JPS61264173A - Production of sputtering target - Google Patents

Abstract

PURPOSE:To produce a sputtering target contg. slightly alkali metals such as Na by molding powder, subjecting the sintered compact to finish working and heat treating it under proper conditions in a vacuum furnace. CONSTITUTION:Powder of a starting material such as molybdenum silicide is molded by a powder sintering method such as hot hydrostatic pressing. The sintered compact is subjected to finish working to a prescribed shape and heat treated at >=800 deg.C in a vacuum furnace under <=10<-2>Torr. Thus, alkali metals such as Na and K in the starting material or those which entered the compact during the working are evaporated and removed from the compact and a sputtering target having a low alkali metal content and suitable for use in the production of a gate electrode with a stable threshold value is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a method for manufacturing a sputter target manufactured by a powder sintering method used when forming semiconductor electrodes by a sputtering method.

[Prior Art] In recent years, silicides of high-melting point metals such as molybdenum and tungsten, which have low specific resistance, have been used for gate electrodes of MOS type LSIs. To form such a film of high melting point metal silicide, a sputtering method using a target made of high melting point metal silicide is used.

Targets made of high melting point silicides, particularly molybdenum silicide, are generally made from powder obtained by pulverizing molybdenum powder and silicon powder, or molybdenum silicide ingots produced by melting, and are produced using powder sintering methods such as hot pressing or hot isostatic pressing. Manufactured by the binding method.

On the other hand, in addition to low specific resistance, the gate electrode is required to have a stable threshold voltage. It is known that the variation in threshold voltage is mainly caused by the movement of alkali metal ions such as Na in the gate oxide film.

Therefore, it is required that the target for electrode film formation does not contain alkali metals such as Na.

However, in addition to being contained in the target raw material, Na is easily mixed into the target during the target manufacturing process, for example from dust in the atmosphere, sweat from the human body, or grinding oil from polishing processes, contaminating the target. .

[Problems to be Solved by the Invention] The present invention solves the following problems:
The present invention provides a method for manufacturing a target using a powder sintering method.

[Means for solving the problem] The present invention provides a target molded and finished by a powder metallurgy method at a temperature of 10-2 Torr or less, preferably 10-
The present invention provides a method of evaporating and removing alkali metals by heat treatment at a temperature of 800° C. or higher, preferably 900° C. or higher in a vacuum furnace of 3 Torr or lower.

[Example] The present invention will be explained below with reference to Examples.

M is a molybdenum ingot with a purity of 99.98%.

S12. The raw materials were blended so as to be as follows and melted in a plasma arc furnace. The obtained alloy was pulverized using a vibrating pulverizer. This raw material powder was packed into a mild steel cylindrical can whose inner surface was sprayed with MO, vacuum degassed, sealed, and hot isostatically pressed at a pressure of 1,000 kg/CI2.

It was molded and sintered at a temperature of 1180° C. for 1 hour 3)-1r to obtain a target with a diameter of 240 mm and a thickness of 50 II m. This target was cut to a thickness of 10111111 mm using an electric discharge cutting machine, and then surface ground to form a disk having a thickness of 6 mm. From this disk, thickness 6mm, width 10mm,
A test piece with a length of 20 m was taken. One of the test pieces was broken in a clean room to expose the natural fracture surface, and the center was analyzed for Na and K by rMA. The results of the analysis were 22.2 and 2.2 compared to the standard sample.

Next, a test piece of the same shape taken at the same time was placed at a vacuum level of 10'.
Torr electric furnace, 800. 900. 1,00
A cleaning heat treatment was performed at 0 and 1,100° C. for 2.5 hours, and each test piece was broken in a clean room to expose the natural fracture surface, and IMA analysis was performed on the center of the specimen.

The results of the analysis are shown in Table 1. Heat treatment at 800°C reduces the Na content by about half, and at 900°C or higher it can be reduced to less than one-twentieth. The reduction effect on K is also large. This effect can be achieved by further reducing the content by increasing the degree of vacuum and extending the heat treatment time, but the degree of vacuum exceeds 10 to 2 Torr. and the reduction effect becomes worse, which is not desirable.

Table 1 [Effects of the Invention] As explained above, according to the production method of the present invention, the content of alkali metals such as Na mixed into raw materials or during the production process can be reduced.

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Claims (1)

[Claims] After being molded using the powder sintering method and finished into the desired shape, it is heated to 800°C in a vacuum furnace at 10^-^2 Torr or less.
A method for producing a sputter target, characterized by heat treatment at a temperature above.