
having 120 mm in diameter and 3 .mu.m in thickness. The coated film
was completely peeled off and powdered, and the crystallization
temperature was measured by DTA (Differential Thermal Analysis
Method) under the conditions which temperature rose to at a rate of
10.degree. C./min and argon gas was supplied at a rate of 200
ml/min. The results of the measurement are shown in Table 4. In
addition, the amounts of the samples used for this measurement were
all the same 15 mg. the exothermic peak appearing in the vicinity
of 150 to 350.degree. C. is regarded as the crystallization
temperature.
4 TABLE 4 Specific Crystallization Phase change Composition (atom
%) Resistance temperature recording film Ge Sb C Te (.OMEGA.
.multidot. cm) (.degree. C.) The 1 20.51 23.73 0.21 Balance 6.54
.times. 10.sup.-2 163.4 present 2 20.43 23.62 0.54 Balance 9.27
.times. 10.sup.-2 171.4 invention 3 20.34 23.58 0.81 Balance 1.40
.times. 10.sup.-1 178.2 4 20.30 23.49 1.02 Balance 1.81 .times.
10.sup.-1 182.9 5 20.11 23.26 1.97 Balance 2.53 .times. 10.sup.-1
207.5 6 19.93 22.57 2.93 Balance 3.32 .times. 10.sup.-1 234.3 7
19.45 22.57 4.90 Balance 4.84 .times. 10.sup.-1 254.5 8 19.24 22.38
5.86 Balance 5.77 .times. 10.sup.-1 263.2 9 20.14 20.56 6.60
Balance 6.34 .times. 10.sup.-1 284.4 10 19.34 20.25 7.41 Balance
7.50 .times. 10.sup.-1 292.8 Comparative 1 20.55 23.83 0.08*
Balance 3.42 .times. 10.sup.-2 161.2 2 18.83 21.81 9.82* Balance
1.03 .times. 10.sup.0 330.0 Conventional 1 20.40 21.60 -- Balance
1.05 .times. 10.sup.-2 158.2 *mark means that the value deviates
from the conditions of the present invention.
[0055] From the result shown in Tables 3 and 4, it can be
understood that the crystallized phase change recording films 1 to
10 according to the present invention which are obtained by
sputtering with the targets 1 to 10 according to the present
invention have a higher value in specific resistance than the
conventional crystallized phase change recording film 1 which are
obtained by sputtering with the conventional target 1. It can be
understood that the comparative crystallized phase change recording
films 1 and 2 which are obtained by sputtering with the comparative
targets 1 and 2 with the composition which is out of the range of
the present invention, have a lower specific resistance, or their
crystallization temperatures rise too much.
EXAMPLE 3
[0056] Ge, Sb, Te and B were melted in an Ar gas atmosphere, and
the melt was cast to form an alloy ingot. Thereafter, the ingot was
crushed into alloy powder in an Ar atmosphere, having a particle
size less than or equal to 250 .mu.m.
[0057] The alloy powder was hot-pressed in vacuum under a pressure
of 146 Mpa at a temperature of 400.degree. C. to form a hot pressed
body. The hot pressed body was ground by a cemented carbide bit at
200 rpm lathe revolution to obtain a disc having 125 mm in diameter
and 5 mm in thickness. Targets 1 to 9 according to the present
invention, comparative targets 1 and 2 and a conventional target 1,
were prepared in this manner and the composition is shown in Table
5.
5 TABLE 5 Composition (atom %) Target Ge Sb B Te The present 1
22.16 22.16 0.25 Balance invention 2 22.09 22.09 0.50 Balance 3
21.98 21.98 1.00 Balance 4 21.76 21.76 2.00 Balance 5 21.53 21.53
3.00 Balance 6 21.09 21.09 5.00 Balance 7 20.42 20.42 8.00 Balance
8 19.98 19.98 10.00 Balance 9 19.54 19.54 12.00 Balance Comparative
1 22.18 22.19 0.1* Balance 2 18.87 18.87 15.00* Balance
Conventional 1 22.20 22.20 -- Balance *mark means that the value
deviates from the conditions of the present invention.
[0058] Each of targets 1 to 9 according to the present invention,
comparative targets 1 and 2 and conventional target 1, was bonded
to a backing plate for cooling made of copper with an indium
bonding material of purity: 99.999 weight %, which was loaded into
a direct current magnetron sputtering apparatus, and the distance
between a target and a substrate (an Si wafer formed with SiO.sub.2
having 100 nm in thickness on the surface thereof) was set to be 70
nm. After vacuumizing was performed to reach an ultimate pressure
of less than or equal to 5.times.10.sup.-5 Pa, an Ar gas was
supplied to be a total pressure of 1.0 Pa. Under the conditions
of
[0059] Substrate temperature: room temperature,
[0060] Power input: 50 W (0.4 W/cm.sup.2),
[0061] sputtering was carried out to obtain phase change recording
films 1 to 9 according to the present invention, comparative phase
change recording films 1 and 2 and a conventional phase change
recording film 1 having thickness: 300 nm on the surface of the
substrate. The composition of the phase change recording films 1 to
9 according to the present invention, the comparative phase change
recording films 1 and 2 and the conventional phase change recording
film 1, which are obtained in this way, are analyzed by ICP
(inductively coupled plasma method), and the results are shown in
Table 6. In addition, after the phase change recording films 1 to 9
according to the present invention, the comparative phase change
recording films 1 and 2 and the conventional phase change recording
film 1, were kept for crystallization at a temperature of
300.degree. C. for 5 minutes in vacuum, the specific resistance
thereof were measured by the four point probe method. In addition,
under the same conditions as described above, a film was formed on
the polycarbonate substrate having 120 mm in diameter and 3 .mu.m
in thickness. The coated film was completely peeled off and
powdered, and the crystallization temperature was measured by DTA
(Differential Thermal Analysis Method) under the conditions which
temperature rose to at a rate of 10.degree. C./min and argon gas
was supplied at a rate of 200 ml/min. The results of the
measurement are shown in Table 6. In addition, the amounts of the
samples used for this measurement were all the same 15 mg. Here,
the exothermic peak appearing in the vicinity of 150 to 300.degree.
C. is regarded as the crystallization temperature.
6 TABLE 6 Specific Crystallization Phase change Composition (atom
%) Resistance temperature recording film Ge Sb B Te (.OMEGA.
.multidot. cm) (.degree. C.) The 1 22.44 23.16 0.21 Balance 5.08
.times. 10.sup.-2 160.8 present 2 20.41 23.10 0.46 Balance 5.54
.times. 10.sup.-2 163.9 invention 3 22.26 22.96 0.98 Balance 6.13
.times. 10.sup.-2 170.3 4 22.01 22.74 1.87 Balance 6.89 .times.
10.sup.-2 181.2 5 21.84 22.49 2.94 Balance 8.62 .times. 10.sup.-2
194.4 6 21.40 22.07 4.89 Balance 1.02 .times. 10.sup.-1 218.3 7
20.74 21.38 7.58 Balance 1.23 .times. 10.sup.-1 254.8 8 20.31 20.88
9.88 Balance 2.31 .times. 10.sup.-1 279.7 9 19.91 20.50 11.74
Balance 3.65 .times. 10.sup.-1 302.7 Comparative 1 22.49 23.22
0.04* Balance 3.25 .times. 10.sup.-2 158.7 2 19.05 19.72 14.96*
Balance 5.68 .times. 10.sup.-1 342.2 Conventional 1 20.40 21.60 --
Balance 1.05 .times. 10.sup.-2 158.2 *mark means that the value
deviates from the conditions of the present invention.
[0062] From the result shown in Tables 5 and 6, it can be
understood that the crystallized phase change recording films 1 to
9 according to the present invention which are obtained by
sputtering with the targets 1 to 9 according to the present
invention have a higher value in specific resistance than the
conventional crystallized phase change recording film 1 which are
obtained by sputtering with the conventional target 1. It can be
understood that the comparative crystallized phase change recording
films 1 and 2 which are obtained by sputtering with the comparative
targets 1 and 2 with the composition which is out of the range of
the present invention, have a lower specific resistance, or their
crystallization temperatures rise too much.
EXAMPLE 4
[0063] Ge, Sb and Te were melted in an Ar gas atmosphere, and the
melt was cast to form an alloy ingot. Thereafter, the ingot was
crushed into alloy powder in an Ar atmosphere, having a particle
size less than or equal to 100 .mu.m. The alloy powder and powders
of Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and La
with the particle size of less than or equal to 100 .mu.m, were
mixed to make mixed powder.
[0064] The mixed powder was hot-pressed in vacuum under a pressure
of 146 Mp at a temperature of 400.degree. C. to form a hot pressed
body. The hot pressed body was ground by a cemented carbide bit at
200 rpm lathe revolution to obtain a disc having 125 mm in diameter
and 5 mm in thickness. Targets 1 to 14 according to the present
invention, and a conventional target 1, were prepared in this
manner and the composition is shown in Table 7. In addition,
specimens of sintered bodies which are made under the same
conditions of making the targets 1 to 14 according to present
invention and the conventional target 1 are made, and the
three-point bending strength test to examine the strength of the
specimens based on a prescribed condition in JISR1601 is performed,
and the result is shown in Table 7.
[0065] Next, each of targets 1 to 14 according to the present
invention, and conventional target 1, was bonded to a backing plate
for cooling made of copper with an indium bonding material of the
purity of 99.999 weight %, which was loaded into a direct current
magnetron sputtering apparatus, and the distance between a target
and a substrate (an Si wafer formed with SiO.sub.2 having 100 nm in
thickness on the surface thereof) was set to be 70 mm. After
vacuumizing was performed to reach an ultimate pressure of less
than or equal to 5.times.10.sup.-5 Pa, an Ar gas was supplied to be
a total pressure of 1.0 Pa. Under the conditions of
[0066] Substrate temperature: room temperature,
[0067] Power input: 50 W (0.4 W/cm.sup.2),
[0068] sputtering was carried out to obtain phase change recording
films 1 to 14 according to the present invention, and a
conventional phase change recording film 1 having the same
thickness of 300 nm on the surface of the substrate, and at that
time, the times of arcing during sputtering and crack of the
targets after sputtering were observed. The result is shown in
Table 7.
7 TABLE 7 3 Point Composition (atom %) bending Lanthanoid strength
Times of Target Target Ge Sb Element Te (MPa) arcing crack The 1
21.87 21.87 Ce: 1.5 Balance 4.58 12 None present 2 21.87 21.87 Pr:
1.5 Balance 4.66 9 None invention 3 21.87 21.87 Nd: 1.5 Balance
4.79 6 None 4 21.87 21.87 Pm: 1.5 Balance 4.85 5 None 5 21.87 21.87
Sm: 1.5 Balance 4.92 5 None 6 21.87 21.87 Eu: 1.5 Balance 4.97 3
None 7 21.87 21.87 Gd: 1.5 Balance 5.07 2 None 8 21.87 21.87 Tb:
1.5 Balance 5.08 0 None 9 21.87 21.87 Dy: 1.5 Balance 5.12 0 None
10 21.87 21.87 Ho: 1.5 Balance 5.17 1 None 11 21.87 21.87 Er: 1.5
Balance 5.21 4 None 12 21.87 21.87 Tm: 1.5 Balance 5.25 2 None 13
21.87 21.87 Yb: 1.5 Balance 5.33 0 None 14 21.87 21.87 Lu: 1.5
Balance 5.43 3 None Conventional 1 21.87 21.87 La: 1.5 Balance 3.13
139 Yes
[0069] From the result shown in Table 7, it can be understood that
the three-point bending strength of the targets 1 to 14 having Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu added thereto
according to the present invention is higher than that of the
conventional target 1 having La added thereto so that mechanical
strength of the targets according to the present invention is
better. Also, among the targets 1 to 4 according to the present
invention, the bigger the atomic weight of the rare-earth elements
to be added is, the higher the three-point bending strength is. It
is considered the reason why the three-point bending strength of
the conventional target 1 is low is due to characteristics, such as
deliquescence or efflorescence, which are caused by atmospheric
moisture absorbed by La existing in the targets.
[0070] In addition, it can be understood that the present invention
targets 1 to 14 have fewer times of arcing, and a superior
resistibility against crack of the targets, compared with the
conventional target 1 having La added thereto.
[0071] The composition of the phase change recording films 1 to 14
according to the present invention, and the conventional phase
change recording film 1, were measured by ICP (inductively coupled
plasma method), and the results are shown in Table 8. In addition,
after the phase change recording films 1 to 14 according to the
present invention, and the conventional phase change recording film
1, were kept for crystallization at a temperature of 300.degree. C.
for 5 minutes in vacuum, the specific resistances thereof were
measured by the four point probe method. In addition, under the
same conditions as described above, a film was formed on the
polycarbonate substrate having 120 mm in diameter and 3 .mu.m in
thickness. The coated film was completely peeled off and powdered,
and the crystallization temperature was measured by DTA
(Differential Thermal Analysis Method) under the conditions which
temperature rose to at a rate of 10.degree. C./min and argon gas
was supplied at a rate of 200 ml/min. The results of the
measurement are shown in Table 8. In addition, the amounts of the
samples used for this measurement were all the same 15 mg. Here,
the exothermic peak appearing in the vicinity of 150 to 300.degree.
C. is regarded as the crystallization temperature.
8 TABLE 8 Composition (atom %) Specific Crystallization Phase
change Lanthanoid Resistance temperature recording film Ge Sb
Element Te (.OMEGA. .multidot. cm) (.degree. C.) The 1 22.17 22.46
Ce: 1.36 Balance 9.45 .times. 10.sup.-2 172.5 present 2 22.32 22.57
Pr: 1.44 Balance 9.88 .times. 10.sup.-2 178.3 invention 3 22.27
22.59 Nd: 1.37 Balance 9.60 .times. 10.sup.-2 173.6 4 22.36 22.65
Pm: 1.45 Balance 1.12 .times. 10.sup.-1 181.0 5 22.38 22.71 Sm:
1.40 Balance 1.01 .times. 10.sup.-1 177.3 6 22.25 22.58 Eu: 1.39
Balance 9.93 .times. 10.sup.-2 171.6 7 22.30 22.57 Gd: 1.44 Balance
1.08 .times. 10.sup.-1 179.8 8 22.38 22.59 Tb: 1.45 Balance 9.12
.times. 10.sup.-2 179.2 9 22.20 22.54 Dy: 1.44 Balance 9.97 .times.
10.sup.-2 176.0 10 22.22 22.61 Ho: 1.41 Balance 1.06 .times.
10.sup.-1 180.3 11 22.30 22.60 Er: 1.46 Balance 1.03 .times.
10.sup.-1 181.5 12 22.23 22.54 Tm: 1.38 Balance 9.16 .times.
10.sup.-2 173.7 13 22.33 22.64 Yb: 1.42 Balance 9.37 .times.
10.sup.-2 175.5 14 22.28 22.49 Lu: 1.48 Balance 1.10 .times.
10.sup.-1 182.7 Conventional 1 22.19 22.81 La: 1.43 Balance 9.89
.times. 10.sup.-2 171.8
[0072] From the result shown in Table 8, it can be understood that
the crystallized phase change recording films 1 to 14 according to
the present invention which are obtained by sputtering with the
targets 1 to 14 according to the present invention including the
same total amount of 0.1 and 10% of at least one or two elements
selected from the group consisting essentially of Ce, Pr, Nd, Pm,
Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu does not show substantial
difference in the values of specific resistance and crystallization
temperature compared with the conventional crystallized phase
change recording film 1 including La which are obtained by
sputtering with the conventional target 1 including La of same
amount, and both are the phase change recording films of a good
quality.
EXAMPLE 5
[0073] Ge, Sb and Te were melted in an Ar gas atmosphere, and the
melt was cast to form an alloy ingot. Thereafter, the ingot was
crushed into alloy powder in an Ar atmosphere, having a particle
size less than or equal to 100 .mu.m. The alloy powder and powders
of Tb with the particle size of less than or equal to 100 .mu.m,
were mixed to make mixed powder. The mixed powder was hot-pressed
in vacuum under a pressure of 146 Mpa at a temperature of
400.degree. C. to form makes the hot pressed body. The hot pressed
body was ground by a cemented carbide bit at 200 rpm lathe
revolution to obtain a disc having 125 mm in diameter and 5 mm in
thickness. Targets 15 to 24 according to the present invention, and
comparative targets 1 and 2, were prepared in this manner and the
composition is shown in Table 9.
9 TABLE 9 Composition (atom %) Target Ge Sb Tb Te The 15 22.18
22.18 0.15 Balance present 16 22.16 22.16 0.20 Balance invention 17
22.09 22.09 0.50 Balance 18 21.98 21.98 1.00 Balance 19 21.87 21.87
1.50 Balance 20 21.76 21.76 2.00 Balance 21 21.53 21.53 3.00
Balance 22 21.09 21.09 5.00 Balance 23 20.65 20.65 7.00 Balance 24
19.98 19.98 10.00 Balance Comparative 1 22.19 22.19 0.05* Balance 2
19.54 19.54 12.00* Balance *mark means that the value deviates from
the conditions of the present invention.
[0074] Next, each of targets 15 to 24 according to the present
invention, and comparative targets 1 and 2, was bonded to a backing
plate for cooling made of copper with an indium bonding materials
of indium material of the purity of 99.999 weight %, which was
loaded into a direct current magnetron apparatus, and the distance
between a target and a substrate (an Si wafer formed with SiO.sub.2
having 100 nm in thickness on the surface thereof) was set to be 70
mm. After vacuumizing was performed to reach an ultimate pressure
of less than or equal to 5.times.10.sup.-5 Pa, an Ar gas was
supplied to be a total pressure of 1.0 Pa. Under the conditions
of
[0075] Substrate temperature: room temperature,
[0076] Power input: 50 W (0.4 W/cm.sup.2),
[0077] sputtering was carried out to obtain phase change recording
films 15 to 24 according to the present invention, and phase change
recording films 1 and 2 having the same thickness of 300 nm on the
surface of the substrate.
[0078] The composition of the phase change recording films 15 to 24
according to the present invention, and the comparative phase
change recording films 1 and 2 were measured by ICP (inductively
coupled plasma method), and the results are shown in Table 10. In
addition, after the phase change recording films 15 to 24 according
to the present invention, and the comparative phase change
recording films 1 and 2, were kept for crystallization at a
temperature of 300.degree. C. for 5 minutes in vacuum, the specific
resistances thereof were measured by the four point probe method.
In addition, under the same conditions as described above, a film
was formed on the polycarbonate substrate having 120 mm in diameter
and 3 .mu.m in thickness. The coated film was completely peeled off
and powdered, and the crystallization temperature was measured by
DTA (Differential Thermal Analysis Method) under the conditions
which temperature rose to at a rate of 100 C/min and argon gas was
supplied at a rate of 200 ml/min. The results of the measurement
are shown in Table 10. In addition, the amounts of the samples used
for this measurement were all the same 15 mg. Here, the exothermic
peak appearing in the vicinity of 150 to 300.degree. C. is regarded
as the crystallization temperature.
10 TABLE 10 Specific Crystallization Phase change Composition (atom
%) Resistance temperature recording film Ge Sb Tb Te (.OMEGA.
.multidot. cm) (.degree. C.) The 15 23.02 23.13 0.11 Balance 5.21
.times. 10.sup.-2 159.6 present 16 22.95 23.08 0.17 Balance 5.89
.times. 10.sup.-2 161.5 invention 17 22.83 22.97 0.46 Balance 6.86
.times. 10.sup.-2 165.2 18 22.71 22.88 0.92 Balance 8.65 .times.
10.sup.-2 172.2 19 22.38 22.59 1.45 Balance 9.12 .times. 10.sup.-2
179.2 20 22.21 22.45 1.89 Balance 1.16 .times. 10.sup.-1 188.2 21
21.97 22.27 2.94 Balance 2.85 .times. 10.sup.-1 200.2 22 21.62
21.81 4.88 Balance 6.37 .times. 10.sup.-1 228.2 23 21.22 21.37 6.84
Balance 5.32 .times. 10.degree. 256.2 24 20.56 20.90 9.92 Balance
2.10 .times. 10.sup.1 298.2 Comparative 1 22.72 22.98 0.03* Balance
3.64 .times. 10.sup.-2 158.9 2 20.08 20.27 11.86* Balance 5.08
.times. 10.sup.1 326.2 *mark means that the value deviates from the
conditions of the present invention.
EXAMPLE 6
[0079] Ge, Sb and Te were melted in an Ar gas atmosphere, and the
melt was cast to form an alloy ingot. Thereafter, the ingot was
crushed into alloy powder in an Ar atmosphere, having a particle
size less than or equal to 100 .mu.alloy powder and powders of Dy
with the particle size of less than or equal to 100 .mu.m, were
mixed to make mixed powder. The mixed powder was hot-pressed in
vacuum a pressure of 146 Mpa at a temperature of 400.degree. C. to
form a hot pressed body. The hot pressed body was ground by a
cemented carbide bit at 200 rpm lathe revolution to obtain a disc
having 125 mm in diameter and 5 mm in thickness. Targets 25 to 34
according to the present invention, and comparative targets 3 and 4
were prepared and the composition is shown in Table 11.
11 TABLE 11 Composition (atom %) Target Ge Sb Dy Te The 25 22.18
22.18 0.15 Balance present 26 22.16 22.16 0.20 Balance invention 27
22.09 22.09 0.50 Balance 28 21.98 21.98 1.00 Balance 29 21.87 21.87
1.50 Balance 30 21.76 21.76 2.00 Balance 31 21.53 21.53 3.00
Balance 32 21.09 21.09 5.00 Balance 33 20.65 20.65 7.00 Balance 34
19.98 19.98 10.00 Balance Comparative 3 22.19 22.19 0.05* Balance 4
19.54 19.54 12.00* Balance *mark means that the value deviates from
the conditions of the present invention.
[0080] Next, each of targets 25 to 34 according to the present
invention, and comparative targets 3 and 4, was bonded to na
backing plate for cooling made of copper with an indium bonding
material of the purity of 99.999 weight %, which was loaded into a
direct current magnetron sputtering apparatus, and the distance
between a target and a substrate (an Si wafer formed with SiO.sub.2
having 100 nm in thickness on the surface thereof) was set to be 70
nm. After vacuumizing was performed to reach an ultimate pressure
of less than or equal to 5.times.10.sup.-5 Pa, an Ar gas was
supplied to be a total pressure of 1.0 Pa. Under the conditions
of
[0081] Substrate temperature: room temperature,
[0082] Power input: 50 W (0.4 W/cm.sup.2),
[0083] sputtering was carried out to obtain phase change recording
films 25 to 34 according to the present invention, and phase change
recording films 3 and 4 having the same thickness of 300 nm on the
surface of the substrate.
[0084] The composition of the phase change recording films 25 to 34
according to the present invention, and comparative phase change
recording films 3 and 4, which are obtained in this way, were
measured by ICP (inductively coupled plasma method), and the
results are shown in Table 12. In addition, after the phase change
recording films 25 to 34 according to the present invention, and
the comparative phase change recording films 3 and 4, were kept for
crystallization at a temperature of 300.degree. C. for 5 minutes in
vacuum, the specific resistances thereof were measured by the four
point probe method. In addition, under the same conditions as
described above, a film was formed on the polycarbonate substrate
having 120 mm in diameter and 3 .mu.m in thickness. The coated film
was completely peeled off and powdered, and the crystallization
temperature was measured by DTA (Differential Thermal Analysis
Method) under the conditions which temperature rose to at a rate of
10.degree. C./min and argon gas was supplied at a rate of 200
ml/min. The results of the measurement are shown in Table 12. In
addition, the amounts of the samples used for this measurement were
all the same 15 mg. Here, the exothermic peak appearing in the
vicinity of 150 to 300.degree. C. is regarded as the
crystallization temperature.
12 TABLE 12 Specific Crystallization Phase change Composition (atom
%) Resistance temperature recording film Ge Sb Dy Te (.OMEGA.
.multidot. cm) (.degree. C.) The 25 22.71 23.25 0.14 Balance 5.40
.times. 10.sup.-2 159.4 present 26 22.85 23.17 0.18 Balance 6.04
.times. 10.sup.-2 160.6 invention 27 22.58 22.92 0.48 Balance 7.12
.times. 10.sup.-2 164.1 28 22.36 22.79 0.96 Balance 8.90 .times.
10.sup.-2 170.1 29 22.20 22.54 1.44 Balance 9.97 .times. 10.sup.-2
176.0 30 21.99 22.18 1.90 Balance 1.28 .times. 10.sup.-1 181.9 31
21.85 21.97 2.89 Balance 8.57 .times. 10.sup.-1 193.8 32 21.46
21.66 4.93 Balance 7.59 .times. 10.degree. 217.6 33 20.94 21.23
6.95 Balance 2.71 .times. 10.sup.1 241.3 34 20.41 20.72 9.92
Balance 4.85 .times. 10.sup.1 276.9 Comparative 3 22.50 22.74 0.03*
Balance 3.78 .times. 10.sup.-2 158.9 4 19.87 20.05 11.91* Balance
7.72 .times. 10.sup.1 326.2 *mark means that the value deviates
from the conditions of the present invention.
[0085] From the result shown in Tables 9 and 10 in Example 5 and as
shown in Tables 11 and 12 in Example 6, it can be understood that
the crystallized phase change recording films 15 to 34 according to
the present invention which are obtained by sputtering using the
targets 15 to 34 according to the present invention including 1 to
10% of Tb or Dy have a higher specific resistance compared with the
comparative crystallized phase change recording films 1 or 3 which
are obtained by sputtering using the comparative targets 1 or 3
including less than 1% of Tb or Dy, and in addition, it is not
preferable because the crystallization temperature of the
comparative crystallized phase change recording films 2 or 4 which
are obtained by sputtering using the comparative targets 2 or 4
including more than 10% of Tb or Dy, increase too much. Therefore,
it can be understood that the content of Tb or Dy is preferably in
the range of 1 to 10%.
[0086] In addition, the same result is also obtained in case that
the film includes a total of 0.1 and 10% of at least one or two
elements selected from the group consisting essentially of Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu aside from Tb and
Dy.
[0087] As described above, according to the present invention, an
appropriately high resistance value can be obtained and a current
value at the time of writing and erasing operation can be reduced,
which contribute to low power consumption and to micro-fabrication.
Further, characteristic of a phase change type non-volatile memory
film can be improved and the manufacturing cost can be reduced.
With all the merits described above, the present invention may
contribute very much to the development of new semiconductor memory
industry.
[0088] The foregoing is considered as illustrative only of the
principles of the invention. Further, since numerous modifications
and changes will readily occur to those skilled in the art, it is
not desired to limit the invention to the exact construction and
operation shown and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention.
* * * * *