Reactions of halogens with surfaces stimulated by VUV light

Abstract

Reactions of halogens (Cl2,XeF2) with metals (Cu) and semiconductors (Si, GaAs) are investigated. The mainfocus is put on light induced reactions, stimulated by synchrotron radiation in thespectral range from 200 to 50 nm, in comparison with the dark reaction. Growth ofreaction products on the surface and the desorption of volatile compounds arestudied. A set-up with a quartz microbalance was adopted to determine reactionrates in situ. The rates are very sensitive to sample preparation. In the systemCu/Cl2, oxygen was found to especially slow down the reaction and much higher reaction ratesthan reported previously were observed for pure samples. Measurements with masks showthe possibility of using desorption (also called light induced dry etching) to microstructurematerials. Analysis of the irradiations with different wavelengths reveals a high spectraldependence of the reactions, which can therefore be controlled. The efficiency ofthe light induced non-selective reaction follows the gas phase absorption of theetching gases, whereas selective reactions, which are used to structure the materials,are induced in adsorbed halogens at different wavelengths. High efficiencies ofsingle-photon events, due to chain reactions, with multiplication factors of the order of105, are observed. The resulting pit size has to be contrasted with the intended spatialresolution.