Electricity: motive power systems – Braking – Automatic and/or with time-delay means
Patent
1986-03-27
1988-03-01
Dobeck, Benjamin
Electricity: motive power systems
Braking
Automatic and/or with time-delay means
318341, 318481, 318599, 318645, H02P 516
Patent
active
047288698
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.
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IBM Tech. Disclosure Bulletin, vol. 18, No. 7, Dec. 75, p. 2082 "Controlling (Reaction) Pressure in CUD Tools", by R. F. Chapello.
Elliott Gary C.
Johnson Noel H.
Anicon, Inc.
Dobeck Benjamin
Walker William B.
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