Metal treatment – Stock – Titanium – zirconium – or hafnium base
Reexamination Certificate
2001-12-05
2004-04-20
Oltmans, Andrew L. (Department: 1742)
Metal treatment
Stock
Titanium, zirconium, or hafnium base
C148S668000, C148SDIG001, C420S422000, C420S578000
Reexamination Certificate
active
06723183
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a non-brittle silicide target suitable for forming a ZrO
2
.SiO
2
or HfO
2
.SiO
2
film that can be used as a high dielectric gate insulating film.
BACKGROUND OF THE INVENTION
The thickness of a dielectric gate insulating film affects the performance of an MOS transistor significantly, and should be such that the boundary to the silicon substrate is electrically smooth, and the mobility of carriers does not deteriorate.
Heretofore, an SiO
2
film has been used as the gate insulating film, and this has been most excellent in boundary characteristics. An SiO
2
film has characteristics such that the thinner the SiO
2
film used as the gate insulating film is, the larger the number of carriers, i.e. electrons or holes is, thereby increasing the drain current.
For these reasons, the SiO
2
film has been thinned to lower current and voltage values within the extent not to cause dielectric breakdown. However, there is limitation in thinning such SiO
2
films, and when the thickness of the SiO
2
film is decreased to 2 to 3 nm or less, a tunnel current flows and the SiO
2
film cannot function as an insulating film.
On the other hand, although transistors have been downsized, this is meaningless as long as there is limitation in the thickness of the SiO
2
film that functions as a gate insulating film as described above, and the performance of transistors has not been improved.
Also, in order to lower the power voltage of an LSI to save power consumption, the gate insulating film must further be thinned. However, since there is a problem of the dielectric breakdown of the gate when the thickness of the SiO
2
film is 3 nm or less, decrease in film thickness itself has limitation.
For the above-described reasons, high dielectric gate insulating films are recently studied for substituting the SiO
2
film. The high dielectric gate insulating films of interest include a ZrO
2
.SiO
2
film or HfO
2
.SiO
2
film.
These high dielectric gate insulating films are characterized in that the capacity equivalent to the capacity of an SiO
2
film can be attained by a relatively thick film, and tunnel leakage current can be inhibited. Also, since these gate-insulating films can be considered to be SiO
2
films to which Zr or Hf is added, their interfacial characteristics can be expected to be similar to those of SiO
2
.
Consequently, there is a need for a sputtering target that can produce a high-quality ZrO
2
.SiO
2
or HfO
2
.SiO
2
high dielectric gate insulating film easily and reliably.
OBJECT OF THE INVENTION
In order to solve the above-described problems, the object of the present invention is to provide a non-brittle silicide target suitable for forming a ZrO
2
.SiO
2
or HfO
2
.SiO
2
film that can be used as a high dielectric gate insulating film that has properties to substitute an SiO
2
film, and a method for manufacturing such a silicide target
SUMMARY OF THE INVENTION
According to a first embodiment of the present invention, there is provided a non-brittle silicide target for forming a gate oxide film made of MSi
0.8-1.2
(M: Zr, Hf).
According to a second embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to the first embodiment, wherein no free Si is present.
According to a third embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to the first or second embodiments, made of the single phase of MSi.
According to a fourth embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to the first or second embodiments, made of a mixed phase of at least two selected from MSi, M
5
Si
4
, and MSi
2
.
According to a fifth embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to any of the first to fourth embodiments, wherein the relative density is 99% or more.
According to a sixth embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to any of the first to fifth embodiments, wherein the average crystal grain diameter is 30 &mgr;m or less.
According to a seventh embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to any of the first to fifth embodiments, wherein the average crystal grain diameter is 10 &mgr;m or less.
According to an eighth embodiment of the present invention, there is provided the non-brittle silicide target for forming a gate oxide film according to any of the first to seventh embodiments, wherein the transverse rupture strength thereof is 200 MPa or more.
According to a ninth embodiment of the present invention, there is provided a method for manufacturing a non-brittle silicide target for forming a gate oxide film consisting of MSi
0.8-1.2
(M: Zr, Hf), comprising the steps of mixing hydrogenated metal (M) powder and Si powder in a mole ratio of 1:0.8 to 1:1.2, and baking and sintering the mixture.
According to a tenth embodiment of the present invention, there is provided the method for manufacturing a non-brittle silicide target for forming a gate oxide film according to ninth embodiment, wherein dehydrogenation and silicide synthesis are carried out by heating during baking.
According to an eleventh embodiment of the present invention, there is provided the method for manufacturing a non-brittle silicide target for forming a gate oxide film according to the tenth embodiment, wherein baking is performed at a temperature between 600° C. and 800° C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A ZrO
2
.SiO
2
film or HfO
2
.SiO
2
film that can be used as a high dielectric gate insulating film having properties to substitute an SiO
2
film can be formed by oxygen reactive sputtering using a ZrSi or HfSi target.
The present invention provides a silicide target made of MSi
0.8-1.2
(M: Zr, Hf), a silicide target made of the single phase of MSi that contains no free Si, or a silicide target made of a mixed phase of at least two selected from MSi, M
5
Si
4
, and MSi
2
.
The M/Si mole ratio required for a high dielectric gate insulating film is 1:1. To go so far, when a high dielectric gate insulating film is produced in a prescribed mole ratio, it can be produced from a mixed phase of a composition extremely deviated from the desired mole ratio, such as metal powder and Si powder or MSi
2
powder.
However, it has been known that a free Si phase takes significant part in the occurrence of metal silicide particles. In other words, it has been considered that when a sputtering target of a structure having a mixed phase of silicide and Si is sputtered, the irregularity of the surface caused by difference in sputtering rates between the Si phase and the metal silicide phase becomes prominent, resulting in increase in the number of particles.
According to the present invention, since free Si is eliminated, and the components are limited to three phases of MSi, M
5
Si
4
, or MSi
2
close to the desired mole ratio, the irregularity of the eroded surface caused by difference in sputtering rates can be minimized, and the occurrence of particles can be prevented.
The above-described silicide target for forming gate oxide films has a disadvantage of high brittleness. According to the present invention, the relative density is 99% or more, and the average crystal grain particle diameter is 30 &mgr;m or less, preferably 10 &mgr;m or less. Thereby, a non-brittle silicide target for forming gate oxide films with a transverse rupture strength of 200 or more MPa can be obtained.
If the relative density is less than 99%, and the average crystal grain particle diameter exceeds 30 &mgr;m, brittleness is lowered due to the shortage of density, resulting in poor machinability. Furthermore, increase in the number of particles is caused due to the breakdown and scattering of brittle crystals. Therefore the
Miyashita Hirohito
Oda Kunihiro
Howson and Howson
Nikko Materials Company Limited
Oltmans Andrew L.
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