SIMPLE CALIBRATED GAS FEED SYSTEM

Constant calibrated gas flow is needed in vacuum processes such as plasma etching and sputtering. It is shown that capillary tubes combined with a simple pressure regulator can give satisfactory results. Typical calibrations for different capillary lengths, diameters, and for different gas types (A, N 2, H2, He, CH4, CCl2F2, CHClF2) are given. Agreement with viscous flow theory is good, and over a 100:1 range in flowrate the resettability and variability in flowrate varies from ±2% to ±20%.