Document Type

Thesis

Date of Award

8-31-1990

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

William N. Carr

Second Advisor

Durgamadhab Misra

Third Advisor

N. M. Ravindra

Abstract

A new family of microengineered vacuum ionization gauges of an approximate volume of 200µ3 has been designed. These devices can he fabricated using existing semiconductor processing capabilities. The focus of this thesis is to scale down the current state-of-the-art for ionization sensors to micron dimensions. These gauges can be manufactured economically and potentially will be integrated with more complex structures and circuitry. In these devices an active ionization volume of micron dimensions is used for launching ions in a trajectory towards a collection electrode. Ionization of gas species is accomplished by an electron flux of sufficient energy. Analysis of electron and ion ballistics was carried out using SIMION, an interactive workstation based simulator. Two different ionization processes have been simulated. The first one is called avalanche ionization in which a B field is incorporated into the device. In the second case, ionization is accomplished using field emission sources of electrons. The collection electrode is positioned in planer structures for high efficiency collection of ions of interest. A family of geometries are simulated and optimized for compatibility with semiconductor processing and operational efficiency: Devices based on 3 and 4 photolithographic masking levels are described in this thesis. The maximum pressure ambient for this family of devices is limited by sputtering of electrodes. The minimum detectable pressure level of 10-7torr is determined by electrometer sensitivities and device current leakage.

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