Deuterium post metal annealing of MOSFETs for improved hot carrier reliability

SIMS analysis results prove that at typical anneal temperatures (400-450 C), deuterium diffuses rapidly through the interlevel oxides and accumulates at Si/SiO₂ interface. The improved hot electron reliability phenomena can be understood as a kinetic isotope effect where chemical reaction rates involving heavier isotopes are reduced, and consequently under hot electron stress, bonds to deuterium are broken much slower than bonds to protium (H). However, the static chemical bonding is evidently the same for both hydrogen and deuterium since identical transistor function is measured after hydrogen and deuterium treatment prior to hot electron dynamics and resultant damage. Therefore, it is suggested that deuterium and hydrogen post metal anneal processes are compatible with each other in semiconductor manufacturing. Recent hot electron stress data taken using a development version of Lucent Technologies 0.35 μm 3.3 V CMOS technology is presented as a confirmation of the original results. Transistor speed versus reliability trade-off in CMOS device design is also discussed in light of the findings of this study.