Characterization of high density CH4/H2/Ar plasmas for compound semiconductor etching

Abstract

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 discussed.

Plasma Polymerization of Thin Films: Correlations between Plasma Chemistry and Thin Film Character

“…Quadrupole Mass Spectrometer. The quadrupole mass spectrometer (QMS) has been described previously . The plasma ion flux mass distributions are measured with a 1−1000 amu Extranuclear ELQ400 quadrupole mass spectrometer.…”

Inductively coupled plasma etching of HgCdTe using a CH4-based mixture

“…7), in agreement with the results of Eddy. 29 The ion flux and energy remain nearly constant, when CH 4 concentration varies and all other plasma parameters are kept constant. The HgCdTe etch rate as a function of CH 4 concentration in a CH 4 -H 2 mixture is shown in Fig.…”

A langmuir probe investigation of electron cyclotron resonance argon-hydrogen plasmas

“…Normally, at low pressures, Ͻ10 mTorr, the ion density and electron density are strongly influenced by pressure. 11,17,18 The more particles there are in a chamber, the more ionization occurs. At higher pressures, Ͼ50 mtorr, collisions can begin to dominate and reduce ion and electron density.…”

“…13,16 The effects of changes in hydrogen on the plasma, especially those used to process II-VI materials, are not nearly as well understood. 9,17,18 Several plasmas were struck with different ratios of argon and hydrogen in order to investigate the impact of such changes on the plasmas. A summary of the Langmuir-derived values for ion density and ion current are presented in Fig.…”