| Co-Investigator(Kenkyū-buntansha) |
ONO Shoichi TOHOKU UNIVERSITY, RESEARCH INSTITUTE OF ELECTRICAL COMMUNICATION, PROFESSOR, 電気通信研究所, 教授 (00005232)
OHMI Tadahiro TOHOKU UNIVERSITY, FACULTY OF ENGINEERING, PROFESSOR, 工学部, 教授 (20016463)
MUROTA Junichi TOHOKU UNIVERSITY, RESEARCH INSTITUTE OF ELECTRICAL COMMUNICATION, ASSOCIATE PRO, 電気通信研究所, 助教授 (70182144)
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| Research Abstract |
The object of this research is to develop an anisotropic etching technology with perfect selectivity using Langmuir's adsorption layer, with focusing on selective plasma processing. Research results are summarized as follows.
(1) In ECR plasma etching, under an ultraclean condition with eliminating deoxidizing contamination onto the wafer and suppressing damages caused by ion incidence, nitrogen to addition to chlorine drastically enhances anisotropy. Direct ESCA analysis of the side wall surface of n^+-polysilicon reveals chemisorption of the N-atom forming Si-N bonds, which results in anisotropy enhancement. Exposure of the N-chemisorbed n^+-polysilicon surface to clean room air results in oxidation of the surface.
(2) The added nitrogen dependence of the etch rate is well characterized by a Langmuir-type adsorption and reaction scheme as a competitive reaction with nitrogen and chlorine. Furthermore, using the horizontal over-etch rates with and without nitrogen addition, transport and deactivation of chlorine and nitrogen radicals are evaluated.
(3) Using the same ultraclean ECR plasma system, low temperature Si selective epitaxy and inversion to selective polysilicon deposition only on SiO_2 without substrate heating was achieved by SiH_4 decomposition with a H_2 added Ar plasma. ESCA analysis shows the Si^0 adsorption on the masking SiO_2 surface, which originates from SiH_4 and suppresses SiO_2 etching, in Si selective epitaxy. Moreover, the inversion in selectivity results from the competitive contributions of chemical etching with hydrogen radicals and ion induced decomposition of SiH_4.
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