According to the International Technology Roadmap for Semiconductors, the backside particle requirement for optical lithography is < 94 particles per 200 mm wafer for 0.18 μm technology, and < 63 particles for 0.13 μm geometry for particles > 0.2 μm. Single-wafer cleaning processes developed by Semitool Inc. (Kalispell, Mont.) have been shown to effectively remove backside particles for copper removal and pre-lithography cleans. Results from independent experiments performed at Semitool and IMEC (Heverlee, Belgium)rndemonstrated Cu removal to below detection limits ( < 1E11 atoms/cm~2 Cu) from the wafer backside, bevel and opposite side edge exclusion zone. In addition, an O_3/hydrofluoric mixture was developed for backside particle removal before photolithography.
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