JP2706635B2 - High purity titanium target for sputtering and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-purity titanium target for sputtering and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a thin film in a semiconductor device, a vacuum deposition method having a deposition mechanism, a sputtering method utilizing sputtering of a target by an inert gas ion, a CVD method and an ion plating method are known. However, in practice, a sputtering method is mainly used. The sputtering method is a method in which ions such as argon are bombarded against a target plate to release a metal, and the released metal is deposited on a device substrate to form a thin film. Therefore, the purity of the formed film, the uniformity of the film thickness, etc. The properties of
It depends on the purity, structure (particle size, orientation, etc.) of the target plate material, sputtering conditions, and the like.

The properties, such as specific resistance, that are practically required for a sputtering film are determined to some extent mainly by limiting the purity of a target used.
In addition, the uniformity of the film thickness and the soundness of the film (the uniformity of the particle diameter in the film and the film thickness after the film formation, and the film quality such as specific resistance and reflectance) greatly depend on the device characteristics and the target structure. It is well known that control of the structure of a target has a great effect on the product yield, including the case of an Al target. However, Ti has an hcp structure, and is liable to cause twin deformation and exhibits a texture. Furthermore, in the case of high purity (4N5, ie, 99.995% or more), recrystallization is easy, so that control of particle size and orientation is not easy.

[0004]

Problems to be Solved by the Invention Problem 1. In the sputtering method mainly used as a film forming method of a semiconductor device, the material of the sputtering target is,
There are many types depending on the purpose of use, and as one of them, a high-purity titanium target is often used. By the way, generally, undesired fine particles may be scattered at the time of film formation in the sputtering method, and these fine particles are deposited on the device substrate to form particles. Such particles cause defects such as disconnection in the device. The same phenomenon occurs in high-purity titanium, and reduction of the particles is desired.

Problem 2. When a target is sputtered to form a film on a target substrate, uniformity of the film thickness is important for improving productivity, and further improvement of a high-purity titanium target is desired. In particular, when used as a contact material, it is important to cover holes in the device. For the purpose of improving the step coverage, a collimator is inserted or sputtering at a low pressure is aimed at. In these cases, holes can be covered more efficiently as the component in the normal direction of the target increases among particles scattered during sputtering. However, in each case, the “number of particles contributing to film formation / input power” (sputter rate) is lower than in the normal case, and it is expected that higher power will be input in the future. Since it is known that the number of particles increases as the input power increases, it is desirable that the sputtering rate be improved even when the input power is suppressed.

Problem 3. In order to suppress the particles, improve the uniformity of the film thickness, and improve the step coverage, it is considered that control of the crystal grain size and the orientation of the polycrystal is an effective method. In particular, when a collimator is used for the purpose of improving step coverage, by controlling the orientation of the crystal grains present in the target, a normal component in the particles scattered by sputtering (a component contributing to film formation). , The sputtering rate increases.
When the closest surface is strongly oriented, the distribution of scattered particles has a small component in the normal direction. That is, there is little possibility of contributing to the film formation, but rather there is a possibility of forming a film on the target due to the positional relationship with other crystal grains (shadowing effect).
Therefore, by not aligning the closest-packed surface (0002), the component in the normal direction increases and the shadowing effect decreases.
As a result, spattering can be performed by controlling the input power, thereby reducing particles. That is, it is considered that the generation of particles is controlled by controlling the refinement and orientation of the crystal grains, and the step coverage and the sputtering yield can be simultaneously improved. The crystal grain size can be controlled to some extent by optimizing the material processing method and the degree of processing, and the heat treatment (heat treatment for recrystallization), but there is a limit, and the refinement (average particle size 20 μm) is possible.
m or less) is generally difficult to establish. Further, the higher the purity, the easier the crystal grains are to recrystallize and grow, so that the conditions for miniaturization become more severe. Also,
Since the orientation varies depending on the processing method, the degree of processing, and the heat treatment, it is generally difficult to obtain the particle size and the orientation at the same time for a predetermined purpose.

[0007] Normally, a Ti plate material has a texture and the close-packed (0002) plane is oriented. Further, the particle size depends on the impurity amount, and the particle size can be reduced as the impurity amount increases. That is, as the purity is increased, the plastic working becomes easier and the substantial working degree becomes smaller, so that a difference occurs in the grain size due to the same plastic working and heat treatment. In spite of this general theory, it has been considered that there is a great demand for purity in a sputtering target, and it is difficult to reduce the grain size and control the orientation while maintaining the purity.

The present invention achieves the above problems by miniaturizing crystal grains which are effective in suppressing the generation of particles, and simultaneously controlling the orientation to achieve an improvement in step coverage and sputtering rate. It is an object of the present invention to provide a high-purity titanium target for sputtering and a method for producing the same, which can solve the above problems.

[0009]

In order to achieve the above object, a high-purity titanium target for sputtering according to the first invention of the present invention has a purity of 99.995% or more (however, a metal component is used as an impurity). The average grain size is 20 μm or less, and the orientation of the crystal surface parallel to the outer surface of the target is I (101) / (0002)> 0.5 [I (hk
i1): Diffraction intensity of (hkill) plane by X-ray circuit folding measurement]. Further, the method of manufacturing a high-purity titanium target for sputtering according to the second invention of the present invention is a method of manufacturing a high-purity titanium bulk material having a purity of 99.995% or more (however, a metal component as an impurity) at 600 ° C.
It is forged below, and then rolled at 450 ° C. or less to produce a high-purity titanium plate material having a purity of at least 99999% and an initial hardness Hv (Vickers hardness) ≧ 130, which is heat-treated to control the grain size and orientation. It is characterized by doing.

The present invention will be described in further detail.
Forging and rolling are performed on a molten ingot having coarse crystal grains with high-purity titanium of 9.995% or more (however, a metal component as an impurity) to obtain a predetermined thickness suitable for a sputtering target material. Intermediate materials having various hardnesses Hv (Vickers hardness) are obtained depending on the temperature at the time. By heat-treating the intermediate materials having various hardnesses, the particle size and the orientation as the target material are determined. Hardness before heat treatment (hereinafter referred to as initial hardness)
There is a strong correlation between the particle size and orientation after heat treatment.

Then, first, as a result of intensive studies to obtain the relationship between the working temperature of forging and rolling and the initial hardness, the values shown in Table 1 were obtained. From these results, it was found that if the forging temperature was 600 ° C. or less and the rolling temperature was 450 ° C. or less, the initial hardness Hv ≧ 130. Table 1
The hardness (Hv) of the high-purity titanium sheet material obtained by forging and rolling at various temperatures is shown.

[0012] Table 2 Changes in initial hardness and grain size / orientation due to heat treatment Initial hardness Hv = 160 Hv = 130 Hv = 110 Heat treatment temperature Particle size Orientation Particle size Orientation Particle size Orientation −−−−−−−−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−− 400 ° C 05μm <0.5 10μm <0.5−> 0.5 450 ° C 08μm> 0.5 14μm> 0.5 −> 0.5 500 ° C 12μm> 0.5 17 μm> 0.5 − <0.5 550 ° C 16 μm> 0.5 20 μm> 0.5 25 μm <0.5 600 ° C 20 μm <0.5 25 μm <0.5 30 μm <0.5 −−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−−−−−−

[0013]

In the high-purity titanium target according to the present invention, a molten ingot having coarse crystal grains is subjected to forging at a temperature of 600 ° C. or less and rolling at a temperature of 450 ° C. or less or plastic working equivalent to the following. Action is obtained. 1. Recrystallization by heat treatment starts at a low temperature, and control of subsequent crystal grain growth becomes easy. 2. After the heat treatment, the orientation of the densest surface (0002: the scattering direction of particles scattered during sputtering is not concentrated in the normal direction) indicated by (0002) is suppressed. 3. There are heat treatment conditions that have an average particle size of 20 μm or less and do not orient the close-packed surface.

[0014]

Embodiments of the present invention will be described below.

Embodiment 2 FIG. Forging at 600 ° C using the same ingot as in Example 1, and rolling at 450 ° C,
A plate material having a thickness of 10 mm and an initial hardness Hv = 130 was obtained. To this plate
Heat treatment at 500 ° C. × 1 hour was performed to obtain a sputtering target. Observation of the crystal grain size of the target revealed that the orientation was> 0.5 at about 20 μm. This target was sputtered with the same apparatus as in Example 1 under the same initial conditions and operating conditions, and the number of generated particles was examined. As a result, a very good result of 36 particles was obtained at a cumulative film thickness of 500 μm.

Comparative Example 1 Forging at 700 ° C using the same ingot as in Example 1, and rolling at 550 ° C,
A plate material having a thickness of 10 mm and an initial hardness Hv = 90 was obtained. 5 on this plate
Heat treatment was performed at 00 ° C. × 1 hour to obtain a sputtering target. The crystal grain size of this target was about 35 μm and the orientation was <0.5. This target was sputtered in the same apparatus as in Example 1 under the same initial conditions and operating conditions, and the number of generated particles was examined.
It was an unfavorable result of 100 pieces at 500 μm.

Comparative Example 2 Forging at 700 ° C using the same ingot as in Example 1, and rolling at 550 ° C,
A plate material having a thickness of 10 mm and an initial hardness Hv = 90 was obtained. 6 on this plate
Heat treatment was performed at 00 ° C. × 1 hour to obtain a sputtering target. The crystal grain size of this target was about 45 μm and the orientation was> 0.5. This target was sputtered in the same apparatus as in Example 1 under the same initial conditions and operating conditions, and the number of generated particles was examined.
The result was not good at 120 pieces at 500 μm. Table 3 shows the results of Examples and Comparative Examples described above. Table 3 Time-dependent change in the number of generated particles depending on the target characteristics (number / 6-inch wafer) Cumulative film thickness (μm) Target 10 50 100 200 300 400 500 (average particle size, orientation) −−−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−− Comparative Example 1 to 35 μm, I <0.5 15 20 25 36 48 70 100 Comparative Example 2 to 45 μm, I > 0.5 8 10 36 50 80 90 120 Example 2 ≦ 20 μm, I> 0.5 8 8 14 16 16 24 36 Example 1 ≦ 20 μm, I <0.5 8 10 16 20 24 32 50 −−−−−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−− Particles of 0.3 μm or more present on the wafer when TiN is formed to a thickness of 0.1 μm on the wafer. Was measured and counted. As is clear from Table 3, Ti having an average particle size of 20 μm or less is used.
When the target was used, it was found that the number of generated particles was suppressed, and that the orientation was significantly suppressed if the orientation was> 0.5.

Experimental Example Using the targets used in Comparative Example 1 and Example 2 (shown in FIGS. 1 and 2, respectively), the beam angle distribution of sputtered particles and the deposition rate when a collimator was inserted were measured. And compared. Each result is shown in FIG. 1 and FIG. As is clear from FIG. 1 showing the beam angle distribution, the target according to the embodiment of the present invention has a larger component in the normal direction than the target according to the comparative example, and it is recognized that the step coverage becomes better. Further, as is clear from FIG. 2 showing the deposition rate when the collimator is inserted, the deposition rate of the target according to the embodiment of the present invention is higher than that of the target according to the comparative example. As described above, it is known that the number of generated particles increases as the input power increases. However, it has been shown that the target according to the embodiment of the present invention can form a film with the input power suppressed.

[0019]

As described above, in the target according to the present invention, the crystal grains of high-purity titanium are refined and the orientation is controlled. As a result, particles are generated in the semiconductor device manufacturing process. Is suppressed and the step coverage is improved due to an increase in the component in the normal direction, so that the sputtering yield is improved. Therefore, by applying the present invention to a sputtering target, the product yield can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a beam angle portion of a Ti target according to an example of the present invention and a comparative example.

FIG. 2 is a graph showing a deposition rate when a collimator is inserted with a Ti target according to an example of the present invention and a comparative example.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location C22F 1/00 685 8719-4K C22F 1/00 685A 8719-4K 685Z 686 8719-4K 686A 691 8719- 4K 691B 694 8719-4K 694B

Claims (3)

(57) [Claims] Claims: 1. An average particle size of not less than 20.mu.m with a purity of not less than 99.995% (but an impurity is a metal component),
And the orientation of the crystal surface parallel to the target outer surface is I (1
01) / (0002)> 0.5 [I (hki1): X
Diffraction intensity of (hkil) plane by line circuit folding measurement]. 2. A bulk material of high-purity titanium having a purity of 99.995% or more (but an impurity is a metal component) is 600
Forging below 450 ° C. and then rolling below 450 ° C. to produce a high purity titanium plate with a purity of at least 99.995% and an initial hardness Hv (Vickers hardness) ≧ 130, and heat-treating it to obtain a grain size and orientation. A method for producing a high-purity titanium target for sputtering, characterized by controlling the properties. 3. The heat treatment after forging and rolling is performed by 50.
The method for producing a high-purity titanium target for sputtering according to claim 2, wherein the method is performed at 0 ° C (± 50 ° C) for 1 hour.