AVS 50th International Symposium
    Manufacturing Science and Technology Monday Sessions
       Session MS-MoM

Paper MS-MoM8
Hydrogen Pressure Dependence of Trench Corner Rounding during Hydrogen Annealing

Monday, November 3, 2003, 10:40 am, Room 309

Session: Process and Equipment Integration and Development
Presenter: H. Kuribayashi, Fuji Electric Corporate Research and Development, Ltd., Japan
Authors: H. Kuribayashi, Fuji Electric Corporate Research and Development, Ltd., Japan
R. Shimizu, Fuji Electric Corporate Research and Development, Ltd., Japan
K. Sudoh, Osaka University, Japan
H. Iwasaki, Osaka University, Japan
Correspondent: Click to Email
Hydrogen annealing has become increasingly important for silicon device processes. Especially for trench gate MOSFETs, both trench corner rounding and sidewall surface smoothing are quite essential for the ruggedness and reliability of gate oxide. Though the evolution of crystal shape through surface self-diffusion during heating in vacuum has been extensively investigated, it has not been sufficiently studied in specific ambients, which are applicable to semiconductor processes. At the preceding meeting we studied shape transformation of silicon trenches with sidewall surface of (110) and (-110) during annealing in hydrogen ambient at 1000°C, and showed that the observed shape transformation can be simulated well with Mullin's continuum surface model@footnote 1@ with surface self-diffusion. In this work, to study the roll of hydrogen gas on the Si surface self-diffusion in more detail, we investigated both the hydrogen pressure dependence and the temperature dependence of the trench corner rounding for wider range of pressure (10-760Torr) and temperature (1000-1100°C), respectively. We found a remarkable effect of hydrogen on trench corner rounding. The curvature of a trench corner for a certain annealing time increases linearly with increasing hydrogen pressure. The diffusion coefficient at 1000°C deduced by the Mullin's formula decreased from 2x10@super 5@nm@super 2@/sec at 100Torr to 3x10@super 3@nm@super 2@/sec at 500Torr, which are much smaller than the one in vacuum@footnote 2@ by three to five orders of magnitude. The diffusion coefficients did not follow the Arrhenius relations for 1000-1100°C in the higher-pressure region above 100Torr, suggesting that more than one rate-limiting processes are involved in the temperature range. @FootnoteText@ @footnote 1@W.W.Mullins, J.Appl.Phys.28, 333(1957).@footnote 2@Y.-N. Yang, Elain S. Fu, and Ellen D. Williams, Surf. Sci. 356,101(1996) .