Primary pressure standard for calibration in the medium vacuum range

Abstract

Wide dynamic range silicon diaphragm vacuum sensor by electrostatic servo systemPrimary standards for gas pressure in the range from ϳ0.1 to 10 Pa ͑1 to 100 mTorr͒ have received a significant amount of attention in recent years. The interest in the calibration capability in this vacuum range is, to some degree, driven by the increasingly stringent requirements for the semiconductor processing industry. We present a new standard that is based on calculating the gas pressure required to restore a diaphragm to a null position, while the diaphragm is tilted to various, measured inclinations. With this as a basis, the calculations are relatively simple; there are no gas property dependent effects; and the system design is simple, robust, and easily automated. A formal evaluation of uncertainty for the system being developed in this facility is reviewed and compared with other primary standards. For the medium vacuum range, it is anticipated that this standard will offer numerous practical advantages relative to liquid manometers, dead weight testers, volume expansion systems, and conductance-based systems. It is intended that this technique will enable more widespread capability for the calibration, and verification of vacuum gauging in a pressure range of critical interest to many processes.