Investigation of the kinetic mechanism for the ionhyphen;assisted etching of GaAs in Cl2using a modulated ion beam

摘要

There is increasing technological interest in using Cl2and Clhyphen;containing compounds in the dry plasma etching of IIIndash;V semiconductors. This paper presents a study of the ionhyphen;assisted etching of GaAs by Cl2using a modulated ion beam technique to gain insight into the kinetic mechanism of this process. The etching rate increases with increasing ion energy (0.3ndash;3 kV) and depends linearly on ion flux (1.0ndash;10.0times;1014ions cm2thinsp;s). The etching rate increases with increasing Cl2pressure up to a saturation limit near 2times;10minus;6Torr. This saturation limit is independent of the ion flux coincident on the surface within the range studied. The ionhyphen;enhanced etching rate decreases with increasing sample temperature over the range 300ndash;500 K. Major etch products are AsCl3and GaCl2(and possibly GaCl), and the time dependence of the increase in these mass spectrometer signals following the initiation of the ion pulse is consistent with all of the products having a most probable translational energy of sim;0.14 eV. There is an additional delay in the appearance of the AsCl3signal which roughly corresponds to a first order reaction with an associated time constant of 1.1 ms. One possible kinetic mechanism for the ionhyphen;enhanced etching is proposed which involves the surface reactions of Ga and AsCl with adsorbed chlorine. In this model, the sim;1 ms delay in the appearance of the AsCl3is attributed to the lifetime of potential energy excitation caused by the ion.