JPS63186865A - Crucible for vapor deposition - Google Patents

Abstract

PURPOSE:To improve the durability of a crucible for molten Al, etc., by coating a soln. of polycarbosilane to a graphite crucible having specific porosity as said crucible and drying the coating, then heating the crucible in an inert atmosphere, thereby thermally decomposing the polycarbosilane and converting the same to SiC. CONSTITUTION:The crucible for molten Al, Ag, etc., to be used at the time of vapor deposition of said metals is produced of the graphite which is so adjusted that the ratio to be occupied by 50-6,000Angstrom pores among the pore size measured by a mercury penetration method is >=25% and the porosity thereof is <=15%. The 10-20% soln. of the polycarbosilane contg. n-hexane as a solvent is coated and impregnated on and in such graphite crucible and is then dried at 200-350 deg.C in air; following which the crucible is heated at 800-1,500 deg.C to thermally decompose the polycarbosilane and to form the SiC film. Since said film has extremely low affinity to the molten Al, etc., the creeping up of the molten Al, etc., onto the top end face of the crucible or the deposition of said metals onto the top end face and sagging thereof to the outer side face to erode the graphite crucible are obviated and the graphite crucible which withstands long-term use is obtd.

Description

[Detailed Description of the Invention] (Industrial Applicability) The present invention evaporates molten metal such as aluminum or silver at high temperature and under high vacuum, and deposits these metals on the surface of a material such as a film or sheet. This invention relates to a crucible used in so-called metal vapor deposition (hereinafter referred to as a vapor deposition crucible).

(Prior art and its problems) For example, in the case of aluminum vapor deposition, a vapor deposition crucible that can achieve such a purpose is 1200'C to 1500'C.
Since the material must be able to withstand use under high vacuum conditions of -10-' to 10-' mm Hg at high temperatures of -10-' to 10-' mm Hg, it is usually graphite that has undergone various treatments, such as impregnation with aluminum oxide. materials were used. When this graphite vapor deposition crucible is used repeatedly, its interior, especially the bottom side, becomes corroded, and eventually holes are formed, making it impossible to use.

Therefore, in many cases, molten aluminum creeps up to the h-end or deposits on the upper end surface during its use, and this drips down to the outer surface of the deposition crucible, where a chemical reaction between the molten aluminum and graphite occurs. As a result, this portion becomes eroded, the wall thickness of the side wall decreases, or cracks occur, eventually making it impossible to use.

Therefore, the hanging of aluminum on the side of the deposition crucible is caused by the deposition crucible as described above.

Not only does this shorten the lifespan (number of uses) of heat insulating materials such as carbon fibers and increase their cost, but if the crucible for deposition cracks, high-temperature molten aluminum flows out, resulting in expensive vacuum deposition. Safety 1- is not preferable because the equipment may be contaminated or, if this is significant, the equipment may be damaged.

If the vapor deposition crucible is damaged, the film or sheet as a product will not be completely vapor-deposited, and will lose its commercial value, resulting in a large amount of loss.

(Means and effects for solving the problems) As a result of long-term research in order to solve the above problems, the present inventors have devised a crucible for vapor deposition that is more durable than conventional crucibles. The present invention has now been completed.

That is, the present invention provides polycarbosila Hn dissolved in a solvent in part or all of a vapor deposition crucible made of graphite material whose porosity is adjusted to 15% or less and whose proportion is 25% or more as determined by mercury porosimetry. is impregnated, dried in the air at 200 to 350°C, and then heated at 800 to 1500°C in an inert atmosphere to form silicon carbide by thermal decomposition of the polycarbosilane coated on the surface of the substrate or in the voids. Forming a film (hereinafter referred to as SiC
The aim is to increase the number of times the metal can be used by preventing creeping of molten metal or corrosion of the crucible.

According to the present inventors, if the surface layer of the crucible for vapor deposition, the voids, or the base material itself is made of SiC, the compatibility with molten aluminum is extremely low, so that molten aluminum will overcome this and proceed to the outside. It has been found that the cases where the crucible cannot be removed and is returned to its original crucible and hangs down on the outer surface are almost completely eliminated. On the other hand, conventional SiC conversion methods include (1) conversion method and (2) SiC conversion method.
There is also a C-CVD coating method. The conditions for its production were extremely difficult and required a great deal of experience and equipment.

On the other hand, the polycarbosilane in the present invention has 20
Air drying at 0 to 350°C, 800 to 15 Hn CH4+) (2) can be easily converted to SiC, and can be effectively treated by setting the solution concentration to 10 to 20%.

When the concentration is less than 10%, the efficiency is poor because only a small amount of SiC is produced, and when the concentration of the solution exceeds 20%, the viscosity becomes high, causing the problem of uneven coating or impregnation. When the solution concentration is 10 to 20%, the coating on the surface layer of the crucible or impregnation into the bore part is performed smoothly, and a crucible for vapor deposition with excellent durability can be obtained with one to several treatments. We found that concentration control is a very important point.

In addition, by adjusting the proportion of pores in the graphite material of the crucible for vapor deposition to 25% or more and 15% or less using the mercury intrusion method, the polycarbosilane solution can be applied and impregnated efficiently. This results in a dramatic effect on durability.

If the porosity is less than 25% or the porosity is more than 15%, repeated treatments of the polycarbosilane solution are required, and voids remain even after conversion to SiC, making it impossible to expect great durability. It is.

(Example) Examples of the present invention will be described below.

Example 1 A 15% solution of polycarbosilane dissolved in n-hexane was placed in a deposition crucible with a porosity of 7% and a porosity of 50 Å to 6000 A accounting for 65% of the pore diameter determined by mercury porosimetry. After impregnating and drying at 250°C in air 1
When it was heat-treated to 200°C and subjected to a practical test for aluminum vapor deposition, after an average of 60 uses, the imitation of the outer surface was slight, or the imitation of the lower part of the inner surface progressed and the wall became thick or thin, so use was discontinued.

Example: Of the pore diameters obtained by mercury intrusion method, the proportion of pores of 50 Å to 6000 A accounts for 50%, and the porosity is 11%.
Impregnated with a 18% solution of polycarbosilane dissolved in n-hexane, and to further increase the anti-climb effect, after applying the same solution to the upper end, the pot was heated at 250°C in air.
It was dried at 1,200'C and subjected to a practical test for aluminum vapor deposition.The average number of times it was used was 58, and there was almost no imitation of the outer surface, but the imitation of the lower part of the inner surface was advanced, so it was graded as medium II. .

(Comparative example) A crucible obtained by impregnating a crucible with aluminum oxide was subjected to a practical test for aluminum evaporation. After using it 25 times, its outer surface imitated aluminum and became unusable.

(Effects of the Invention) As described above, the present invention can easily convert into SiC by coating or impregnating a polycarbosilane solution on a vapor deposition crucible made of graphite material with adjusted pore size and porosity. It is highly effective and extremely useful in improving the durability of crucibles for aluminum evaporation.

that's all

Claims (1)

[Claims] Of the pore diameter measured by mercury intrusion method, 50 Å to 60
Polycarbosilane, which is an organosilicon polymer, is coated or impregnated on part or all of a vapor deposition crucible made of graphite material in which the proportion of 00 Å pores is 25% or more and the porosity is 15% or less. . A vapor deposition crucible, characterized in that a silicon carbide film is formed from the polycarbosilane.