Characterization of high density CH4/H-2/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 spectros copy, and three dimensional Langmuir probing. Such plasmas are commonly use d to etch compound semiconductors. In this work we examine the chemical and electrical properties of the flux to the region where substrates art: plac ed during processing. The dominant species in the flux are identified as II , H+, CH3, CH3+, Ar, and ArH+. Plasma parameters in the source region inclu de electron temperatures of 4-9 eV, plasma densities of 1-5 x 10(11) cm(-3) , and plasma potentials of 24-44 V as process conditions art: varied. These parameters are considerably reduced in the process region of the plasma to electron temperatures of 2-6 eV, plasma densities of 1 x 10(9) to 2.5 x 10 (10) cm(-3), and plasma potentials of 3-14 V. Mass and optical emission spe ctral data are correlated to Langmuir probe results and the effects of vary ing process conditions on plasma properties are presented and discussed. (C ) 1999 American Vacuum Society. [S0734-2101(99)02303-9].