Importance

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Abstract

Wafer surface degradation in a photoexcitation dry cleaning process, due to volatilization of surface halides that allows the exposed silicon surface to be further etched, is obviated by controlling the conditions of the process, specifically silicon wafer surface temperature, such that silicon reaction products that are formed on the surface of the wafer in the presence of the photoexcited disassociated halogen radicals do not volatilize. The silicon wafer is placed upon a low temperature chuck. When the halogen gas within the reaction chamber is irradiated with ultraviolet light, it produces disassociated halogen atoms that react with the surface of said silicon. Irradiation of the halogen gas and the surface of the silicon wafer is controlled by an optical shutter, in order to limit the amount of ultraviolet radiation that strikes and is absorbed by the wafer. The reduced temperature of the wafer prevents volatilization of a surface film containing halogen-contaminant compounds and halogen-silicon reaction products. As a consequence, further reaction of the halogen reactant radicals with silicon underlying the surface film is effectively suppressed. Thereafter, the surface film is removed from the surface of the wafer, for example by increasing its temperature in halogen free chamber at a reduced pressure, or by dissolving the film in a rinse solution, such as water.

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First Claim