Y. Feurprier et al., INFLUENCE OF THE GAS-MIXTURE ON THE REACTIVE ION ETCHING OF INP IN CH4-H-2 PLASMAS, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 15(5), 1997, pp. 1733-1740
The influence of the CH4-H-2 mixture composition on the etching proces
s of InP is investigated by means of plasma diagnostics (optical emiss
ion spectroscopy and mass spectrometry) and quasi in situ x-ray photoe
lectron spectroscopy (XPS) surface analysis. Increasing the mixture co
mposition in methane increases the InP etch rate. For example, it rise
s from 230 to 380 Angstrom/min when increasing the percentage in CH4 f
rom 2.5% to 75%. In pure methane discharge, at a pressure of 50 mTorr,
amorphous carbon is deposited on InP. Quasi in situ XPS reveals major
changes in the surface chemistry. In particular P depletion decreases
and the mean surface stoichiometry improves as the percentage of meth
ane increases. The mass spectrometry PH3+ signal (m/e=34 amu) correspo
nding to PH3 molecules and the In emission line (lambda=451.1 nm), wh
ich are, respectively, characteristic signals of the individual remova
l rate of In and P, and the concentration of CH3 radicals in the plasm
a as measured by the threshold ionization technique display good agree
ment with the etch rate and surface chemical modifications. These resu
lts confirm that the etching mechanism of InP is controlled by the etc
hing mechanism of In, and that the latter is strongly correlated with
the concentration of methane in the mixture. Variable photoelectron em
ission angle measurements are performed to determine precisely the loc
ation of the species in the damaged layer. A model for the representat
ion of the surface in the process of etching is then proposed. (C) 199
7 American Vacuum Society. [S0734-211X(97)02205-1].