Closed loop method and apparatus for preventing exhausted reactant gas from mixing with ambient air and enhancing repeatability of reaction gas results on wafers
US5118286A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 17, 1991 |
| Grant date | Jun 2, 1992 |
| Priority date | — |
| Expiry date | Jan 17, 2011 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF27D17/20
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
Mixing of spent reactant gases with ambient air inside a semiconductor wafer fabrication facility is avoided and consequently corrosion of a scavenger box in a wafer fabrication facility is avoided. Repeatability of reaction gas results on wafers in a process tube is improved by maintaining precisely constant pressure in the wafer processing tube, which is operated close to ambient atmospheric pressure. This is accomplished by positioning an exhaust tube downstream from the wafers in the processing tube at a location that results in a uniform, repeatable reaction gas flow pattern between the wafers. Pressures at or near that point are measured by a differential manometer referenced to ambient atmospheric pressure to produce a pressure-indicating signal. The pressure indicating signal is electronically compared with a preset constant signal representative of the desired constant pressure at the pressure measurement point to produce an error signal. The error signal is used to continuously vary the position of an exhaust valve in the exhaust tube and thereby maintain the measured pressure constant despite variations in ambient atmospheric pressure and variations in an exhaust gas scr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.