AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP12
Shape Transformation of Silicon Trenches during Hydrogen Annealing

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: H. Kuribayashi, Fuji Electric Corporate Research and Development, Ltd., Japan
Authors: H. Kuribayashi, Fuji Electric Corporate Research and Development, Ltd., Japan
R. Hiruta, 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
In trench gate MOSFETs, trench corner rounding, which is caused by surface self-diffusion during heat treatments, is significant for the gate oxide reliability. Though the evolution of a crystal shape through surface self-diffusion during heating in vacuum has been extensively investigated, it has not been sufficiently studied in specific ambient, which is applicable to semiconductor process. In this work, we have studied the shape transformations of silicon trenches through surface self-diffusion during annealing in hydrogen ambient. The trench stripes on Si(001) with a depth of 3µm were fabricated by RIE technique with HBr contained gas plasma, where the trench sidewall surface orientation was chosen to be (110) and (-110). Then the samples were annealed at 1000°C in hydrogen ambient at various hydrogen pressures. The cross-sectional profiles of the trenches were observed by SEM after cleaving the substrates along the trench stripes. The observed time evolution of trench shapes was well reproduced by numerical simulation based on Mullins' continuum theory.@footnote 1@ Thus we confirmed that the evolution of the trench-shape was due to Si surface self-diffusion. From comparison between the time scales in the experiment and the simulation, the diffusion coefficient was estimated to be about 2x10@super 6@nm@super 2@/sec at 5.3kPa, which is smaller than that at vacuum ambient.@footnote 2@ It was found that the rate of shape transformation decreased with increasing hydrogen pressure, showing strong pressure dependence of the diffusion coefficient. In the symposium, we are going to discuss the dependence of silicon surface on hydrogen pressure in detail. In addition, the behavior of atomic steps on the trench sidewall surfaces, which was observed by AFM, will be also discussed. @FootnoteText@ @footnote 1@W.W.Mullins, J.Appl.Phys.28,333(1957) @footnote 2@Yang et al., Surf.Sci.356,101(1996).