AVS 47th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoA

Paper PS2-MoA3
Etch Rate Enhancement and Surface Roughening during W/Poly Si Stack Gate Etching Process

Monday, October 2, 2000, 2:40 pm, Room 311

Session: Plasma Etching of Conductors
Presenter: H. Morioka, Fujitsu Limited, Japan
Authors: H. Morioka, Fujitsu Limited, Japan
M. Nakaishi, Fujitsu Limited, Japan
T. Ishida, Fujitsu Limited, Japan
Correspondent: Click to Email
W/Poly Si stack structure is one of the most promising candidates for gate electrodes of ULSI in the next generation because of its low sheet resistance and compatibility with self-aligned contact process. But most etching processes of W/Poly Si stack gate have some distinctive problems closely related to W and W etching byproduct, such as non-uniform etch rate enhancement, serious RIE-lag, and profile anomalies. We examined the catalytic effect of W and W etching byproducts on W/Poly Si stack gate etching. Our experiments were performed on a high-density plasma etcher. The chemistry was halogen-base and oxygen was used as an additional gas, which is sometimes utilized for increasing W etching selectivity to poly Si by inhibiting Si etching. An etching sample was poly Si or SiO@sub 2@ wafer on which a W chip was attached in the center. The W chip, which was the only source of W and W etching byproduct, was etched together with the sample wafer in the reaction chamber. The etch rates were measured as a function of distance from the W chip, and the surface roughness was measured by AFM. In this experiment, we found that W and W etching byproducts enhanced the etch rate of poly-Si and SiO@sub 2@, and the enhancement depended on distance from the W chip. The etch rate was maximum near the W chip. Besides, AFM observation revealed the increase of etch pits along grain boundaries on etched poly Si surface, and the increase of roughness of etched SiO@sub 2@ surface when they were etched with the W chip. These facts suggest that W etching byproducts and their fragments decomposed in the plasma are deposited on the sample surface and vary the etching characteristics.