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This paper discusses new experimental findings critical for process integration of deuterium post-metal anneals to improve channel hot carrier reliability in manufacturing multilevel metal CMOS integrated circuits. Detailed account of the deuterium process optimization experiments varying temperature, time, and ambient is given. Specifically, the first demonstration of the large hydrogen/deuterium isotope effect for multilevel metal/dielectric MOS systems is reported. Previous accounts of the isotope effect had been limited to CMOS structures with one-level of dielectric/metal and to about a 10 fold improvement in reliability. Deuterium, instead of hydrogen is introduced via an optimized post-metal anneal process to achieve a 50-100 fold improvement in transistor channel hot carrier lifetime. The benefits of the deuterium anneal are still observed even if the post-metal anneal is followed by the final SiN cap wafer passivation process. It is concluded that the deuterium post-metal anneal process is suitable for manufacturing high performance CMOS products and fully compatible with traditional integrated circuit processes.