JP2000128638A - Strontium ruthenate sintered body, method for producing the same, and sputtering target using the same - Google Patents

Abstract

(57) [Problem] To provide a good dielectric film when a strontium ruthenate sintered body is used as a sputtering target. A high-density sintered strontium ruthenate having a density of 3.5 g / cm ³ or more is obtained by using, as a raw material, a calcined strontium ruthenate powder synthesized from strontium carbonate and ruthenium oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a strontium ruthenate target for forming a strontium ruthenate film used for a memory for a computer by sputtering.

[0002]

2. Description of the Related Art As a capacitor of a next-generation semiconductor memory, it is conceivable to use ruthenium oxide for an electrode and BST (barium / strontium / titanium) for a ferroelectric film. I have. Therefore, it is desired to improve adhesion by sandwiching strontium ruthenate between them, and sputtering is used to form a strontium ruthenate film.

FIG. 1 is a schematic view of a general sputtering apparatus. Two counter electrodes (cathode (target) 3, anode 4) are placed in a vacuum chamber, and a high voltage is applied. Gas inlet
The Ar gas supplied by 2 generates a glow discharge, and the generated positive ions are accelerated in an electric field and collide with the surface of the cathode (target) 3 as a raw material. Therefore, atoms and molecules on the target surface are splashed with a momentum into a vacuum and deposited on the substrate 5. Therefore, if the target forming the cathode 3 is formed of a sintered body of strontium ruthenate, a strontium ruthenate film can be formed on the substrate 5. The method of forming a thin film in this way is called sputtering.

[0004] A strontium ruthenate target as a conventional target has been manufactured by mixing powders of strontium oxide and ruthenium oxide, followed by molding and firing.

[0005]

The above-mentioned sputtering is performed in a vacuum. At this time, if the degree of vacuum is low, the efficiency of the sputtering is reduced. However, in the conventional method of manufacturing a strontium ruthenate sintered body, since a high-density material cannot be manufactured, the target itself contains pores (air) therein, which hinders the conditions of high vacuum. . For this reason, the conventional strontium ruthenate target has a very low sputtering efficiency and is not practical.

Further, when strontium ruthenate is sputtered, strontium evaporates during sputtering, and the strontium in the sputtered film is reduced from the composition of the sputtering target, resulting in a problem that the characteristics are deteriorated. For this reason, the conventional strontium ruthenate sintered body could not be used as a sputtering target.

[0007]

According to the present invention, a high-density strontium ruthenate having a density of 3.5 g / cm ³ or more is obtained by using a calcined ruthenate strontium powder synthesized from strontium carbonate and ruthenium oxide as a raw material. This is to obtain a sintered body. Thereby, when the obtained sintered body is used as a sputtering target, a good dielectric film can be obtained.

Further, in order to use a strontium ruthenate sintered body as a sputtering target, the amount of strontium must be made excessive because strontium evaporates during sputtering. On the other hand, even if the amount of strontium is too large, strontium remains as an impurity after sputtering, so that the characteristics are deteriorated. From this, as a result of conducting various experiments, it was found that the molar ratio of strontium to ruthenium in the strontium ruthenate oxide suitable as a sputtering target was 1.1 to 1.3.

According to the present invention, the compounding ratio of strontium carbonate and ruthenium oxide is prepared by mixing strontium carbonate by 40 to 70% and ruthenium oxide by 60 to 30% by weight.
By controlling the calcination temperature and sintering temperature, the strontium in the sintered body can be reduced from 1.1 by mole ratio to ruthenium.
It is possible to manufacture a strontium ruthenate sintered body which is 1.3 times as large. When this sintered body is used as a sputtering target, a good dielectric film can be obtained.

Further, the calcination temperature is from 1100 to 1400
C is desirable. When the temperature is 1100 ° C. or lower, unreacted strontium carbonate remains, and the density of the sintered body decreases. 14
If the temperature is higher than 00 ° C., the grain growth increases and the sinterability decreases.

In the present invention, water and an organic binder are added to the calcined powder to form a slurry, mixed, and spray-dried. The powder is molded by the most suitable molding method from among molding methods such as die molding and cold isostatic pressing, in consideration of the desired shape and size of the sintered body. The molding pressure at this time to obtain a dense sintered body, 0.8ton / cm ² at a minimum, or preferably, when molded at 1.0 ton / cm ² or more.

The firing of the molded body is performed at 1500 to 1700 ° C. When the temperature is 1500 ° C. or lower, the density does not increase and it cannot be used as a sputtering target. Also,
If the temperature is 1700 ° C. or more, the metal reacts with the slab, and it becomes difficult to maintain the shape of the sintered body. In addition, strontium ruthenate usually has high reactivity with alumina often used as a firing jig, and therefore, zirconia or spinel is used as a firing jig.

[0013]

Embodiments of the present invention will be described below.

Example 1 60% by weight of strontium carbonate and 4 parts of ruthenium oxide
A 0% raw material was mixed with a ball mill to form a slurry, dried, and calcined at 1230 ° C. to obtain a strontium ruthenate calcination powder. Water and an organic binder were mixed with the calcined powder and spray-dried at 200 ° C. After press molding, sintering at 1600 to 1700 ° C. for 2 hours through a degreasing process, the resultant was ground to φ300 × 6t. The obtained sintered body had a density of 4.0 g / cm ^{3 and} could be used as a good target material.

Example 2 Strontium carbonate 60% by weight, ruthenium oxide 4
0% was mixed with a ball mill to form a slurry.
The calcination temperature was varied at 200 to 1400 ° C., and the average crystal diameter and sintered body density of strontium ruthenate were examined. As shown in Table 1, the density was 3.5 g / cm in each case.
³ or more.

On the other hand, as a comparative example, when a conventional strontium ruthenate sinter was produced by mixing strontium oxide and ruthenium oxide powder, molding and firing the mixture, the density was as low as 2.8 g / cm ³ , Had a large number of pores.

A target was prepared from the strontium ruthenate of the example of the present invention and the comparative example, and sputtering was performed with the apparatus shown in FIG. 1. In the comparative example, the degree of vacuum in the chamber was reduced, and the efficiency of sputtering was reduced. Was bad.

On the other hand, in the embodiment of the present invention where the density was 3.5 g / cm ³ or more, efficient sputtering could be performed.

[0019]

[Table 1]

Example 3 Strontium carbonate 60% by weight, ruthenium oxide 4
0% was mixed with a ball mill to form a slurry.
Calcination synthesis at 230 ° C. to obtain strontium ruthenate calcined powder. Mix water and organic binder with calcined powder,
Spray dry at 0 ° C. After press molding, sintering at 1680 ° C. for 2 hours through a degreasing process, the resultant was ground to φ300 × 6t. The molar ratio of strontium to ruthenium in the obtained sintered body was 1.20, which was a good target material.

Example 4 Strontium carbonate 60% by weight, ruthenium oxide 4
0% was mixed with a ball mill to form a slurry, and after drying, the calcination temperature was 1200 to 1400 ° C and the sintering temperature was 1600.
At 1700 ° C., and the amount of strontium in the strontium ruthenate sintered body was examined by ICP. The amount of strontium was shown as a molar ratio to ruthenium.

As shown in Table 2, the molar ratio of strontium to ruthenium in the sintered body could be controlled by adjusting the calcination temperature and the calcination temperature.

On the other hand, as a comparative example, one having a molar ratio of strontium to ruthenium of 1 was prepared.

Using these strontium ruthenates of the examples of the present invention and the comparative examples, sputtering targets were prepared, and sputtering was performed by the apparatus shown in FIG. As a result, in the comparative example, strontium was evaporated during use and the characteristics were deteriorated. On the other hand, the molar ratio of strontium to ruthenium is 1.1 to 1.3.
In the examples of the present invention set in the range, no decrease in characteristics during use was observed.

[0025]

[Table 2]

[0026]

According to the present invention, a high-density strontium ruthenate sinter having a density of 3.5 g / cm ³ or more is obtained by using strontium ruthenate calcination powder calcined from strontium carbonate and ruthenium oxide as a raw material. Obtainable. Further, when this sintered body is used as a sputtering target, a good dielectric film can be obtained.

Since the strontium ruthenate sintered body obtained by the present invention has a molar ratio of 1.1 to 1.3 times strontium with respect to ruthenium, even if strontium evaporates during sputtering, it is excellent. A strontium ruthenate film can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of a general sputtering apparatus.

[Explanation of symbols]

 1: vacuum pump 2: gas inlet 3: cathode (target) 4: anode 5: substrate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA09 AA26 BA09 GA08 GA14 4G048 AA01 AA05 AB01 AC02 AE05 4K029 CA05 DC05 DC09 DC12 5G303 AA10 AB20 BA09 CA01 CB32 CB43 DA01 DA05

Claims (4)

[Claims] 1. A has a chemical composition of strontium ruthenate, and a density of 3.5 g / cm ³ or more, strontium amount in the sintered body at 1.3 times 1.1 in a molar ratio with respect to ruthenium A strontium ruthenate sinter characterized by the above. 2. Strontium ruthenate comprising the steps of calcining and synthesizing strontium carbonate and ruthenium oxide to form a calcined strontium ruthenate powder, forming the calcined strontium ruthenate powder into a predetermined shape, and calcining the powder. A method for manufacturing a sintered body. 3. The strontium carbonate of 40 to 70% by weight.
And ruthenium oxide in a range of 60 to 30% by weight,
The method for producing a strontium ruthenate sinter according to claim 2, wherein the sintering is performed at a temperature of 1500 to 1700 ° C after the calcination synthesis at 00 to 1400 ° C. 4. A sputtering target comprising the sintered strontium ruthenate according to claim 1.