JP2002309366A - Target material for sputtering and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a (Zrx , Hf1-x )Siy O2(1+y) target material for sputtering and depositing an oxide thin film which has a high dielectric constant and a small leak current, is usable as a high dielectric gate insulation film provided with characteristics replaceable to an SiO2 film, and is suitable for the deposition of a (Zrx , Hf1-x )Siy O2(1+y) film, and a production method therefor. SOLUTION: The target material for sputtering is expressed by the composition of (Zrx , Hf1-x )Siy O2(1+y) (0<=x<=1, and 0.5<=y<=1.2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an oxide thin film having a large dielectric constant and a small leak current (Zr _x ,
The present invention relates to a sputtering target represented by a composition of Hf _1-x ) Si _y O _{2 (1 + y)} (0 ≦ x ≦ 1, 0.5 ≦ y ≦ 1.2) and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an SiO ₂ film has been used as a gate insulating film of a MOS transistor. However, as the gate length becomes shorter, the gate insulating film needs to be made thinner. However, when the thickness of the gate insulating film is 4 nm or less, a tunnel current which cannot be avoided physically flows, and a problem arises that the transistor does not operate. Therefore,
While still thin SiO ₂ equivalent thickness by using a high dielectric constant material for the gate insulating film, considered to increase the physical film thickness have been ongoing, and ZrO _2, HfO ₂ film or SiO ₂ The ZrO ₂ and HfO ₂ films to be contained are attracting attention. As a method of forming these thin films, a method of performing reactive sputtering using a metal Zr, Hf or Zr, Hf silicide target has been used. However, in the case of reactive sputtering, since oxygen is contained in the gas, an SiO ₂ film having a low dielectric constant is formed at the interface between the gate insulating film and the Si substrate, and there is a problem that the overall dielectric constant is reduced. Therefore, a method of forming a film by rf sputtering using a silicon oxide target of Zr or Hf has recently been proposed.

As a characteristic generally required for a sputtering target, a high-density target is required in order to prevent a decrease in yield due to generation of particles on a film formation surface. In the case of a gate insulating film, a film having a high purity is required because it is formed directly on a Si substrate. But Z
In the case of r and Hf silicates, ZrO ₂ , HfO ₂ and SiO
The oxide mixing method using a ₂ Zr, it is difficult to obtain a silicon oxide single Hf, burning is carried out ZrO _2, mixed phase of HfO ₂ and SiO _2, a large volume of ZrO _2, HfO ₂ There is a problem that a large number of cracks are generated due to a phase transformation accompanied by a change. Further, commercially available ZrO ₂ and HfO ₂ powders have a purity of only about 2N, and cannot obtain the purity required for a gate insulating film target.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention can be used as a high-dielectric gate insulating film having characteristics replacing the SiO ₂ film.
r _x , Hf _1-x ) Si _y O _{2 (1 + y)} for sputtering to form an oxide thin film having a large dielectric constant and a small leak current (Zr _x , Hf _{1- x) x} ) It is an object to provide a Si _y O _{2 (1 + y)} target and a method for manufacturing the same.

[0005]

SUMMARY OF THE INVENTION (Zr _x , Hf _{1 -x} ) Si synthesized by a wet method using zirconium chloride or hafnium chloride or zirconium oxychloride or hafnium oxychloride and a silicon-containing alkoxide as starting materials.
_y O _{2 (1 + y)} composition powder, temperature 1200 ° C or more, pressure 200 kg / cm ²
By firing under pressure as described above, a target having the following characteristics can be obtained. That is, the present invention obtains the following targets. 1. A sputtering target represented by a composition of (Zr _x , Hf _1-x ) Si _y O _{2 (1 + y)} (0 ≦ x ≦ 1, 0.5 ≦ y ≦ 1.2). 2. The above (1), wherein the relative density is 95% or more.
The target for sputtering according to the above. 3. Na, K, Ca, Fe, Ni, Co, C contained in the target
The total amount of r, Cu and Al is 100ppm or less, and each radioactive element of U and Th
3. The sputtering target according to 1 or 2, wherein the sputtering target is 10 ppb or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As starting materials, chlorinated purified zirconium oxychloride or hafnium oxychloride having a purity of 3N or more, preferably 4N or more, and Si-containing alkoxides having a purity of 5N or more are weighed to obtain a target composition.・ Mix. After adding an equivalent amount or more of ultrapure water to the mixed aqueous solution to hydrolyze, the mixture is filtered and dried. 600 ° obtained crystalline hydrated zirconium silicate or hafnium powder
(Zr _x , Hf _1-x )
Mixture of (Zr _X , Hf _1-X ) SiO ₄ , ZrO ₂ , HfO ₂ , SiO ₂ which can be represented by the composition Si _y O _{2 (1 + y)} (0 ≦ x ≦ 1, 0.5 ≦ y ≦ 1.2) A powder can be obtained. Here, if y <0.5, the volume fraction of ZrO ₂ and HfO ₂ having a large volume change due to phase transformation during firing increases, and cracks occur in the sintered body. When y> 1.2, free SiO ₂ is (Zr _X , Hf _1-X )
Since the sintering of the SiO ₄ particles is inhibited, a sintered body having a relative density of 95% or more cannot be obtained. Therefore, in the zirconium silicate or hafnium represented by the above chemical formula, the Si content is preferably 0.5 ≦ y ≦ 1.2.

(Zr) obtained by the above synthesis method_x, Hf_1-x) Si_yO
_{2 (1 + y)}Fill the powder into a graphite die,
00 ° C or more, pressure 200kg / cm^TwoHot press
With this, the firing without cracks and cracks with a relative density of 95% or more
You can get union. Hot press temperature is 1200 ° C
In the following, sintering is insufficient and the required density can be obtained
Can not. When hot pressing at 1600 ° C or more,
(Zr_X, Hf_1-X) SiO_FourDecomposition and SiO _TwoReduction and evaporation
This causes cracks and pores to remain in the sintered body. On the other hand,
Higher press pressure contributes to higher density,
Considering the strength of steel, it is practically 300kg / cm^TwoThe following is preferred
200kg / cm^TwoBelow, sufficient density cannot be obtained.

[0008]

Next, an embodiment will be described. Note that the present embodiment is for showing an example of the present invention, and the present invention is not limited to these embodiments. That is, it includes other aspects and modifications included in the technical idea of the present invention.

(Example 1) A zirconium oxychloride ZrOCl ₂ aqueous solution having a purity of 3N or more and tetraethoxysilane Si (OC ₂ H ₅ ) _{4 having} a purity of 5N or more were used as starting materials (Zr _x , Hf _1-x ) Si _y O
_{2 In the} composition represented by the formula _{(1 + y)} , X = 1, y = 0.5, 0.
A predetermined amount was mixed so as to be 7, 1.0, 1.2. Further, 1.5 times equivalent of an aqueous solution of ZrOCl ₂ used (NH ₄ ) OH and ultrapure water of 3 equivalents of tetraethoxysilane were added, and the mixture was heated to 80 ° C. After stirring for 100 hours while heating, the mixture was cooled and filtered. Dry the obtained crystalline hydrated zirconium silicate powder, 850 °
Perform a synthetic heat treatment in the atmosphere of C × 10h, X = 1, y = 0.5, 0.
(Zr _x , Hf _1-x ) Si _y O _{2 (1 + y )} powders of 7, 1.0 and 1.2 were obtained.
This powder was pulverized and classified with a 100 mesh sieve. As shown in Table 1, the chemical analysis values of the obtained powder were Na, K, Ca, Fe, N
The total amount of i, Co, Cr, Cu, and Al satisfied 100 ppm or less, and the radioactive elements of U and Th satisfied 10 ppb or less.

[0010]

[Table 1]

[0011] Also. As a result of XRD measurement of each powder, y =
The 0.5 and 0.7 composition powder had a two-phase mixed phase of ZrSiO ₄ and ZrO ₂ , the y = 1 composition powder had a ZrSiO ₄ single phase, and the y = 1.2 composition had an amorphous phase of ZrSiO ₄ and SiO ₂ . These powders were filled in a graphite die and baked at 200 kg / cm ² × 2 h in an Ar gas atmosphere at 1200 ° C. and 1500 ° C., respectively. Table 2 shows the density of the obtained sintered body and the result of the crystal phase determined by XRD measurement. The crystal phase of the sintered body is a mixed phase of ZrSiO ₄ and monoclinic ZrO ₂ with y = 0.5, 0.7 composition, ZrSiO ₄ single phase with y = 1 composition, and ZrSi with y = 1.2 composition.
It was a mixed phase of O ₄ and SiO ₂ (cristobalite). Based on this XRD measurement result, the density of each composition was calculated from the composite rule and the relative density of the sintered body was obtained. Thus, the characteristics as a sputtering target could be satisfied.

[0012]

[Table 2]

(Example 2) Hafnium oxychloride HfOCl ₂ having a purity of 3N or more was used as a starting material, and the composition was set to X = 0.
Powder production and firing were performed under the same conditions as in Example 1 except that the temperature was changed to 900 ° C. As in Example 1, the chemical analysis value of the powder is shown in Table 1, and the XRD result and the relative density of the sintered body are shown in Table 2. All of the obtained sintered bodies were free from cracks and cracks, had a relative density of 95% or more, and could satisfy the characteristics as a sputtering target.

Example 3 A powder was prepared and fired under the same conditions as in Example 2 except that the composition was changed to x = 0.5. The chemical analysis values of the powders are shown in Table 1 as in Example 1, and the XR
The results and relative density are shown in Table 2. No cracks or cracks occurred in any of the obtained sintered bodies, and the relative density was 95%.
% Or more, so that the characteristics as a sputtering target could be satisfied.

Comparative Example 1 A powder was produced and fired under the same conditions as in Example 3 except that X = 0.5, y = 0.4 and 1.3. XRD result and relative density of the obtained sintered body,
Table 2 shows the presence or absence of cracks in the same manner as described above. Y = 0.4
The sintered body of the composition has a relative density of 9 by hot pressing at 1500 ° C.
Although it was 5% or more, generation of many cracks was observed in the sintered body. Further, the sintered body having the composition of y = 1.3 had a relative density of 95% or less even in a hot press at 1500 ° C. As described above, the sintered body shown in Comparative Example 1 does not satisfy the characteristics as a sputtering target, and may cause a reduction in processing yield and a yield due to generation of particles during film formation.

(Comparative Example 2) In the composition of X = 0.5, y = 1.0,
Powder production and firing were performed under the same conditions as in Example 1 except that the temperature during hot pressing was 1150 ° C and 1600 ° C. Table 2 shows the XRD results, the relative density, and the presence or absence of cracks and cracks of the obtained sintered body in the same manner as described above. The relative density of the sintered body hot-pressed at 1150 ° C. was 93%. The relative density of the sintered body hot-pressed at 1600 ° C is 92
%, A large number of fine cracks are present, and neither sintered body can satisfy the characteristics as a sputtering target, and may cause a reduction in processing yield or yield due to generation of particles during film formation.

[0017]

According to the present invention, SiO_TwoWith characteristics that can replace membrane
Can be used as a high dielectric gate insulating film
(Zr_x, Hf_1-x) Si_yO_{2 (1 + y)}Dielectric constant suitable for film formation
For forming large oxide thin films with small leakage current
For sputtering (Zr_x, Hf_1-x) Si _yO_{2 (1 + y)}Target
It has an excellent effect that it can be obtained. Also,
The sintered compact target has high density and high purity,
It has a remarkable feature that there is no occurrence of cracks or cracks.

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Claims (5)

[Claims] (1) (Zr _x , Hf _1-x ) Si _y O _{2 (1 + y)} (0 ≦ x ≦ 1, 0.5
≦ y ≦ 1.2) a sputtering target represented by the composition: 2. The sputtering target according to claim 1, wherein the relative density is 95% or more. 3. Na, K, Ca, F contained in the target
3. The sputtering target according to claim 1, wherein the total amount of e, Ni, Co, Cr, Cu, and Al is 100 ppm or less, and each of the radioactive elements U and Th is 10 ppb or less. 4. The method for producing a sputtering target according to claim 1, wherein zirconium chloride, hafnium chloride, zirconium oxychloride, hafnium oxychloride and silicon-containing alkoxide are used as starting materials. 5. A powder synthesized from starting materials of zirconium chloride or hafnium chloride or zirconium oxychloride or hafnium oxychloride and a silicon-containing alkoxide at a temperature of 1200 ° C. to 1600 ° C. and a pressure of 200 kg / cm.
^The method for producing a sputtering target according to any one of claims 1 to 3, wherein pressure firing is performed at ^two or more times.