Reactive Etching Of Semiconductor Surfaces By Laser-Generated Free Radicals

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Abstract
Reactive etching at silicon and silicon-oxide surfaces is customarily carried out in a fluorocarbon plasma. Under such conditions, a large variety of reactive species is generated, making it extremely difficult to elucidate details of the etching mechanism; in addition, the charged species present in the plasma frequently produce undesirable radiation damage in the finished devices. We have found that dissociation of the parent fluorocarbons by multiple-infrared-photon excitation produces reactive neutral fragments which are capable of etching these surfaces. Etch gases such as CF3Br, CF2HC1, CF300CF3, and SF, may be used with poly-Si, Si02, Si3 Nd' and other substrates; SEM, ESCA, and Auger diagnostics are employed to characterize the reactions occurring at the surface. From these experiments we hope to develop a quantitative model for the reactive etching process. Possible commercial advantages of the laser-etching technique include reduction or elimination of radiation damage, increased etching rates, and improved Si02/Si specificity.

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