Semiconducting βFeSi2 has been successfully grown on a Si (111) substrate. It has been proven that under ultrahigh vacuum conditions, the solid phase epitaxy temperature can be lowered to ∼800 K, where only the βFeSi2 phase is stabilized. The disilicide formation was monitored in situ by various surface-sensitive techniques such as low-energy electron diffraction, Auger electron spectroscopy, and ultraviolet photoelectron spectroscopy. The epitaxial relationships were ascertained by transmission electron diffraction and microscopy including high-resolution cross-sectional image. The results show the epitaxy of βFeSi2 (110) and (101) planes parallel to the Si (111) plane. The disilicide-silicon heterojunction displays an atomically abrupt interface.
Photoresist etching mechanisms in O2 abd SF6 microwave plasmas are investigated using x-ray photoelectron spectroscopy (XPS) and etch rate measurements. Experiments are performed in a microwave multipolar plasma using an electron cyclotron resonance at 2.45 GHz and independent rf biasing at 13.56 MHz. The photoresist etch rates are studied as a function of the parameters of the plasma polymer interaction. As in an O2 plasma, the etch rate in SF6 exhibits a two-step evolution with ion energy as well as a monolayerlike adsorption of atomic fluorine on photoresist. The relationship between the surface mechanisms deduced from the etch kinetics and the surface compositions analyzed by XPS is explored. The effect of reactive species concentration, intensity of ion bombardment, and surface temperature on etching and/or degradation of the photoresist is investigated. In particular, the phenomenon of resist damage, described as a graphitization of the polymer layer, is shown to appear when the mechanical effects of ion bombardment become significant with respect to the chemical effects.
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