VISUAL DETERMINATION OF THICKNESS AND POROSITY OF POROUS SILICON LAYERS

Optical characteristics of porous silicon layers of different thicknes s acid porosity are simulated and interference spectra are calculated. The results are presented as curves on a colonimetric diagram. For th icknesses up to 500 nm, analysis of colors has shown that the interfer ence color is directly related to the product of thickness and porosit y of porous silicon layer. Practical techniques, which enable one to v isually define thickness (or porosity) of a porous silicon layer at kn own porosity (or thickness), are developed, The method has high accura cy and is easy to use, it does not need destruction of the sample and allows one to make the control in selected local areas, A similar tech nique is useful for in-situ analysis during the porous silicon anodiza tion process. The method applied to dried porous structures and those filled by water allows determination of both thickness and porosity of a porous silicon layer at one time. (C) 1997 Elsevier Science S.A.