JPS6335091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a furnace core tube for a diffusion furnace for semiconductor manufacturing.

Diffusion furnaces insert silicon wafers etc. into the furnace core tube to diffuse impurities such as B and perform oxidation treatment, but these impurities adhere to the furnace core tube, and unnecessary impurities are gradually removed. Because of the build-up, the furnace must be shut down from time to time to clean the furnace core tube. Conventional furnace core tubes have a straight body shape at the open end, and the cleaning method is to remove the furnace core tube and do it in a bath of hydrochloric acid, etc., so the cleaning method is complicated and it is difficult to clean the furnace body. There were drawbacks such as damage.

The present invention provides a structure of a furnace core tube that can carry out such cleaning by high-temperature gas treatment. It consists of a tube and a lid made of quartz glass or silicon carbide that can be fitted into the tapered portion and has an inner circumferential surface at one end that is approximately the same taper and a gas discharge hole at the other end.

When performing gas treatment in the present invention, a lid body having a gas discharge hole is fitted to the discharge side end of the furnace core tube at the tapered part to seal the furnace core tube, and cleaning is performed from the gas discharge hole of this lid body. Cleaning gas is introduced from the other end of the furnace core tube while the gas is exhausted. Embodiments of the present invention will be described below with reference to the drawings.

In the figure, 1 is a furnace core tube made of a silicon carbide sintered body, the surface of which is coated with a dense silicon carbide film. One end of this furnace core tube 1 has a narrowed inner diameter and is in spherical contact 3 with a gas introduction tube 2 made of quartz glass. The other end is sealed with a lid 4 made of the same material as the furnace core tube. A sealed state is obtained by tapering the outer circumferential surface 5 of the end of the furnace core tube to 1/10, and closely fitting the lid 4 having the inner circumferential surface 6 of the end having a taper of 1/10. The lid body 4 is provided with a gas exhaust hole 7. In this case, even if the lid body 4 is made of quartz glass, it can be similarly sealed by providing a tapered surface.

If a furnace core tube with such a structure is used and the inner wall surface is contaminated due to diffusion treatment, etc., introduce a halogen gas such as hydrochloric acid or chlorine through the gas introduction hole and heat the inside of the furnace to a temperature of 1100°C or higher, for example 1300°C. By heating, contaminants can be expelled from the gas outlet very easily. The reason why the furnace body is heated to 1100°C or higher is because the cleaning effect is low at low temperatures and cleaning takes a long time.

In addition, since the lid comes into contact with high-temperature gas, it should be tapered to take into account thermal expansion and maintain a sealed state against corrosive gas even at high temperatures, and the angle should be between 1/5 and 1/50. is necessary. This tapered contact allows for sealing even with quartz glass, which has a small thermal expansion, and sealing becomes easier if it is made of the same material as the furnace core tube. Since the temperature on the gas introduction side is relatively low, there is no need to consider thermal expansion, so conventional spherical contact or other methods are possible.

Since the furnace core tube of the present invention has such a structure, the halogen gas cleaning effect is extremely high, there is no gas leakage even at high temperatures, and there is no need to cool the furnace body or take out the furnace core tube. , the inside of the furnace core tube can be cleaned very easily.

The material of the furnace core tube is not limited to silicon carbide coated with silicon carbide, but also silicon carbide impregnated with metallic silicon or silicon nitride coated. These materials can be used.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a furnace core tube for a diffusion furnace showing an embodiment of the present invention. 1...furnace core tube, 2...gas introduction tube, 3...spherical contact,
4... Lid body, 5... Furnace tube end outer peripheral surface, 6... End inner peripheral surface, 7... Gas discharge hole.

Claims (1)

[Claims] 1. A silicon carbide furnace core tube whose outer circumferential surface on the cleaning gas discharge side has a taper of 1/5 to 1/50, and a quartz glass whose inner circumferential surface at one end that can fit into this tapered portion has approximately the same taper. A structure of a furnace core tube for a high-purity diffusion furnace, characterized by comprising a silicon carbide lid body.