Diffusion furnace
US4347431A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Jul 25, 1980 |
| Grant date | Aug 31, 1982 |
| Priority date | — |
| Expiry date | Jul 25, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B3/64
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A diffusion furnace (11) includes a typical process tube (12) and an outer envelope (26) which forms an annular chamber (37) with the process tube. A heating element (29) of high purity graphite substantially surrounds the process tube within the chamber (37). Inner surfaces of the chamber (37) are made of materials such as, for example, silicon, pyrolytic graphite or quartz. Such materials are essentially free of harmful impurity elements such as iron, nickel, copper calcium or gold, which have an energy level about halfway between the valence and the conduction band of a semiconductor material to be processed within the process tube. A nonoxidizing gas within the heater chamber protects the graphite elements therein from oxidation. A small gas flow within the chamber (37) is preferred to purge such harmful impurity elements as may penetrate into the chamber during the operation of the furnace.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.