Fundamental Investigations on Silicon Solid Phase Epitaxial Growth
Grant-in-Aid for Scientific Research (B).
|Research Institution||University of Tsukuba|
TOKUUAMA Takashi Professor, Institute of Applied Physics, 物理工学系, 教授 (40197885)
MOTOOKA Teruaki Associate Professor, Institute of Applied Physics, 物理工学系, 助教授 (50219979)
|Project Fiscal Year
1989 – 1990
Completed(Fiscal Year 1990)
|Budget Amount *help
¥6,600,000 (Direct Cost : ¥6,600,000)
Fiscal Year 1990 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1989 : ¥4,300,000 (Direct Cost : ¥4,300,000)
|Keywords||amorphous silicon / solid phase epitazial growth / structural relaxation / Raman spectrum / simulation / ion implantation / 非晶質シリコン / 固相成長 / 構造緩和 / ラマン散乱スペクトル / シミュレ-ション / イオン注入 / ラマンスペクトル|
1. Structural relaxation processes of various amorphous silicon films during low temperature annealing
Raman spectroscopy has been used to evaluate the change of structural parameters of various amorphous silicon films during 500-580^0C heat treatment. Amorphous silicon films were prepared by ion implantation, UHV and plasma assisted chemical vapor deposition. Deviations of atomic bonding angle from the crystalline value were determined from the TO-phonon spectrum FWHM.
(a) Structural relaxation process has been found to depend on the annealing temperature and transition into quasi-stable structures occurs rapidly with higher annnealing temperatures. However, such quasi-stable structures, were similar with various amorphous silicon films as far as they were not intentionally doped. Deviations in the atomic bonding angle from the crystalline silicon (109^0) has been changed from the initial-11^0 to 7-8^0 after relaxed into quasi-stable structure. (b) Structural relaxation occurs most easi
ly in the room temperature ion implanted amorphous silicon, whereas low temperature implanted and UHV deposited amorphous films were observed to show slow relaxation. (C) Amorphous films prepared by high dose Ge implantation indicated reverse shift of TO spectrum peak with respect to undoped films. Atomic bonding angle deviations also showed slight increase by anneal
2. Amorphization of crystalline silicon through self ion implantation
Atomic bonding angle deviations were determined with self ion implanted crystalline silicon surface. Si implantation with dose between lE14 to lE15cm^<-2> at the room temperature and with fixed dose at the substrate temperature of 23 to -200^0C was used to prepare samples. With increase of dose, angle deviationsincreased from 6^0 to 11^0. Also, lower substrate temperature implanted samples showed large devition angle. These facts show structures of amorphous films depend largely upon their preparation processes.
With the model of vacancy introduction into perfect silicon unit lattice, structural relaxation process has been simulated by computer cakulations. Atomic potential utilized in the model was a Tersoff type, and 16 vacacies were introduced into 216 silicon atomic lattice configuration. Atomic bonding angle deviations and radial distribution functions were calculated when vacancies form divacancies and/or quadravacancies. Calculated results supported the measured relaxation.
4. Calculation of phonon density function of amorphous silicon
Computer program has been developed to calculate amorphous silicon phonon density function by using the recursion method developed by Haydock and others. Relations between structural informations of the amorphous films and their Raman spectrum has been discussed.
Research Output (11results)