JP2007297715A - Manufacturing method of silicide target for depositing gate oxide film with excellent embrittlement resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a silicide target with excellent embrittlement resistance which is suitable for depositing a silicide target for depositing a ZrO<SB>2</SB>SiO<SB>2</SB>film or a HfO<SB>2</SB>SiO<SB>2</SB>film that can be used as a high dielectric gate insulating film having properties to substitute an SiO<SB>2</SB>film. <P>SOLUTION: A hydrogenated metal (M) powder and a Si powder are prepared/mixed in the mole ratio of 1:0.8 to 1:1.2, baked to simultaneously perform dehydogenation and silicide formation by the heating during the baking. The obtained silicide powder is crushed and baked to manufacture a sintered body consisting of MSi<SB>0.8-1.2</SB>(M:Zr, Hf) with the relative density of ≥99% without any free Si present. The silicide target for forming a gate oxide film with excellent embrittlement resistance can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for manufacturing a silicide target having a high embrittlement resistance 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.

The film thickness of the dielectric gate insulating film greatly affects the performance of the MOS transistor, and it is necessary that the interface with the silicon substrate is electrically smooth and the carrier mobility does not deteriorate.
Conventionally, a SiO ₂ film has been used as the gate insulating film, but it was the most excellent in terms of interface characteristics. The thinner the SiO ₂ film used as the gate insulating film, the greater the number of electrons or holes that are carriers, so that the drain current can be increased.

For this reason, the SiO ₂ film has been made finer to reduce the current voltage value, and the film thickness has been reduced within a range where dielectric breakdown does not occur. However, there is a limit to the reduction in the thickness of the SiO ₂ film. When the SiO ₂ film has a thickness of ₂ to 3 nm or less, a tunnel leak current flows and the insulating film is not operated.
On the other hand, we are trying to make transistors finer, but as mentioned above, there is a limit to the thickness of the SiO ₂ film, which is a gate insulating film, so that miniaturization of transistors does not make sense and performance is not improved. Produced.
Further, in order to lower the power supply voltage of LSI and lower the power consumption, it is necessary to make the gate insulating film thinner. However, if the SiO ₂ film is 3 nm or less, there is a problem of gate dielectric breakdown as described above. There was a limit to thinning itself.

From the above, recently, a high dielectric gate insulating film has been studied in place of the SiO ₂ film. The ZrO ₂ · SiO ₂ or HfO ₂ · SiO ₂ film is attracting attention as the high dielectric gate insulating film.
This high dielectric gate insulating film is a relatively thick film, and can obtain a capacitance equivalent to that of the SiO ₂ film, and can suppress a tunnel leakage current. Moreover, since it can be assumed that the addition of Zr or Hf to SiO _2, the interface characteristics are also expected to be close to SiO _2.
Therefore, a sputtering target capable of easily and stably forming a high-quality ZrO ₂ · SiO ₂ or HfO ₂ · SiO ₂ high dielectric gate insulating film is desired.

The present invention, in order to solve the above problems, formation of _ZrO 2 · SiO ₂ or _HfO 2 · SiO ₂ film can be used as a high dielectric gate insulating film having a characteristic alternative to the SiO ₂ film It is an object of the present invention to provide a method for manufacturing a silicide target having a high brittleness resistance.

The present invention is characterized in that 1) a silicide target for gate oxide film formation having excellent embrittlement resistance composed of MSi _0.8-1.2 (M: Zr, Hf), and 2) free Si does not exist. The silicide target for forming a gate oxide film having excellent embrittlement resistance as described in 1 above, and 3) the gate oxide film formation having excellent embrittlement resistance as described in 1) or 2) above, comprising a single phase of MSi. 4) The formation of a gate oxide film having excellent embrittlement resistance according to 1) or 2) above, comprising at least two mixed phases selected from 4) MSi, M ₅ Si ₄ or MSi ₂ 5) Silicide target for forming a gate oxide film excellent in embrittlement resistance according to any one of 1) to 4) above, wherein 6) an average crystal Particle size The silicide target for forming a gate oxide film having excellent embrittlement resistance according to any one of 1) to 5) above, wherein the average crystal grain size is 10 μm or less. The silicide target for forming a gate oxide film having excellent embrittlement resistance as described in any one of 1) to 5) above, and 8) The bending strength is 200 MPa or more. An object of the present invention is to produce a silicide target for forming a gate oxide film excellent in embrittlement resistance as described in any of the above.
As a specific method,
1. Preparation and mixing of metal hydride (M) powder and Si powder in a molar ratio of 1: 0.8 to 1: 1.2, followed by firing and dehydrogenation and silicidation at once by heating during firing The resulting silicide powder is pulverized, sintered, and free of Si, and has a relative density of 99% or more of MSi _0.8-1.2 (M: Zr, Hf). 2. A method for producing a silicide target for forming a gate oxide film excellent in embrittlement resistance characterized by producing a sintered body 2. Firing at 600 ° C. to 800 ° C. A method for manufacturing a silicide target for forming a gate oxide film, which is excellent in embrittlement.

The target obtained by the manufacturing method of the present invention can be used as a high dielectric gate insulating film having characteristics replacing the SiO ₂ film to form a ZrO ₂ · SiO ₂ or HfO ₂ · SiO ₂ film. It is a suitable silicide target made of MSi _0.8-1.2 (M: Zr, Hf) rich in embrittlement resistance. The silicide target obtained by this method can suppress the growth of crystal grains, can achieve high density when molding, and the silicide target with high relative density of 99% or more has an excellent bending strength of 200 MPa or more. Have high strength. Furthermore, the silicide target having such a high density has a remarkable effect of preventing generation of particles due to pores and generation of particles due to breakage and scattering of brittle structures during sputtering.

_ZrO 2 · SiO ₂ or _HfO 2 · SiO ₂ film can be used as a high dielectric gate insulating film having a characteristic alternative to the SiO ₂ film, the oxygen reactive sputtering using a target of ZrSi or HfSi Can be formed.
The present _{invention, MSi} 0.8-1.2: a silicide target made of (M Zr, Hf), there is no free Si, silicide target made of MSi single phase or _MSi, M 5 Si ₄ or MSi ₂ is a silicide target composed of at least two mixed phases selected from 2.
The molar ratio required for the high dielectric gate insulating film is Zr: Si = 1: 1. When preparing to a predetermined molar ratio, it can be said that it is possible to produce even a mixed phase having a composition greatly deviating from a desired molar ratio, such as Zr metal powder and Si powder or ZrSi ₂ powder.
However, it is known that the free Si phase is greatly involved in the generation of metal silicide particles. That is, when a sputtering target having a structure in which a silicide phase and a Si phase are mixed is sputtered, surface unevenness due to a difference in sputtering speed between the Si phase and the metal silicide phase becomes prominent, and this step causes an increase in particles. It is considered.
In the present invention, free Si is eliminated, and it is limited to three phases of MSi, M ₅ Si ₄ or MSi _{2 in} the vicinity of a desired molar ratio, thereby reducing unevenness of the erosion surface due to the difference in sputtering rate and generating particles. Can be suppressed.

Although the above-described silicide target for forming a gate oxide film has a drawback of high brittleness, in the present invention, the relative density is 99% or more, the average crystal grain size is 30 μm or less, preferably the average crystal grain size is 10 μm or less. As a result, a silicide target for forming a gate oxide film having a bending strength of 200 MPa or more and excellent in embrittlement resistance can be obtained.
If the relative density is less than 99% and the average crystal grain size exceeds 30 μm, the density is insufficient and the brittleness is lowered and the workability is also deteriorated. Furthermore, it causes an increase in particles due to the breaking and scattering of brittle crystals. Therefore, the above range is desirable.

In order to manufacture a silicide target for forming a gate oxide film having excellent embrittlement resistance composed of MSi _0.8-1.2 (M: Zr, Hf), metal hydride (M) powder and Si powder are mixed with 1: After preparing and mixing to a molar ratio of 0.8 to 1: 1.2, firing is performed at 600 ° C to 800 ° C.
Although it is conceivable to use Zr and Hf powders, Zr and Hf powders have a strong oxidizing power and cause a problem of ignition when pulverized.
Therefore, zirconium hydride or hafnium hydride is used to prevent such ignition. These hydrogenated powder and silicon powder are used after being finely pulverized to an average particle size of 10 μm or less. By using this fine powder, it becomes possible to increase the density during sintering.
Dehydrogenation and silicidation are performed by heating during the firing. Dehydrogenation occurs from 600 ° C. Sintering is performed in a vacuum (1 × 10 ⁻⁴ to 1 × 10 ⁻² Torr), but the atmosphere is slightly hydrogen for dehydrogenation.

As described above, when performing heat synthesis, grain growth is suppressed by performing dehydrogenation and silicidation at a low temperature at which grain growth does not occur, and the sintered powder remains fine. The crystal grain size can be 30 μm or less. When the calcined powder becomes coarse, fine pulverization before sintering is difficult, which causes residual coarse grains and a decrease in density.
As described above, the present invention has a great feature that it can suppress the growth of crystal grains because it is fired at a low temperature. And when densifying, densification can be achieved.
A silicide target whose relative density is increased to 99% or more shows a strength with a bending strength of 200 MPa or more.
The silicide target of the present invention having a high density has an effect of preventing generation of particles due to pores and generation of particles due to breakage and scattering of a brittle structure during sputtering.

Next, examples will be described. In addition, a present Example is for showing an example of invention, This invention is not restrict | limited to these Examples. That is, other aspects and modifications included in the technical idea of the present invention are included.
Example 1
ZrH ₂ powder and Si powder were mixed and heated at 800 ° C. in a vacuum to perform a dehydrogenation reaction and a silicide synthesis reaction all at once to obtain a synthetic powder of ZrSi _x (x = 1.0). . The silicide powder was pulverized to obtain a -200 mesh silicide powder. This silicide powder was confirmed by XRD to consist only of ZrSi _1.0 phase.
Using this silicide powder, a sintered body having a density of 99.2% was produced by hot pressing, and a target of φ300 mm × 6.35 mmt was produced by machining. The crystal grain size of the sintered compact target was 15 μm.
Sputtering was performed using the target thus prepared, and the particles on the 6-inch wafer were measured. As a result, a total of 25 particles having a size of 0.2 μm or more were observed.
Furthermore, when the erosion surface of the target was observed, no trace of ZrSi _x phase destruction was observed, and no surface irregularities due to the difference in sputtering rate were observed. Moreover, it was 220 MPa as a result of measuring the bending strength of a target.

(Example 2)
ZrH ₂ powder and Si powder were mixed and heated at 800 ° C. in a vacuum to perform dehydrogenation reaction and silicide synthesis reaction all at once to obtain a synthetic powder of ZrSi _x (x = 0.9). . The silicide powder was pulverized to obtain a -200 mesh silicide powder. This silicide powder was confirmed by XRD to consist of two phases, a Zr ₅ Si ₄ phase and a ZrSi phase.
Using this silicide powder, a sintered body with a density of 99.3% was produced by hot pressing, and a target of φ300 mm × 6.35 mmt was produced by machining. The crystal grain size of the sintered compact target was 9 μm.
Sputtering was performed using the target thus prepared, and the particles on the 6-inch wafer were measured. As a result, a total of 35 particles having a size of 0.2 μm or more were obtained.
Furthermore, when the erosion surface of the target was observed, no trace of ZrSi _x phase destruction was observed, and no surface irregularities due to the difference in sputtering rate were observed. Moreover, it was 215 MPa as a result of measuring the bending strength of a target.

(Example 3)
ZrH ₂ powder and Si powder are mixed and heated at 800 ° C. in a vacuum to perform dehydrogenation reaction and silicide synthesis reaction all at once, ZrSi _x (x = 0.8 and x = 1.2) Two types of synthetic powders were obtained. The silicide powder was pulverized to -200 mesh, and then a silicide powder mixed so that the molar ratio Si / Zr = 1.0 was obtained. It was confirmed by XRD that this silicide powder was composed of three phases of Zr ₅ Si ₄ phase, ZrSi phase and ZrSi ₂ phase.
Using this silicide powder, a sintered body having a density of 99.0% was produced by hot pressing, and a target of φ300 mm × 6.35 mmt was produced by machining. The crystal grain size of the sintered compact target was 25 μm.
Sputtering was performed using the target thus prepared, and the particles on the 6-inch wafer were measured. As a result, a total of 30 particles having a size of 0.2 μm or more were obtained.
Further, when the erosion surface of the target was observed, no trace of ZrSi _x phase destruction was observed, and almost no surface unevenness due to the difference in sputtering rate was observed. Moreover, it was 205 MPa as a result of measuring the bending strength of a target.

(Comparative Example 1)
ZrH ₂ powder and Si powder were mixed and heated at 1200 ° C. in a vacuum to perform a dehydrogenation reaction and a silicide synthesis reaction all at once to obtain a synthetic powder of ZrSi _x (x = 1.0). . This silicide powder was pulverized to obtain a silicide powder having a -200 mesh. This silicide powder was confirmed by XRD to consist only of the ZrSi phase.
Using this silicide powder, a sintered body having a density of 89.0% was produced by hot pressing, and a target of φ300 mm × 6.35 mmt was produced by machining. The crystal grain size of the sintered compact target was 100 μm.
Sputtering was performed using the target thus prepared, and the particles on the 6-inch wafer were measured. As a result, a total of 95 particles having a size of 0.2 μm or more were observed.
Furthermore, when the erosion surface of the target was observed, the ZrSi _x phase was destroyed, and traces that seemed to have clearly become dust generation sources were observed. Although the surface unevenness due to the difference in the sputtering rate was not seen, many nodules were generated. Moreover, it was 150 MPa as a result of measuring the bending strength of a target.

(Comparative Example 2)
ZrH ₂ powder and Si powder are mixed and heated at 1200 ° C. in a vacuum to perform dehydrogenation reaction and silicide synthesis reaction all at once, and ZrSi _x (x = 0.6 and 2.2) 2 A kind of synthetic powder was obtained. The silicide powder was pulverized to -200 mesh, and then a silicide powder mixed so that the molar ratio Si / Zr = 1.0 was obtained. It was confirmed by XRD that this silicide powder was composed of _three phases of Zr ₅ Si ₃ phase, ZrSi ₂ phase and Si phase.
Using this silicide powder, a sintered body having a density of 93% was produced by hot pressing, and a target of φ300 mm × 6.35 mmt was produced by machining. The crystal grain size of the sintered compact target was 100 μm.
Sputtering was performed using the target thus prepared, and particles on a 6-inch wafer were measured. As a result, a total of 120 particles having a size of 0.2 μm or more were observed.
Furthermore, when the erosion surface of the target was observed, the ZrSi _x phase was destroyed, and traces that seemed to have clearly become dust generation sources were observed. The surface unevenness | corrugation resulting from a sputtering rate difference was seen, and many nodules were generated. Moreover, it was 165 MPa as a result of measuring the bending strength of a target.

The results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1 above.
As is clear from Table 1, the average crystal grain sizes of the targets of Examples 1 to 3 are all 30 μm or less, and the relative density is 99% or more. The number of particles was 35 or less, no traces of destruction of the ZrSi _x phase were observed, and almost no surface irregularities due to the difference in sputtering rate were observed. Moreover, the bending strength of the target was 220 MPa, 215 MPa, and 205 MPa, and had high bending strength.
In contrast, in Comparative Example 1, the average crystal grain size was as large as 100 μm and the relative density was as low as 89%. As a result, the number of particles was 95 or less, and traces of destruction of the ZrSi _x phase were observed. Although the surface unevenness due to the difference in the sputtering rate was not observed, nodules were generated, and the bending strength of the target was as low as 150 MPa.
In Comparative Example 2, the average crystal grain size was as large as 100 μm and the relative density was as high as 93%, but free Si was present. As a result, the number of particles was 120 or less, and traces of destruction of the ZrSi _x phase were observed. Further, surface irregularities due to the difference in sputtering rate were also observed, nodules were generated, and the bending strength of the target was as low as 165 MPa, resulting in a bad result.
From the above, it can be seen that the advantages of the embodiments of the present invention are clear and have excellent characteristics.

The production method of the present invention is characterized in that a silicide target made of MSi _0.8-1.2 (M: Zr, Hf) rich in embrittlement resistance can be obtained, and the production method of the present invention. The silicide target obtained by the above method can suppress the growth of crystal grains, and can achieve high density when formed. Further, the silicide target having a relative density of 99% or higher has an excellent strength with a bending strength of 200 MPa or more, and the silicide target of the present invention having a higher density has a higher resistance to particles caused by pores during sputtering. It has a remarkable effect of preventing the generation of particles due to generation and breakage and scattering of brittle structures. From the above, it is useful in a suitable silicide target for forming a _ZrO 2 · SiO ₂ or _HfO 2 · SiO ₂ film that can be used as a high dielectric gate insulating film having a characteristic alternative to the SiO ₂ film.

Claims (2)

Preparation and mixing of metal hydride (M) powder and Si powder in a molar ratio of 1: 0.8 to 1: 1.2, followed by firing and dehydrogenation and silicidation at once by heating during firing The resulting silicide powder is pulverized, sintered, and free of Si, and has a relative density of 99% or more of MSi _0.8-1.2 (M: Zr, Hf). A method for producing a silicide target for forming a gate oxide film having excellent embrittlement resistance, comprising producing a sintered body.   6. The method for producing a silicide target for forming a gate oxide film having excellent embrittlement resistance according to claim 5, wherein the firing is performed at 600 ° C. to 800 ° C.