JPH06322530A - Target for sputtering - Google Patents

Abstract

PURPOSE:To stablly form the thin film of excellent quality of Ti-Al alloy high in purity and low in oxygen content by constituting a Ti-Al sputtering target by the combination of a high purity Ti, Al and its diffusion reaction layer. CONSTITUTION:The target which is made of the high purity Ti and the high purity Al having >=99.99% purity and having the composition expressed by Ti1-xAlx (0<x<1) is used as a starting material at the time of forming a Ti-Al semiconductor device by sputtering method. As the structure of the target, the target having the diffusion reaction layer of Ti and Al between the high purity Ti and Al, or consisting of the diffusion reaction layer of Ti and Al and the high purity Ti layer, or consisting of only the diffusion layer of the high purity Ti and Al, or the diffusion reaction layer of Ti and Al and the high purity Al is used. By using this target, the Ti-Al thin film which is low in oxygen content and has high purity composition is formed by the sputtering method.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a crude composition ratio Ti of high-purity titanium having a purity of 99.99% or more and high-purity aluminum.
_{The present invention} relates to a sputtering target made of _1-X Al _X (0 <x <1).

[0002]

2. Description of the Related Art There is a sputtering method as one of film forming methods for semiconductor devices, and there are various kinds of materials for a sputtering target used for the method, but titanium and aluminum (Ti _1-x Al _x , 0 <x <1) are used. A material having an alloy composition is promising as one of them, and in particular, the appearance of a high-purity product (metal content of 99.99% or more) has been desired.

The general manufacturing methods can be roughly divided into two types, that is, a melting method and a powder metallurgy method. However, when manufacturing a sputtering target having a binary composition of Ti-Al, the former melting method has three major problems. There is.

The first problem is that it is difficult to control the composition of Ti-Al. This is because the melting points of titanium (Ti) and aluminum (Al) are very different, and the vapor pressure of Al is very high near the melting point of Ti.
This is due to the large amount of evaporation and the composition shift. However, among the melting methods, the arc melting method using an argon gas atmosphere is suitable as a melting method for suppressing the evaporation of Al because the atmospheric pressure is relatively high, but it is difficult to agglomerate due to the second problem described below. Is.

The second problem is the soundness of the ingot produced by melting. This is due to the melting of one end of the ingot (it is cooled from the bottom part that was melted and solidified earlier in time, but due to the cooling rate there is strain inside the ingot, resulting in cracks, cracks, and soundness. It is difficult to obtain a large ingot.

The cooling rate of the ingot is uniquely determined by the type of melting method and those melting methods,
Controlling the cooling rate is extremely difficult.

The third problem is that it is difficult to perform plastic working from the ingot to the predetermined shape. 8% by weight or less A
Ti containing 1 can be plastically worked, but if its content is more than that, it is very difficult. Ti-36 wt% Al can be processed if it is done very carefully and carefully, but it requires a great deal of time and labor for vacuum heat treatment and processing. Again 1
The isothermal forging method, in which the material is heated to about 000 ° C, can be plastically processed, but it requires special equipment and is processed at a very slow speed, resulting in poor productivity and is not easy to perform. .

The dissolution method has the above problems, and Ti-A
It is not easy to manufacture a sputtering target having a binary composition of 1 l.

The purpose of use may be such that the purity for heat resistance and oxidation resistance does not matter so much and the metal content purity is 99.9% or less.
In the case of a Ti-Al binary composition sputtering target in which the oxygen content may be large, it can be manufactured by the powder metallurgy method, and in reality, it is mainly provided.

However, when the purpose of use is high purity of 99.99% or more for semiconductor devices and the oxygen content needs to be controlled, the following problems occur in the production by the powder metallurgy method. Will occur.

1) Contamination of metal impurities mainly from constituent materials of equipment used in the crushing process.

2) A large increase in oxygen content resulting from the increase in surface area due to pulverization into powder.

3) It is difficult to sinter and solidify without being contaminated by the atmosphere or contact materials.

As described above, it is not easy to produce a high-purity material having a low oxygen content by either the melting method or the powder metallurgy method. In the case of manufacturing such a target, it is known that the target is provided as a mosaic target composed of necessary materials such as a split type and a composite type as illustrated in FIG. According to this method, the high purity of the constituent materials is maintained, and a Ti-Al target with a low oxygen content can be obtained by working in a vacuum or in a controlled atmosphere.

[0015]

When a mosaic target of a required constituent material such as a conventional split type or composite type is used, even if titanium and aluminum, which have similar sputtering efficiencies, are deposited. There is a deviation in the above composition. This deviation is due to the design of the mosaic shape of the sputtering target surface such as subdivision and subdivision
It is possible to suppress it to some extent, but it is not enough.

In addition, the target shape is not limited to a relatively simple shape such as a disk shape or a flat plate angle shape, but a ring shape or a complicated shape such as a mortar shape is used. It has to be taken into consideration that the surface shape changes from the initial target surface shape in the course of use (not a uniform decrease but a large number of sputtered specific parts decrease). Then, the compositional deviation in film formation becomes large. Therefore, in the correction of this, the thickness direction of the target must be taken into consideration, and it is necessary to take a very complicated shape, and there is a problem that the cost is greatly increased.

An object of the present invention is to solve the above problems easily and to provide a sputtering target of high purity Ti-Al binary composition.

[0018]

The present inventor has developed the present invention as a result of various studies and experiments in order to solve various problems of the conventional system as described above. The technical constitution of the present invention is as follows. , A sputtering target comprising high-purity titanium and high-purity aluminum, and having a diffusion reaction layer of titanium and aluminum at the interface between titanium and aluminum, and also the sputtering target of the present invention Is a sputtering target composed of a diffusion reaction layer of titanium and aluminum and high-purity titanium or high-purity aluminum, or a sputtering target composed only of the diffusion reaction layer of titanium and aluminum, and has a uniform film-forming composition. Since there is little difference in composition, a single layer target with only the diffusion reaction layer has a conventional mortar shape, etc. It increased more efficacy profile targets, thin films for high-quality stable semiconductor device can be easily obtained.

[0019]

In the magnetron sputtering apparatus, which is the mainstream of the current sputtering apparatus, it is known that the target is significantly corroded in the region where the plasma is locally converged. Even if the composition ratio of Al and Al matches the composition ratio of the film formation, local erosion occurs, so that either Ti or Al at the erosion site is largely eroded, and the composition of the film is the same as Ti on the target surface. It is known to deviate from the ratio of Al.

However, in the mosaic target having the diffusion reaction layer of the present invention, since the Ti-Al diffusion reaction layer formation work is performed in a high vacuum or in an atmosphere of high purity inert gas (argon), oxygen contamination occurs. Not only is it a high quality Ti-Al target, but it also has a reaction layer, so the surface area of titanium and aluminum alone is small compared to a mosaic type that combines titanium and aluminum, and the diffusion reaction Since the layer is on the surface, it has been found that the deviation of the composition of the film formed by sputtering is reduced.

In particular, in the case of a single layer having only the diffusion reaction layer, the target shape can be any of flat plate shape, ring shape and mortar shape, and it becomes possible to eliminate the deviation of the composition of the film formation. As a result, a good quality and stable thin film for semiconductor devices can be obtained.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the sputtering target of the present invention has a predetermined shape of Ti-Al2 on a surface of a predetermined shape using high-purity titanium and high-purity aluminum.
Ti and Al are arranged in a surface area ratio corresponding to the original composition ratio,
Moreover, a diffusion reaction layer of Ti and Al is formed at the interface. Also, a diffusion reaction layer of Ti and Al and Ti (FIG. 2), Ti and Al
Of the diffusion reaction layer of Al and that of Al and the diffusion reaction layer of Ti and Al (FIG. 3).

In the following examples, the composition ratio of Ti and Al is T
Since the atomic weight of i is 48 and the atomic weight of Al is 27, Ti
In the case where the atomic ratio of -Al is 1: 1, Ti is 64% by weight and Al is 36% by weight in terms of composition.

[0025]

【Example】

[Example 1] Tens of strips of high-purity titanium having a thickness of 1 mm and a length four times the width were prepared, and Ti-80 wt% Al was placed in a square container made of titanium. , Were arranged upright at predetermined intervals (shown in FIG. 5). Thereafter, high-purity aluminum was cast between the titanium plates in a vacuum furnace, heat treatment was performed at 800 ° C. for 4 hours to form a diffusion reaction layer, and finally finish cutting was performed to obtain a target. The cross section of this was observed. It was confirmed by analysis that a diffusion reaction layer was formed in a matrix of Al with a thickness of about 2 mm and it was a TiAl ₃ phase. In the initial design, Ti and Al were determined by the volume ratio so that Ti-80% by weight Al was added, and a predetermined heat treatment was applied to obtain pure Al and T.
A target of Ti-80 wt% Al with two layers of iAl ₃ layer could be obtained.

[Embodiment 2] Similar to Embodiment 1, the thickness is 1 mm.
Using strip-shaped high-purity titanium plates of (1), they were stood side by side at a predetermined interval so as to be Ti-63% by weight Al, high-purity aluminum was cast, and heat treatment was applied to finish the target to obtain a target. As a result of detailed observation and analysis, Ti-63 wt% which is a single layer of TiAl ₃ phase by diffusion reaction
An Al target was obtained (FIG. 3).

[Embodiment 3] In the same manner as in Embodiment 1, Ti is used.
8 in a vacuum furnace in which aluminum was cast using a plate material with a thickness of 1 mm of titanium so as to be -45 wt% Al.
After heat treatment was carried out at 00 ° C. for 4 hours, the temperature was further raised and two-step heat treatment was carried out at 1400 ° C. for 2 hours, followed by finishing work to obtain a target. As a result of cross-section observation and composition analysis, a Ti-45 wt% Al target of a single layer of Al-rich Ti-Al deviated from the stoichiometric ratio of 1: 1 was obtained by the diffusion method. (FIG. 3) [Example 4] Ti-36 wt% in the same manner as in Example 1
A plate material having a thickness of 1 mm of titanium was cast from aluminum so as to be Al, and the same two-step heat treatment as in Example 3 was performed to obtain a target. As a result of the observation, a single layer target of Ti-36 wt% Al having a stoichiometric ratio of 1: 1 was obtained (shown in FIG. 3).

[Embodiment 5] Using high-purity titanium, first, grooving of a portion corresponding to the amount of aluminum of Ti-15% by weight Al was performed, and thereafter, in a vacuum furnace.
Molten high-purity aluminum is cast into this groove portion (FIG. 4) and heat-treated at 800 ° C. for 4 hours to form TiAl.
After forming a _3- phase diffusion layer of about 2 mm, finish cutting is performed to form a TiAl ₃ diffusion layer and a Ti 2-layer Ti-1.
A target corresponding to 5 wt% Al was obtained (shown in FIG. 2).

Example 6 Using high-purity titanium, T
A groove corresponding to the amount of aluminum of i-36 wt% Al was grooved, and the same treatment as in Example 5 was performed.
A diffusion layer of TiAl ₃ phase was formed to a thickness of about 2 mm, and finishing was performed to obtain a diffusion layer of TiAl ₃ and a target corresponding to Ti-36 wt% Al of three layers of Al and Ti (see FIG. 1). It should be noted that in the above-mentioned embodiment, molten Al was used based on Ti, but a laminated plate of Ti and Al may be used.
Alternatively, a thin plate of Ti and Al may be used and rolled at the same time (Baumkuchen shape, pancake shape).

In order to suppress voids that may be generated due to this diffusion reaction, pressure treatment may be performed during the heat treatment, or pressure treatment or a pressure treatment may be performed at the end of the series of operations.
It may be subjected to heat or pressure treatment.

In the examples, Ti-36 wt% A was mainly used.
The composition of Ti and Al is Ti.
_It can be freely adopted in the range of _1-X- Al _X (0 <x <1). Note Ti-36 wt% Al corresponds to Ti ₁ -Al _1.

[0032]

EFFECT OF THE INVENTION In a mosaic target of high-purity titanium and high-purity aluminum, the ratio of the diffusion reaction layer to the entire target surface can be changed depending on the heat treatment conditions and the geometrical shape. When using a sputtering target having a layer,
It is expected that the composition deviation of the film formation will be reduced. In particular, for a single layer having only a diffusion reaction layer, it is possible to obtain a thin film for a semiconductor device, which is more effective with a deformed target such as a mortar-shaped target, has a uniform film-forming composition, and is stable. It has the effect of being able to.

Further, in the case of the target having no diffusion reaction layer as in the present invention, after sputtering, as shown in FIG.
Although there is a step at the boundary between Ti and Ti, the step does not occur in the target of the present invention, resulting in mild erosion as shown in FIG. 7, indicating that sputtering is uniformly and stably performed on the target surface. Not only the uniformity of the film-forming composition but also the effect and the effect that a stable thin film for a semiconductor device, which is of good quality, can be obtained with a high yield from the viewpoint of the film-forming process.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view of a circular target made of Ti, a Ti—Al diffusion reaction layer, and Al showing an example of the present invention.

FIG. 2 is a partial cross-sectional perspective view of a circular target including Ti and a Ti—Al diffusion reaction layer according to another example of the present invention.

FIG. 3 is a partial cross-sectional perspective view of a circular target including only a Ti—Al diffusion reaction layer according to another example of the present invention.

FIG. 4 is a partial cross-sectional perspective view of a circular target made of Ti and Al according to another example of the present invention.

FIG. 5 is a perspective view showing an example of assembling a rectangular target according to another example of the present invention.

FIG. 6 is a vertical sectional view showing an erosion state of a conventional target.

FIG. 7 is a vertical sectional view showing an erosion state of the target of the present invention.

[Explanation of symbols]

 Ti Titanium Al Aluminum Ti-Al Titanium / Aluminum Diffusion Reaction Layer 10 Titanium Container

Claims (4)

[Claims] 1. A sputtering target, comprising high-purity titanium and high-purity aluminum, and having a diffusion reaction layer of titanium and aluminum at the interface between titanium and aluminum. 2. A sputtering target comprising a diffusion reaction layer of high-purity titanium and high-purity aluminum and high-purity titanium. 3. A sputtering target, comprising only a diffusion reaction layer of high-purity titanium and high-purity aluminum. 4. A sputtering target, comprising a diffusion reaction layer of high-purity titanium and high-purity aluminum and high-purity aluminum.