Pulsewidth modulated pressure control system for chemical vapor deposition apparatus
US4728869A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 27, 1986 |
| Grant date | Mar 1, 1988 |
| Priority date | — |
| Expiry date | Mar 27, 2006 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S388/933
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A low pressure control system for chemical vapor deposition (CVD) apparatus, including a vacuum pressure chamber and an exhaust pump, is provided by a vacuum pump DC motor which is supplied power from a DC motor speed controller coupled to a DC control input signal from a pulsewidth modulation DC converter. The converter receives a single pulsewidth modulated pulse train having its percentage of modulation controlled in accordance with a DC to pulsewidth modulation controller which operates in accordance with the difference between a pair of DC input signals corresponding to the actual pressure inside the vacuum pressure chamber and a desired or set point pressure respectively. The vacuum pump motor speed and accordingly the exhaust pump is controlled with a high degree of precision, thereby providing improved coating uniformity of semiconductor wafers being fabricated by the CVD apparatus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.