Anatomy of mu c-Si thin films by plasma enhanced chemical vapor deposition: An investigation by spectroscopic ellipsometry

A detailed analysis of the anatomy of microcrystalline (mu c-Si) films depo sited by plasma enhanced chemical vapor deposition from both SiF4-H-2 and S iH4-H-2 mixtures is performed by spectroscopic ellipsometry (SE). Specifica lly, the mu c-Si film anatomy consists of an interface layer at the substra te/mu c-Si bulk layer, a bulk mu c-Si layer, and a surface porous layer. Al l these layers have their own microstructures, which need to be highlighted , since it is this overall anatomy which determines the optical properties of mu c-Si films. The ability of SE to discriminate the complex microstruct ure of mu c-Si thin films is emphasized also by the comparison with the x-r ay diffraction data which cannot provide unambiguous information regarding the distribution of the crystalline and the amorphous phases along the mu c -Si film thickness. Through the description of the mu c-Si film anatomy, in formation on the effect of the growth precursors (SiF4 or SiH4) and of the substrate (c-Si or Corning glass) on the growth dynamics can be obtained. T he key role of the F-atoms density and, therefore, of the etching-to-deposi tion competition on the growth mechanism and film microstructure is highlig hted. (C) 2000 American Institute of Physics. [S0021-8979(00)00617-4].