The solid phase crystallization of amorphized Si films on quartz substances is studied by means of the transmission electron microscope observation of grain growth. The amorphous Si films are prepared by Si ion implantation into polycrystalline Si films deposited by low-pressure chemical vapor deposition. It has been found that the twin formation in grains at the early stage of the crystallization accelerates the growth rate preferentially in a 〈112〉 direction. During the twin growth about a given 〈112〉 direction, other twins also grow from the twin boundary dendritically in some other 〈112〉 directions, leading to the formation of a large grain of dendritic structure.

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VoW. 125, No. 4 THERMAL OXIDATION KINETICS 579 pendence. Linear rate constants, B/A, for (111) silicon are 1.68 times the (1O0) silicon values. Activation energies are 0.78 and 2.05 eV for the parabolic and linear rate constants, respectively. Again, these values correspond favorably with wet 02 bubbler results. The 1.68 ratio between (111) and (100) linear rate constants was applied to the dry oxygen data recently obtained, and the line drawn for (100) silicon provides a reasot, able fit for the Arrhenius-plot data points. Oxidation kinetics were also determined for mixtures of 5 volume percent (v/o) HC1 in H20 using the pyrogenic system. Other process conditions were the same as indicated above for H20 oxidations. It was found that the only change in the oxidation process due to the HC1 addition is a decrease in rate constants approximately equal to the HC1 concentration in the oxidation ambient. Apparently no chlorine species is incorporated in the oxide during H20/HC1 oxidations (10). This fact plus the probability that HC1 does not react with the H~O would indicate ~ that the HC1 species itself does not enter into the reaction directly in either H20/HC1 oxidations or in the OJHC1 oxidations discussed previously (4, 18). If this is true, the previous proposal that the reaction products H20 and C12 are the primary species affecting O2/HC1 oxidation kinetics (18) is corroborated.The results of this investigation also indicate that small HC1 additions to H20 oxidation ambients provide beneficial effects because of the gettering or complexing of alkali impurities in the quartz system. In addition, more uniform oxides with fewer defects are produced. The question of possible effects on the oxide charges due to free hydrogen in the pyrogenic system must yet be resolved.

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