JPH0313192B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a high-melting point metal silicide target, and in particular, a high-density target used for forming thin films such as electrodes and wiring materials of semiconductor devices. The present invention also relates to a method for producing a high-quality high-melting point metal silicide target. As a high melting point metal,
Mo, W, Ti, Nb, Ta, etc. are included, and Mo and W are particularly taken as representative examples here. This target is particularly useful for producing gate electrodes, source and drain electrodes of VLSI/MOS devices, and contacts and electrodes of various semiconductors.

[Background of the invention]

Electrodes or wiring of semiconductor devices, especially MOS/
Polysilicon has traditionally been used as gate electrodes in LSIs, but as MOS/LSIs become more highly integrated, signal propagation delays due to the resistance of polysilicon gate electrodes and source and drain electrodes have become a problem.
On the other hand, it is desired to use a material with a high melting point for the gate electrode in order to facilitate the formation of a MOS device by the self-alignment method. Under these circumstances, research is progressing on high-melting point metal gate electrodes and source and drain electrodes, which have lower resistivity than impurity-doped polysilicon, while research on high-melting point metal silicide electrodes, which prioritize compatibility with silicon gate processes, is progressing. It is actively progressing. Promising practical examples of such refractory metal silicides are molybdenum silicide (MOSix) and tungsten silicide (WSix).

Sputtering methods and electron beam evaporation methods are effective methods for forming refractory metal silicide thin films for electrodes or wiring of semiconductor devices. The sputtering method is a method in which a target plate is bombarded with argon ions to release metal, and the released metal is deposited on a substrate facing the target plate. The electron beam evaporation method is a method in which an ingot evaporation source is melted by an electron beam and vapor deposition is performed. In any case, the purity and other properties of the produced film depend on the purity, composition, sputtering characteristics, etc. of the target plate or evaporation source.

Hereinafter, in this specification, "target" means
All refractory metal silicide articles shaped into plates or other forms as sputtering sources or vapor deposition sources are covered.

[Conventional technology and its issues]

JP-A-60-66425 discloses a method for producing a molybdenum silicide target, specifically using molybdenum as the high melting point metal. Here, we start with a process of mixing specially prepared high-purity molybdenum powder and commercially available high-purity silicon powder, and then (1) pressure molding (cold isostatic processing method) and (2)
Produce a sintered body through the process of sintering, followed by (3)
A MoSix ingot is produced by an electron beam melting process, and (4) the ingot is given a desired shape by a plastic working (hot extrusion method or vacuum forging method) process, and finally cutting, surface finishing, etc. The target is manufactured by performing finishing processing.

The target produced by the above method has extremely high purity, with trace amounts of alkali metal elements and radioactive elements harmful to semiconductor devices being reduced, and is useful for producing gate electrodes and the like.
However, there are the following problems regarding the process: (a) As the process goes through the four steps of cold isopressure pressing, sintering, electron beam melting, and plastic working as mentioned above, there are many steps. Each process itself requires labor, time, and expensive equipment, making it unsuitable for industrial-scale production.

(b) There is a lot of silicon volatilization loss during electron beam melting, which makes it difficult to prepare MOSix x.

On the other hand, apart from the above method, there is a method of manufacturing using only a sintering method that does not involve a melting process, but it has been difficult to manufacture high-density targets made of high melting point metal silicide using the conventional sintering method. In addition to this, Si loss is large, and local variations in composition are the main problem.

The loss of Si is large and it is economically disadvantageous.

In addition, the structure (crystals) becomes coarser,
The properties of the sputtered film deteriorate.

Particles often occur during spatter.

There is a drawback.

For this reason, there is a problem in that the sputtering characteristics of the manufactured target are deteriorated and a good quality thin film cannot be formed.

It is an object of the present invention to solve the above-mentioned problems and to produce a high-quality refractory metal silicide target by a method suitable for industrial production.

[Means to solve the problem]

The present inventors completely abandoned the four steps of cold isopressure pressing, sintering, electron beam melting, and plastic processing, and made high-density metal silicide powder after synthesis using only a uniaxial compression molding process. We have repeatedly investigated the mochikisu sintering method. We have discovered that the fundamental reason why conventional sintering methods cannot produce high-quality targets is that a liquid phase is generated during sintering. Using relatively low temperature conditions where no liquid phase occurs,
It has been found that high-quality targets can be efficiently produced by solid-phase sintering using a hot press at high press pressure and high vacuum.

The generated target not only has a high density ratio of 97% or more, but also has a uniform composition and a dense structure, and by appropriately selecting the starting material, it can be made of extremely high purity. It was found to be of excellent quality with little particle generation.

Thus, the present invention provides uniaxial compression molding of high melting point metal silicide powder under the conditions of a temperature of 1000 to 1300°C, a high vacuum of 10 ^-5 to 10 ^-6 mbar, and a high press pressure of 250 to 600 Kg/ ^cm2 . The present invention provides a method for producing a high-melting point metal silicide target, which is a solid-phase sintered product and has a density of 97% or more.

Preferred high melting point metals are molybdenum or tungsten.

Preferably, the high melting point metal silicide powder is produced by mixing the high melting point metal and silicon powder in a predetermined ratio, synthesizing the silicide under high temperature vacuum, crushing and classifying the synthesized silicide, and adding silicon powder to the synthesized silicide powder. It is obtained by mixing.

[Specific description of the invention]

First, an example of synthesis of high melting point metal silicide powder will be explained. High melting point metals such as tungsten and molybdenum and silicon powder raw materials include:
Use materials with low radioactive element and low alkali metal content. Such raw silicon powder having a purity of 9N or higher or easily commercially available. Recently, the alkali metal content of raw material high melting point metal powder has also increased.
Technology has been established to prepare highly purified products of 5N or higher with a radioactive element content of 1000 ppb or less and a radioactive element content of 100 ppb or less. This method involves dissolving conventionally commercially available high melting point metals or their compounds to produce an aqueous solution, purifying the aqueous solution, crystallizing high melting point metal crystals, and solid-liquid separation, washing and drying of the crystals. After that, high-purity high-melting point metal powder is prepared by heating and reducing the powder. Further, by subjecting these powders to purification treatment such as redissolution, even higher purity can be obtained.

These raw material high melting point metal powders and WSix, MoSix
etc. under a predetermined ratio of silicon powder corresponding to V
They are mixed using a mold mixer or the like, and heated and synthesized, for example, in a vacuum resistance furnace. 10 ^-3 ~ ^{10 -5} mbar×
Synthesis is carried out at a temperature of 1050 to 1250°C for a sufficient period of time according to the following formula: W (Mo) + xSi → WSix (MoSix) In this way, carmella-like silicide (WSix,
MoSix) is synthesized.

The synthetic silicide is pulverized using a vibrating mill or other pulverizer, and classified into 35 to 45 mesh particles to obtain synthetic silicide powder.

Here, compensation silicon is added corresponding to the volatilization loss of silicon throughout the process. Preferably, the compensating silicon is also of the same size as the synthetic silicide powder. The synthetic silicide powder and the additional silicon powder are thoroughly mixed by wet mixing using, for example, a V-type mixer. after that,
After sufficient washing and vacuum drying, a high melting point metal silicide powder suitable for use in the subsequent uniaxial compression molding process can be obtained.

Uniaxial compression molding is performed at 10 ^-5 to ^{10 -6} mbar, in order to produce solid phase sintered products with a density ratio of more than 97%.
Preferably a high vacuum atmosphere of 10 ^-6 to 5 x 10 ^-6 mbar, a relatively low temperature of 1000 to 1300 °C, preferably 1200 to 1300 °C and 250 to 600 Kg/cm ² , preferably 350 to 500 Kg/cm ² It is carried out by a hot press capable of applying high press pressures of .

The high-melting point metal silicide powder is placed in a mold, the temperature is started to rise, and once a target temperature of 1000 to 1300°C is reached, that temperature level is maintained and application of a predetermined constant high press pressure is started. The molding material is gradually reduced in thickness as press pressure is applied, but beyond a certain point the material thickness reaches a certain level and is no longer reduced in thickness. The press is stopped after fully confirming this saturated state of thickness reduction. Generally, hot pressing is completed in 1 to 2 hours.

After that, the target is completed by removing burrs, etc., and if necessary, performing finishing processes such as surface finishing.

The target obtained has a high density ratio of 97% or more, and has extremely high purity with a radioactive element content of less than 10 ppm, an oxygen content of less than several hundred ppm, and an alkali and other metal content of less than 10 ppm. I can do it.

One of the characteristics of this target is that the oxygen content is low, ranging from 50 to 250 ppm. The low oxygen content is
This is because the deoxidation reaction of Si+O→SiO(g)↑ progresses in the high-temperature pressurizing process.

The target of the present invention is a solid phase sintered product since it is carried out at relatively low temperatures of up to 1300°C. However, because much higher pressing pressures are applied than conventionally, the resulting targets have a high density ratio of over 97%. By appropriately selecting starting materials, extremely high purity can be obtained. Because it is solid-phase sintered, the composition is uniform and the structure is dense, and there are fewer particles during sputtering.
It is of excellent quality.

Example 1 8.2 kg of tungsten powder with a purity of 5N and 2.6 kg of silicon powder with a purity of 5N were mixed in a V-type mixer, and tungsten silicide was synthesized in a vacuum resistance furnace at 1200°C x 10 ^-4 mbar. The synthesized carmela-like silicide was pulverized by a vibration mill and then classified into 42 mesh under. Similarly to this
42 Add 0.8Kg of mesh under silicone powder,
Powder mixed by V-type mixer is 187mmφ×150mm
Place in a mold with dimensions of 10 ^-5 mbar x 1200℃ x
Hot pressing was carried out for 3 hours under the condition of 350 kg/cm ² .
The density ratio of the obtained target was 97%.

Example 2 15.2 kg of tungsten powder with a purity of 5N and 4.8 kg of silicon powder with a purity of 5N were mixed in a V-type mixer, and tungsten silicide was synthesized in a vacuum resistance furnace at 1200°C x 10 ^-4 mbar. The synthesized carmela-like silicide was pulverized using a vibration mill and then classified into 42 mesh under. Similarly to this
Added 1.4Kg of silicone powder from 42 mesh under,
Powder mixed by V-type mixer is 254mmφ×150mm
Place in a mold with dimensions of 10 ^-5 mbar x 1300℃ x
Hot pressing was carried out for 3 hours under the condition of 520 kg/cm ² .
The density ratio of the obtained target was 99.9%.

Example 3 6.2 kg of molybdenum powder with a purity of 5N and 3.7 kg of silicon powder with a purity of 5N were mixed in a V-type mixer, and molybdenum silicide was synthesized in a vacuum resistance furnace at 1200°C x 10 ^-4 mbar. After pulverizing the synthesized carmela-like silicide using a ball mill.
It was classified into 42 mesh under. Similarly 42
Added 0.2Kg of mesh under silicon powder,
Powder mixed by V-type mixer is 187mmφ×180mm
Place in a mold with dimensions of 10 ^-5 mbar x 1300℃ x
Hot pressing was carried out for 3 hours under the condition of 350 kg/cm ² .
The density ratio of the target obtained was 97%.

Example 4 12.4 kg of molybdenum powder with a purity of 5N and 7.4 kg of silicon powder with a purity of 5N were mixed in a V-type mixer, and molybdenum silicide was synthesized in a vacuum resistance furnace at 1200°C x 10 ^-4 mbar. After pulverizing the synthesized carmela-like silicide using a ball mill.
It was classified into 42 mesh under. From this, 4
Kg was taken out, 0.1 Kg of silicon powder of 42 mesh under was added to it, and the mixed powder was put into a mold with dimensions of 286 mmφ x 150 mm using a V-type mixer.
Hot pressing was carried out for 3 hours under the conditions of 10 ^-5 mbar x 1300°C x 520 kg/cm ² . The density ratio of the obtained target was 99.9%.

〔Effect of the invention〕

In the present invention, since the target is manufactured by solid-phase sintering, 1 Si loss is small, the composition is uniform, the composition can be easily adjusted, and it is economically advantageous.

2 In addition to 1., the structure (crystals) becomes denser, which improves the properties of the sputtered film.

3. Fewer particles are generated during spatter.

4 By improving the density ratio of the manufactured target, the strength of the target increases and cracks and
No chipping occurs and the target life is extended.
Possible gaseous impurities are also reduced.

5 High purity targets can be produced.

Claims (1)

[Claims] 1. High melting point metal silicide powder is heated at a temperature of 1000 to 1300°C, under a high vacuum of 10 ^-5 to 10 ^-6 mbar, and at a temperature of 250 to 250 mbar.
Production of a high melting point metal silicide target that is a solid phase sintered product with a density of 97% or more, characterized by solid phase sintering by uniaxial compression molding under high press pressure conditions of 600 Kg / cm ² Method. 2. The method according to claim 1, wherein the high melting point metal is molybdenum or tungsten. 3 High melting point metal silicide powder is produced by mixing high melting point metal powder and silicon powder at a predetermined ratio, synthesizing silicide under high temperature vacuum, and pulverizing the synthesized silicide.
The method according to claim 1, which is obtained by classifying and mixing synthetic silicide powder with silicon powder.