CHARACTERIZATION OF HIGH DENSITY CH4/H2/AR PLASMAS FOR COMPOUND SEMICONDUCTOR ETCHING

High density plasmas generated using gas mixtures of methane, hydrogen, and argon are characterized using mass spectrometry, optical emission spectroscopy, and three dimensional Langmuir probing. Such plasmas are commonly used to etch compound semiconductors. In this work we examine the chemical and electrical properties of the flux to the region where substrates are placed during processing. The dominant species in the flux are identified as H, H+, CH3, CH3+, Ar, and ArH+. Plasma parameters in the source region include electron temperatures of 4–9 eV, plasma densities of 1–5×1011 cm−3, and plasma potentials of 24–44 V as process conditions are varied. These parameters are considerably reduced in the process region of the plasma to electron temperatures of 2–6 eV, plasma densities of 1×109 to 2.5×1010 cm−3, and plasma potentials of 3–14 V. Mass and optical emission spectral data are correlated to Langmuir probe results and the effects of varying process conditions on plasma properties are presented and di...