MICRO: Green Manufacturing

Sam Q. Gu, Susan Allen, Chris Bowker, and Bruce Whitefield, LSI Logic; and Han Xu and Richard L. Bersin, Ulvac Technologies on implantation through resist-coated silicon wafers is used to control doping levels in integrated-circuit fabrication. However, high-current or high-energy implant ions can sputter silicon or silicon dioxide (SiO ) from the wafer substrate and deposit residues on top of the resist. In addition, implant species can penetrate into the resist, causing the formation of a resist crust and other residues. Therefore, following ion implantation, the resist should be removed, leaving the wafer surface residue-free. Typically, oxygen plasma and a piranha wet-clean application, a mixture of sulfuric acid (H ) with either hydrogen peroxide (H ), are used to remove the resist. However, while oxygen plasma can ash the carbon and hydrogen components in the resist, it does not remove all inorganic residues from the wafer surface. Piranha wet cleans, which have conventionally been used to ensure the total removal of organic residues from the wafer surface, can remove some carbon and hydrogen, but they do not strip inorganic residues effectively. Moreover, the piranha process is costly and hazardous. The veil of inorganic residue (implant species, silicon, SiO , and additives in the resist) often remaining on the wafer after oxygen ashing and a piranha clean would affect subsequent implant steps and must be stripped prior to further wafer processing. While additional wet chemistries such as SC-1 (NH O) or diluted hydrofluoric acid (HF) can be used to remove these residues, they are costly. This article focuses on a program initiated at LSI Logic (Gresham, OR) to evaluate an alternate technology combining dry plasma processing and simple DI-water rinses in a conventional spin rinse-dryer. The technology combines an O reactive ion etch (RIE) process to remove resist crust and the addition