SURFACE ADSORPTION OF WF_6 ON Si AND SiO_2 IN SELECTIVE W-CVD

摘要

Surface adsorption of WF_6 on H-free Si(l00) and SiO_2 at ~100℃ was investigated using an ultraclean cold-wall LPCVD system. On the Si surface, WF_6 was adsorbed only by WF_6 exposure and the W atom concentration increased with the exposure time, while the F atom concentration was saturated, and mainly the W-Si, W-W, F-Si bonds are formed, where the F-Si bond existed also over the adsorbed W atom. By WF_6 and SiH_4 exposure, the W atom concentration was similar to that only by the WF_6 exposure until a certain concentration. Then the concentration drastically increased, which corresponded to the W nucleus formation. On the SiO_2 surface, the W and F atom concentrations were saturated at about 10~(14)cm~(-2) and only the W-O and F-Si bonds are formed, where the O and Si atoms should be from the SiO_2 substrate. The SiH_4 addition scarecely influenced the W and F atom adsorption. Based on these results, it is considered that in the case of the Si surface, the WF_6 adsorption is possible only on the Si atom on the adsorbed W atom to form a W-W bond, while in the case of the SiO_2 surface, the WF_6 adsorption is impossible because of the absence of the Si atom on the adsorbed W atom. From the above difference of the adsorption characteristics of the WF_6 on the Si and SiO_2 surfaces, the W nuclei are formed only on the Si surface.