JPH0827571A - Method for producing strontium titanate target - Google Patents

Abstract

(57) [Summary] [Structure] Strontium titanate powder having an average particle size of 0.1 to 5.0 μm is molded by a press molding method, a casting molding method, or the like, and then sintered to obtain a sintered density of 4 ．
A strontium titanate target of 61 g / cm ³ or more is manufactured. [Effect] After sintering, there is no color unevenness due to partial nonuniformity of the composition, no cracks are observed during the manufacturing process, and a highly reliable target without cracks during sputtering can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sintering target used for forming a strontium titanate thin film by a sputtering method.

[0002]

2. Description of the Related Art In recent information society, SiO ₂ or SiN is used as a capacitor material for semiconductor memory.
Have been used. However, with today's increasing amount of information and higher integration of semiconductors, there is a demand for smaller area and larger capacity of semiconductor memories. As a capacitor material for satisfying this requirement, strontium titanate (hereinafter abbreviated as STO), which has a higher dielectric property than SiO ₂ or SiN, is drawing attention.

Such an STO thin film is obtained by sputtering an STO target, and this target is obtained by molding STO powder by using a pressing method or a casting method and then sintering it.

[0004]

However, in the STO sintered target obtained by such a conventional manufacturing method, the target composition is partially nonuniform after sintering, and spot-like color unevenness is observed in the bulk. However, there is a problem in that the cracks occur during the manufacturing process and the yield decreases. Further, even in a target product in which no problem was found during the manufacturing process, there was a problem in reliability that cracks were generated during sputtering.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have used STO powder having an average particle size of 0.1 to 5.0 μm, and By setting the density after sintering to 4.61 g / cm ³ or more, there is no color unevenness due to non-uniformity of the composition, and no cracks occur during the manufacturing process or during sputtering.
The inventors have found that a TO target can be manufactured, and completed the present invention.

Details of the method of manufacturing the STO target according to the present invention will be described below.

In the present invention, STO powder is used as a raw material, molding is performed by a pressing method or a casting method, and then sintering is performed. The STO sputtering target can be manufactured by bonding the thus obtained sintered body to a backing plate.

The STO powder used here can be obtained by mixing strontium carbonate powder and titanium oxide powder in a predetermined molar ratio, performing calcination, and crushing the obtained calcined powder. In addition, the pulverization referred to here is mainly intended to restore aggregated particles (secondary particles or more) to primary particles. The mixing molar ratio of the strontium carbonate powder and the titanium oxide powder is not particularly limited and can be adjusted according to the purpose. The STO powder particle size can be adjusted by selecting the average particle size of the strontium carbonate powder and the titanium oxide powder and setting the calcination temperature,
As a result, the average particle diameter of the primary particles of STO powder was 0.1
It is adjusted to ˜5.0 μm, but the range of 0.1 to 2.0 μm is more preferable in terms of moldability.

The molding method is not particularly limited, and the molding may be carried out by, for example, a press molding method, a casting molding method, or the like, and re-pressing treatment may be performed by a cold hydraulic pressing method.
The pressurizing condition at this time is not particularly limited, but a condition of a pressure of about 3 ton / cm ² for about 30 seconds is preferable in terms of moldability. At this time, an organic material-based binder agent may be mixed in order to further enhance the moldability.

A sintered target is obtained by sintering the compact thus obtained at a predetermined temperature for a certain period of time or longer. The sintering temperature may be 1200 ° C. or higher,
If it exceeds 1500 ° C, abnormal grain growth may occur due to over-firing, so it is preferable to sinter in the range of 1200 to 1500 ° C. The sintering time may be 3 hours or more, but abnormal grain growth may occur in the sintering for more than 10 hours, so 3 to 10 hours is preferable. The sintering atmosphere is not particularly limited, and it may be performed in oxygen, air, or reducing atmosphere. Then, the obtained sintered body is cut into a predetermined size and bonded to a backing plate to obtain a target product.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The particle size measurement in the present invention was carried out using a light transmission type particle size distribution analyzer (manufactured by Seishin Enterprise Co., Ltd.), and the value of 50% of the cumulative particle size distribution at that time was taken as the average particle size.

Example 1 Strontium carbonate powder and titanium oxide were prepared as raw material powders, adjusted to have a molar ratio of 1: 1 and then thoroughly mixed. Subsequently, calcination and pulverization were performed to give 0.5 μm, 2.0 μm, 3.5 μm, 4.
Four types of STO powder having an average particle size of 5 μm were prepared. After that, this STO powder was filled in a mold (150 mmφ), press-molded, and repressurized by a cold hydraulic pressing method. This molded body was sintered in an air atmosphere at 1400 ° C. for 4 hours using a firing furnace. The sintered body thus obtained was washed and then bonded to a backing plate to obtain a target product. The composition of the target at this time is 5 in terms of the ratio of Sr: Ti.
It was 0:50 (atm%).

Comparative Example 1 The average particle diameters of the strontium carbonate powder and titanium oxide and the calcination temperature were set different from those in the examples, and other conditions were 0.02 μm and 7. Two types of STO powder with an average particle size of 5 μm were prepared. Using these powders, molding, firing and bonding were carried out in the same manner as in the example to manufacture a target product. The composition of the target at this time is 50:50 (at
m%).

Comparative Example 2 2.0 μm as shown in Table 1 by the same method as in Example.
Two types of STO powder having an average particle diameter of m and 4.5 μm were prepared, press-molded, and subjected to re-pressurizing treatment by a cold hydraulic press method to obtain a molded body. The molded body was sintered under conditions different from those of the examples, and the obtained sintered body was washed and then bonded to a backing plate to obtain a target product. The composition of the target at this time was 50:50 (atm%) in terms of the ratio of Sr: Ti.

Using the STO powder of each powder particle size according to the above-described Examples and Comparative Examples, 10 targets were manufactured, and the density of the sintered body, the color unevenness of the sintered body, the manufacturing process, and The generation of cracks during sputtering was investigated. The density was measured by the Archimedes method, while the occurrence of cracks was visually observed. Table 1 shows the results.

[0016]

[Table 1]

As is clear from this result, in the case of the example, there was no color unevenness, no cracks were observed during the manufacturing process and during the sputtering, and good results were obtained. On the other hand, in the results of Comparative Examples 1 and 2, the occurrence of color unevenness of the sintered body or the occurrence of cracks during the manufacturing process and during the sputtering was observed, and the yield was lowered and the reliability as a target product was significantly increased. Shows that there is a problem.

[0018]

As described above, according to the present invention, STO powder having an average particle size of 0.1 to 5.0 μm is used and the density after sintering is 4.61 g / cm ³ or more. In addition, there is no color unevenness due to partial non-uniformity of composition after sintering, no cracks are observed during the manufacturing process, and cracks are not generated during sputtering.
The target can be manufactured.

Claims (1)

[Claims] 1. A method for producing a strontium titanate target having a sintered density of 4.61 g / cm ³ or more obtained by molding and sintering strontium titanate powder having an average particle diameter of 0.1 to 5.0 μm.