REAL-TIME TEMPERATURE, OPTICAL BAND GAP, FILM THICKNESS, AND SURFACE ROUGHNESS MEASUREMENT FOR THIN FILMS APPLIED TO TRANSPARENT SUBSTRATES

摘要

A method and apparatus (20) used in connection with the manufacture of thin film semiconductor materials (26) deposited on generally transparent substrates (28), such as photovoltaic cells, for monitoring a property of the thin film (26), such as its temperature, surface roughness, thickness and/or optical absorption properties. A spectral curve (44) derived from diffusely scattered light (34, 34') emanating from the film (26) reveals a characteristic optical absorption (Urbach) edge. Among other things, the absorption edge is useful to assess relative surface roughness conditions between discrete material samples (22) or different locations within the same material sample (22). By comparing the absorption edge qualities of two or more spectral curves, a qualitative assessment can be made to determine whether the surface roughness of the film (26) may be considered of good or poor quality.