Control of oxidation on NiSix during etching and ashing processes

The oxidation on nickel silicide (NiSix) during plasma etching and oxygen ashing is investigated for stable contact resistance on NiSix. NiSix exposed by various processes is observed by X-ray photoelectron spectroscopy. The oxidation on NiSix is promoted by the fluorine that remains during etching and the oxide thickness on n+ NiSix is greater than that on p+ NiSix. The remaining fluorine after etching can be decreased by in-situ nitrogen plasma treatment during the post-etching process. Therefore, the oxidation progress with exposure to air and the difference in oxidation on NiSix between n+ and p+ can be suppressed.