WSPS: WAFER SURFACE PREPARATION SYSTEM. A NOVEL MODULAR AUTOMATED METHOD CAPABLE OF THE ULTRATRACE ANALYTICAL INSPECTION OF 300 MM SILICON WAFER SURFACES

摘要

TXRF has become a standard on-line inspection tool controlling the cleanliness of polished Si wafers in semiconductor industry. Wafer makers strive for overall metallic cleanliness < 10~(10) atoms cm~2. Overall cleanliness can be evaluated by VPD/TXRF. For a fully automated VPD preparation and scanning of 300 mm wafers, we have developed a modular system, the "Wafer Surface Preparation System" (WSPS). The WSPS has been optimized regarding the throughput, the reduction of any background contamination, and the limit of detection. Coupled with the new generation of TXRF the robotized WSPS enables ultratrace analytical inspection down to 10 atoms cm" using chemicals of ULSI quality and ultrapure water under cleanroom conditions class <10. The merits of WSPS are high reproducibility at low element concentration levels and an enhanced wafer throughput, that is synchronized with the capacity of robotized new generation TXRF. As applied to one wafer the optional ability of VPD-droplet splitting allows the simultaneous analysis with TXRF, ICP-MS, GFAAS, LDS (Laser Diode Spectrometer), IC and CE.