AVS 45th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Monday Sessions
       Session MM+VT-MoA

Paper MM+VT-MoA4
A Dual Sensor Vacuum Gauge: Advanced Micromachined Thin Film Pirani Sensor Combined with a Piezoresistive Sensor

Monday, November 2, 1998, 3:00 pm, Room 324/325

Session: Vacuum MEMS and Microanalysis
Presenter: D.H. Baker, Teledyne Hastings Instruments
Authors: D.H. Baker, Teledyne Hastings Instruments
R.A. Outlaw, Teledyne Hastings Instruments
D. Rosenblatt, Rosenblatt Associates
Correspondent: Click to Email
A new dual sensor vacuum gauge which employs an advanced thin film micromachined Pirani sensor combined with a B ion implanted Si piezoresistive sensor has been developed. The two sensors are mounted on a single header and welded into a small volume (2 cc), 316 stainless steel envelope which can withstand an over pressure of 1000 psi. The instrument is UHV compatible and can detect pressure from 1000 Torr down to less than 1x10@super -5@ Torr. It is shock resistant, altitude insensitive, and bakeable to 250°C. The gas composition insensitive piezoresistive sensor permits cross over to the gas composition sensitive Pirani, thus establishing the calibration of the Pirani in the gas environment at the crossover pressure. Design criteria leading to the present sensor configurations are discussed. In particular, material selection and heat transfer solutions for the fully contiguous membrane and the various suspended geometric designs are presented. Membrane stress levels characteristic of each design are also discussed. Finally, thermal and electronic noise limitations are considered to establish the ultimate sensitivity of the instrument.