JPH11200025A - Sputtering target material for forming tantalum silicon nitride thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target material capable of forming a (TaSiy )N2 thin film extremely small in local (positional) dispersion on the coating face of structural components at the time of forming a thin film of tantalum silicon nitride [hereinafter shown by the compositional formula of (TaSiy )N2 , where, by atomic ratio, (y): 0.1 to 0.75 and (z): 0.8 to 2.7 are satisfied] by a reactive sputtering method. SOLUTION: This sputtering target material is composed of a hot press sintered body substantially composed of tuntalum silicide phases and metallic Ta phases in the structure, in which the ratio of the tuntalum silicide phases occupies 33 to 92 area % from the observation with structural photography by an electron probe X-ray microanalyzer, moreover, the theoretical density ratio (relative density) is >=90%, and in the case the total comps. is expressed by TaSix the (x) value satisfies 0.1 to 0.65 by atomic ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tantalum silicon nitride [hereinafter referred to as "reactive sputtering"]
Composition formula: (TaSi _y ) N _z . However, the atomic ratio satisfies y: 0.1 to 0.75 and z: 0.8 to 2.7]. When a thin film is formed, local (positional) variations of the constituent components on the film surface are extremely large. Small (TaSi _y )
The present invention relates to a sputtering target material capable of forming an _Nz thin film (hereinafter, simply referred to as a target material).

[0002]

2. Description of the Related Art Conventionally, a (TaSi _y ) N _z thin film is generally used to prevent a reaction between a Pt electrode and a polycrystalline Si plug in a semiconductor memory device, for example, as shown in a schematic longitudinal sectional view of FIG. It is well known that it is provided as a barrier layer. Further, the (TaSi _y ) N _z thin film is
As shown in the schematic explanatory view of FIG. 3, in a reactive sputtering apparatus, a molten polycrystalline Si target material and a sintered metal Ta target material were used as target materials, and the surfaces of these target materials were reduced in a reduced pressure inert gas atmosphere. Are sputtered to evaporate Ta and Si at a predetermined ratio, and react with nitrogen gas introduced together with Ar in the atmosphere (Ta
It is also known to form Si _y ) N _z by depositing it on the surface of a substrate.

[0003]

On the other hand, in recent years, high integration and large capacity of semiconductor devices have been remarkable, and accordingly, the (TaSi _y ) N _z thin film formed on the substrate surface by vapor deposition has been increasing in area. When the (TaSi _y ) N _z thin film has a large area as described above, a conventional sputtering method using a molten polycrystalline Si target material and a sintered metal Ta target material in parallel as the above-mentioned target material is used. Then, Ta, which is a component of the (TaSi _y ) N _z thin film,
And Si tend to have local variations on the film surface, and this variation is a local variation in the characteristics of the (TaSi _y ) N _z thin film, which is a problem in the manufacture of semiconductor devices.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above viewpoint, the area is particularly increased (TaSi
_y ) N_z Localization of Ta and Si on film surface in thin film
Focusing on target materials and conducting research in order to reduce variations
As a result, tantalum silicide powder was used as the raw material powder.
And metal Ta powder, which are blended in a predetermined ratio and mixed.
After combining, fill in carbon mold, and in vacuum
Or in an inert gas atmosphere, temperature: 1750 to 1950
Hot pressing under the conditions of ° C. and pressure: 10 to 50 MPa
By the fact that tantalum silicide phase and gold
The Ta tantalum silicide phase
Structure photo by electron probe X-ray microanalyzer
Occupies 33 to 92% by area, and the theoretical density ratio
(Relative density) is 90% or more, that is, the ratio of pores
Is 10% by volume or less, and the overall composition is represented by a composition formula: TaSi
_x In the case where x is expressed, the x value satisfies the atomic ratio of 0.1 to 0.65.
The sintered body to be added is manufactured, and this sintered body is
In the ring method (TaSi_y ) N_z When forming a thin film
When used as a target material,
(TaSi_y ) N_z Ta and Si on thin film surface
The local variation of
The research results showed that the size was smaller.

The present invention has been made on the basis of the above research results, and comprises a tantalum silicide phase and a metal Ta phase in structure, and the ratio of the tantalum silicide phase is determined by an electron probe X-ray microanalyzer. accounting for 33 to 92 area% was observed with a structural photograph, further theoretical density ratio (relative density) is 90%, that is, the proportion of pores to 10 vol% or less, the total composition of the composition formula: current in TaSi _x When the x value is 0.1 to
(TaSi _y ) N, which is composed of a hot-pressed sintered body satisfying 0.65 and has very small local (positional) variation on the film surface of the constituent components Ta and Si.
_z It is characterized by a target material capable of forming a thin film.

[0006] Next, in the hot-pressed sintered body constituting the target material of the present invention, the composition formula: T, which indicates the ratio of the tantalum silicide phase, the theoretical density ratio, and the overall composition
The x value of the aSi _x explaining reasons for limiting as described above. (A) Tantalum silicide phase ratio When the ratio is less than 33 area%, (TaSi _y ) N
_{z The} tendency to decrease the effect of suppressing the local variation of the constituent components in the thin film becomes apparent. On the other hand, if the ratio exceeds 92 area%, the film formation rate suddenly decreases. 92 area%, desirably 50 to
80% by area.

(B) Theoretical Density Ratio When the theoretical density ratio is less than 90%, the ratio of pores relatively increases, which not only causes particles during sputtering but also causes pore components to intervene in the thin film. As a result, the characteristic of the thin film becomes significantly impaired, so that the theoretical density ratio is set to 90% or more, preferably 95% or more.

[0008] (c) a composition formula: x value x value of TaSi _x is the street thin film of the above composition formula: (TaSi _y) N _z
Are changed in accordance with the y value and the z value in the above, that is, the y value and the z value determined to have the characteristics required by the thin film, and thus the values are set to 0.1.
The y value and the z value of the thin film are less than the above-mentioned predetermined values, that is, y: 0.1 to 0.7.
5, z: out of the range of 0.8 to 2.7, and the desired characteristics cannot be ensured in the thin film.
x value is 0.1 to 0.65, desirably 0.15 to 0.5
It was set to 0.

[0009]

Next, the target material of the present invention will be specifically described with reference to examples. As a raw material powder, each having an average particle diameter shown in Table 1, a composition formula: Ta
A tantalum silicide powder of Si ₂ and a metal Ta powder were prepared, and the raw material powders were similarly blended in the proportions shown in Table 1, mixed with a ball mill for 12 hours, dried, and then the mixed powder having an outer diameter of 250 mm was prepared. Then, a cavity is filled in a carbon mold having a diameter of 130 mm × depth: 60 mm, and a predetermined temperature within a range of 1750 to 1950 ° C. in a vacuum or an inert gas atmosphere, and a pressure of 20 to The sintered body is hot-pressed under the condition of applying a predetermined pressure in the range of 30 MPa for one hour to remove the yellow TaC layer generated by the reaction with carbon on the surface of the hot-pressed sintered body. Also, a diamond grindstone is used to polish the surface of the diamond grindstone, and the diameter is 1: 1.
Each of the disk-shaped target materials 1 to 8 of the present invention was manufactured by finishing to a size of 25 mm × thickness: 5 mm.
Regarding the resulting target materials 1 to 8 of the present invention,
The structure of any of the cross sections was observed using an electron probe X-ray microanalyzer. As a result, it was confirmed that each of the cross sections basically consisted of a tantalum silicide phase and a metal Ta phase. The percentage was calculated. Further, the composition formula indicating the overall composition by chemical analysis: was measured x values of TaSi _x. The results are shown in Table 1. Table 1 also shows the theoretical density ratio.

Next, the target materials 1 to 8 of the present invention are used.
Were soldered to a pure copper backing plate using In-15% by weight Sn alloy solder, and charged into a reactive sputtering apparatus having a structure shown in a schematic longitudinal sectional view in FIG. Single crystal Si wafer having a diameter of 0.5 mm and thickness (fixed), distance between substrate surface and target material surface: 60 mm, substrate temperature: room temperature, reduced pressure inert gas atmosphere pressure: 1 Pa, Ar / N ₂ flow ratio : 8/2, applied power: RF500W, deposition time: 5 minutes to form a (TaSi _y) N _z film on the substrate surface in conditions.

For the purpose of comparison, each of them has a diameter of 12
A disk-shaped sintered metal Ta target material and a molten polycrystalline Si target material having a size of 5 mm × thickness: 5 mm are prepared as conventional target materials, and these target materials are supplied to the reactive sputtering apparatus of FIG. Under the same conditions, the substrate was charged into a pure copper backing plate in a soldered state. Substrate: single-crystal Si wafer having a diameter of 100 mm and a thickness of 0.5 mm (rotated at a speed of 10 rpm), the surface of the substrate and the surface of the target material Distance: 60 mm, substrate temperature: room temperature, reduced pressure inert gas atmosphere pressure: 1 Pa, Ar / N ₂ flow ratio: 8/2, applied power: RF500 W to any target material, film formation time: 5 minutes. Under the conditions, a (TaSi _y ) N _z thin film was formed on the substrate surface.

As described above, (TaSi _y ) formed using the target materials 1 to 8 of the present invention and the conventional target material.
The film thickness of the N _z thin film is measured at arbitrary 15 points over the entire deposition surface, and the Si / Ta atomic ratio of the portion is measured. The maximum value and the minimum value are picked up from the measurement result, and these values are picked up. The average of the measured values was calculated. The results are shown in Table 2.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

As can be seen from the results shown in Table 2, when the target materials 1 to 8 of the present invention are used, a (TaSi _y ) N _z thin film having a uniform thickness is relatively obtained as compared with the case where the conventional target material is used. It can be seen that the film can be formed at an extremely high deposition rate, the local variation of Ta and Si in the thin film on the film surface is extremely small, and the entire thin film is homogenized. As described above, according to the target material of the present invention, the (TaSi _y ) N _z thin film in which the local variation of the constituents Ta and Si on the film surface is extremely small and the film thickness is uniform is relatively obtained. Since the film can be formed at a very high film formation rate, industrially useful effects such as, for example, sufficiently satisfying high integration and large capacity of a semiconductor device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a principal part of a semiconductor memory element.

FIG. 2 is a schematic longitudinal sectional view illustrating a reactive sputtering apparatus.

FIG. 3 is a schematic longitudinal sectional view illustrating another type of reactive sputtering apparatus.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C22C 1/05 C22C 1/05 Z

Claims (1)

[Claims] 1. The structure is substantially composed of a tantalum silicide phase and a metal Ta phase, and the proportion of the tantalum silicide phase occupies 33 to 92% by area when observed with a micrograph of an electron probe X-ray microanalyzer. 90
With a% or more theoretical density ratio, the overall composition formula: when expressed in TaSi _x, 0.1 to x values in atomic ratio
A sputtering target material for forming a tantalum silicon nitride thin film, comprising a hot pressed sintered body satisfying 0.65.