Role of Hydrogen for Microcrystalline Silicon Formation

Abstract

The role of hydrogen atoms in the formation process of hydrogenated microcrystalline silicon (μc-Si:H) by plasma enhanced chemical vapor deposition method has been investigated. Under the present conditions, the etching and the permeation of hydrogen atoms in the subsurface region do not cause the crystallization. The kinetics study of surface morphology and structure in the initial growth of μc-Si:H on an atomically flat substrate indicates that the onset thickness of island coalescence reduced under μc-Si:H formation condition. The results support the ‘surface diffusion model’ in which the surface diffusion of film precursors is enhanced by the sufficient hydrogen coverage of surface and by hydrogen atom recombination energy on the growing surface of the film.

Thin-Film Silicon –Growth Process and Solar Cell Application–

“…This causes the crystallization of the amorphous network through the formation of a flexible network, when there is a sufficient amount of atomic hydrogen in the subsurface region, without significant removal of Si atoms. 24,25) There have been many arguments in support of each model, however, one model alone does not sufficiently explain all the phenomena in the formation process of cSi:H. 25) Recently, more microscopic observations have been reported using in-situ diagnostic techniques, 26) and a detailed mechanism underlying the formation process of c-Si:H has been proposed. Figure 12 shows the surface-roughness evolution during film growth revealed by spectroscopic ellipsometry (SE) for three hydrogen-dilution ratios R of 0, 10, and 20.…”

Microcrystalline silicon.

“…During the hydrogen-plasma treatment, many atomic hydrogen are permeating in the subsurface (growth zone), giving rise to a crystallization of amorphous network through the formation of a flexible network with a sufficient amount of atomic hydrogen in the sub-surface region without remarkable removal process of Si atoms [24,25]. These three models have been carefully examined, and merits and demerits for each model have been discussed [25,26].…”

Thermodynamic model of nucleation and growth of plasma deposited microcrystalline silicon

“…There have been numerous proposals as to the role of hydrogen in promoting the nucleation and growth of c-Si in PECVD. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] However, these have tended to use ideas unique to the amorphous or Si:H system. This article attempts to provide a description of the nucleation and growth of c-Si within the standard framework of free energies and phase transformations in two-component systems.…”