JPH07122082B2 - Hot press mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot pressing mold used for sintering metal powder and ceramic powder.

[0002]

2. Description of the Related Art In order to obtain a sintered body such as a metal powder or a ceramic powder, the following method has been conventionally used. That is, first, an outer cylinder made of a carbon-bonded carbon fiber composite material (C / C composite material) is prepared, and an inner cylinder to be provided on the inner surface thereof is made of a heat resistant material such as graphite. Then, the outer cylinder and the inner cylinder are set in an appropriate induction furnace in a predetermined fitting relationship to obtain a required hot pressing mold. Then, a powdered material to be sintered or a preformed material to be sintered is loaded into the hot pressing mold, and pressure sintering is performed under various conditions such as a predetermined temperature, time and pressure. By doing so, a desired sintered body is obtained. However, according to this conventional method, pitches and charcoal are not added during the pressure sintering process described above.
The harmful elements from the outer cylinder of the mold made of the C / C composite material accumulated in the oxidization process and the like infiltrate into the sintered body in a thermal diffusion manner, and significantly deteriorate the various characteristics of the sintered body. Alternatively, it is the current situation that a satisfactory sintered body cannot be obtained due to a decrease in its purity.

[0003]

The object of the present invention is to clarify the cause of adverse effect on the sintering of such metal powder or ceramic powder, and to produce a dense and high-purity sintered body. To provide a mold.

[0004]

[Means for Solving the Problems] Examples of the metal sintered body produced by hot pressing include simple metals such as tungsten, molybdenum, titanium, rhenium, hafnium, chromium, and cobalt, and metal compounds such as silicides of the above metals. Can be mentioned. One of the specific uses of high-purity substances among these simple metals and metal silicides is
It is to be used as a wiring material for LSI as a sputtering target material. By the way, since there is such an application, the following various impurity contents in the hot pressing mold for the metal simple substance or metal silicide, which should be of high purity, are set to a predetermined value or less. Is needed. That is, an alkali metal which is ionized in a semiconductor element and easily moves in the gate insulating film to deteriorate MOS interface characteristics; iron, aluminum, chromium, nickel, etc. which cause interface states or junction leakage It is necessary to set the content of impurities such as various metals; and vanadium that acts as a reducing agent to a predetermined value or less.

On the other hand, in the flexible ceramic body produced by hot pressing, there is a ceramic target material used for sputtering as well as metal, which requires high purity. Such a ceramic target material is used as a thermal head, a transparent conductive film, a protective film, etc., and is also advantageous for rust prevention of various metals, surface strengthening, solar heat collectors, window frame materials for amorphous solar cells, etc. Is what is used. By the way, in order to exert the function of the thin film here, the material needs to maintain a certain degree of purity. Then, for this purpose, it was found that each impurity contained in the hot pressing mold has a specific critical impurity content rate.

Therefore, in order to obtain a dense and high-purity sintered body, it is necessary to hot-press the ultrafine powder raw material without adding a sintering aid harmful to the final product. At the same time, the sintering treatment must be performed so that the thermal diffusion of impurities from the hot pressing mold does not occur.

Therefore, what has been taken in accordance with the present invention is that the impurity content of the C / C composite material, which is the base material of the hot pressing mold, is 900 ppm or less, and that the heat diffusion from the hot pressing mold is specified. To reduce harmful elements to a certain level or less.

As one of the specific examples of the present invention, as a result of investigation and research on the cause of junction leakage of semiconductor electrodes, the following was found in the case of a sputtering target material manufactured by the hot pressing method. That is, the iron content of the C / C composite material, which is the outer cylinder of the mold, is 80 ppm or less; the aluminum content is 90 ppm or less; the nickel content is 1
It has been found that the trouble does not occur when the content of chromium is 5 ppm or less; the content of chromium is 10 ppm or less; and the content of vanadium is 30 ppm or less. At the same time, research and study were also conducted on the effect of alkali metals that cause deterioration of the interface characteristics of the MOS, and as a result, the sodium content of the C / C composite material, which is the outer cylinder, was 25 ppm or less. It was also found that no problem occurs when the potassium content is 25 ppm or less.

However, when the total content of impurities contained in the C / C composite material, which is the outer cylinder of the mold used for hot pressing, exceeds 900 ppm, gasification of the impurities causes the formation of the above-mentioned specific impurities. Even if the content is below a certain amount, its diffusion rate increases,
As a result, it causes trouble. Therefore, the total content of the impurities should be 900 ppm or less.

Also, regarding the ceramic target material such as the thermal head, the transparent conductive film and the protective film, the C / C which is the outer cylinder of the hot press mold used in the production thereof.
In the composite material, the iron content is 80 ppm or less; the aluminum content is 90 ppm or less; the nickel content is 15 ppm or less; the chromium content is 10 ppm or less; the vanadium content is 30 ppm or less; and the total impurity content. When the amount was 900 ppm or less; it was confirmed that the trouble of contamination by impurities was drastically reduced. Similarly, in addition to target materials, it is used in the field of electronic materials.
Materials for ceramic and metal substrates
However, a similar effect was recognized in terms of purity.

Here, the shape of the hot pressing mold according to the present invention may be a cylindrical shape, a rectangular tube shape, or a free-form shape having various curved shapes, depending on the shape of the sintered body to be finally obtained. Can also be applied.

The C / C composite material used in the present invention is manufactured by the following typical method. That is, first
A tubular structure is assembled using carbon fibers starting from synthetic polymer materials such as polyacrylonitrile, rayon, and phenol resin, or carbon fibers starting from petroleum pitch, coal pitch, or the like. Next, after impregnating such a structure with a carbonic resin such as a phenol resin or a furan resin or pitches and curing the structure, 700 ° C
By firing and carbonizing at the above heating temperature, a C / C composite material as a final product can be obtained. In order to obtain a more dense and high-strength C / C composite material, it is appropriate to repeat the above resin impregnation-curing-carbonization process a required number of times.

As another method for obtaining such a C / C composite material, instead of the method of resin impregnation as described above, pyrolytic carbon is uniformly deposited in the carbon fiber structure by a CVD process. There is also a way to do it.

[0014]

According to the present invention, the content of each of iron, aluminum, nickel, chromium and vanadium contained in the C / C composite material, which is the outer cylinder of the hot pressing mold, is set to a certain value or less. Contamination during sintering of the electrode sputtering target for semiconductors is prevented. Then, this suppresses the generation of the interface state of the thin film based on the obtained sputtering target, and as a result, acts to eliminate the cause of junction leakage and the like. Similarly, by setting the content of the alkali metal contained in the C / C composite material, which is the outer cylinder of the hot pressing mold, to a certain value or less, the MOS interface characteristics of the thin film based on the obtained sputtering target. It acts to prevent the deterioration of. It is considered that the same effect can be obtained for the ceramic target material.

Further, according to the present invention, the total amount of impurities in the C / C composite material, which is the outer cylinder of the hot pressing mold, is set to a certain value or less, so that the elements gasified from the hot pressing mold can be changed. Based effects can be minimized.

[0016]

EXAMPLES Next, examples of the present invention will be described. Figure 1
It is a schematic sectional drawing of the hot press apparatus in which the mold for hot pressing which concerns on this invention is used. In FIG. 1, reference numeral 1 denotes a hot press mold outer cylinder made of a C / C composite material,
Reference numeral 2 denotes an inner cylinder of the hot pressing mold, both of which are in a fitted state. Reference numeral 3 denotes a heat insulating material having an appropriate material and shape, which is configured to surround the hot press mold outer cylinder 1 and the hot press mold inner cylinder 2. Reference numeral 4 denotes a required substance to be sintered, which is loaded in the hot press mold inner cylinder 2. A set of a punch 5, a push rod 6 and a press base 7 is provided one above and one below the inner cylinder 2 for hot pressing in which the substance to be sintered 4 is charged. The required pressure is applied to the binder 4. Further, an induction heating coil 8 is provided on the outer periphery of the heat insulating material 3, and the material to be sintered 4 is
Used for heating. For comparison with the case of the embodiment of the present invention, the case not according to the embodiment of the present invention is given as a comparative example.

[0017]

[Example 1]: The following results were obtained when ash analysis by emission spectroscopy was performed on a C / C composite material that had been deashed by heating in a chlorine gas atmosphere. That is, the total content of impurities is 50 ppm; the content of iron is 3.1 pp
m; aluminum content 4.1 ppm; nickel content 2.5 ppm; chromium content 1.1 pp
m; Panadium content was 0.9 ppm; Sodium content was 1.0 ppm; and Potassium content was 0.7 ppm.

Using such a C / C composite material as the outer cylinder of the mold, and using the one processed from high-purity graphite material as the inner cylinder, a mold for hot press having an outer diameter of Φ350 mm × inner diameter of Φ200 × height of 200 mm was prepared. . Then, the following molybdenum silicide (MoSi
2) 14.0 Kg of powder was loaded. That is, the content of iron, aluminum, nickel, chromium, vanadium, sodium, and potassium as metal impurities is 0.03 ppm or less, and molybdenum silicide (MoSi) is used.
2) 14.0 kg of powder was charged. This is put in a hot press furnace and 300 kg / g under an argon gas atmosphere.
While pressurizing to cm2, the temperature was kept at 1320 ° C for 2 hours. Then, by cooling with an appropriate base, a target disk was obtained as a final product. A part of the target disk thus obtained was taken out as a sample piece, and when the impurity content was measured for this, the contents of iron, aluminum, nickel, chromium, vanadium, sodium, and potassium were: All were 0.03 ppm or less.

[0019]

[Example 2]: The results of the required ash analysis of the C / C composite material which had been subjected to a predetermined thermal deashing treatment in a vacuum heating furnace were as follows. That is, the total content of impurities is 470.
ppm; iron content as an individual impurity is 50.5 pp
m; aluminum content 61.2 ppm; chromium content 2.7 ppm; nickel content 8.1 pp
m; vanadium content was 3.8 ppm; sodium content was 10.0 ppm; and potassium content was 4.5 ppm. Using a mold for hot pressing having such a C / C composite material as an outer cylinder, the contents of iron, nickel, chromium, vanadium, sodium and potassium as metal impurities are the same as in the case of the first embodiment. In each case, silicon carbide (SiC) powder of 0.07 ppm or less was charged to the hot-breathing mold in an amount of 6.5 Kg. This was placed in a hot press furnace and kept at a temperature of 2000 ° C. for 1 hour while pressurizing to 350 Kg / cm 2 under an argon gas atmosphere. Thereafter, the target disc was obtained as a final product by cooling at an appropriate pace. A part of the target disk thus obtained was taken out as a sample piece, and the content of impurities was measured for it. The contents of iron, nickel, chromium, vanadium, sodium, and potassium were all It was 0.09 ppm or less.

[0020]

[Comparative Example 1]: Total content of impurities is 960 ppm; Content of iron as individual impurities is 93.3 ppm; Content of aluminum is 95.2 ppm; Content of nickel is 2.
5 rpm; chromium content 8.8 ppm; vanadium content 17.1 ppm; sodium content 4
1.0 ppm; and the content of potassium is 10.9 p
Using pm C / C composite material as an outer cylinder, outer diameter Φ350
A hot pressing mold of mm × inner diameter Φ200 mm × height 200 mm was prepared. Following this, iron, aluminum, nickel, chromium, vanadium as metal impurities,
Both sodium and potassium content 0.03
14.0 Kg of molybdenum silicide (MoSi2) powder of less than ppm was charged to the hot pressing mold. Then, hot pressing was performed under the same conditions as in Example 1 described above to produce a target disk as a final product. The result of measuring the impurity content of the sample piece taken out from the target disk thus produced was as follows. That is, the content of iron as an individual impurity is 9.0 ppm; the content of aluminum is 4.4 ppm; the content of nickel is 2.2 pp.
m; chromium content 3.0 ppm; vanadium content 1.9 ppm; sodium content 7.0 pr
m; and the content of potassium was 1.1 ppm.

[0021]

[Comparative Example 2]: Using the same hot-pressing mold as in Comparative Example 1 described above, the content of iron, aluminum, nickel, chromium, vanadium, potassium and potassium as metal impurities is 0.07 ppm. The following silicon carbide (SiC) powder was charged in an amount of 6.5 Kg. On the other hand, hot pressing was performed under the same conditions as in Example 2 to produce a target disk as a final product. Then, the sample pieces taken out from the target disk thus obtained were measured for a predetermined impurity content, and the results were as follows. That is, the content of iron as an individual impurity is 7.9 ppm; the content of aluminum is 4.0 ppm; the content of nickel is 2.1 ppm; the content of chromium is 3.2 ppm; the content of vanadium is 2.5 ppm. The sodium content is 8.0 ppm; and the potassium content is 2.1 pp
It was m.

[0022]

As described above, by hot-pressing high-purity metal powder or ceramic powder using the hot-pressing mold of the present invention, contamination due to thermal diffusion is prevented, and high-purity and homogeneous baking is performed. The bonded body can be manufactured with a good yield. In particular, the use of the hot-pressing mold according to the present invention makes it possible to remove the influence of contamination by a specific impurity when producing a sputtering target material made of metal or ceramics, so It is extremely useful for obtaining thin films having excellent physical properties and electronic properties.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a hot press machine in which a hot press mold according to the present invention is used.

[Explanation of symbols]

1 --- C / C composite material hot press mold outer cylinder, 2 --- hot press mold inner cylinder, 3--heat insulating material, 4--sintered material, 5--punch, 6-push rod , 7 --- Stand, 8 --- Induction heating coil.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B30B 11/02 F C04B 35/645 F27B 17/00 F

Claims (1)

[Claims] 1. A cylindrical hot pressing mold which constitutes a furnace core of a device for hot pressing metal powder or ceramic powder, wherein the outer cylinder of the mold is made of carbon-bonded carbon fiber composite material. The total content of impurities other than carbon as the main component of the carbon-bonded carbon fiber composite material is 900 p.
pm or less; the content of sodium among the impurities 25
ppm or less; potassium content is 25 ppm or less; iron content is 80 ppm or less; aluminum content is 90
ppm or less; nickel content is 15 ppm or less; chromium content is 10 ppm or less; vanadium content is 3
0 ppm or less; A mold for hot pressing.