Spectroellipsometry and electron spectroscopy of porous Si thin films on p+ substrates

Porous Si layers (PSL) are perspective for microelectronics. PSL deposited on B doped p(+) type 10(-3) Omega cm Si substrates exhibit channel structure. Their properties are determined by the preparation conditions. The samples are characterized by spectroellipsometry (SE). A 3-layer model was developed resulting in good agreement with psi-Delta spectra, measured on as received, ion bombarded, HF treated and long time stored samples. Elastic peak electron spectroscopy (EPES) revealed the effects of HF treatment, producing stable Si-H bond on the surface. r(e)(E, P) elastic reflection spectra, measured in % units with a retarding field analyzer exhibited monotonous decrease with porosity P and energy E. HF treatment produced a dramatic decrease in r(eH)(EI P) intensities. r(eH)(E, P) spectra measured at E = 50 and 150 eV showed linear relationship with P below P < 60%. Above P > 60%, excess reflection occurs. The r(eH)(E, P) spectra were explained with the electron reflection on the intact Si surface area not covered by pores. Excess reflection is due to electrons escaping from the deep pores of large area, suffering multiple internal reflections and detected by the analyzer angular window. (C) 1998 Published by Elsevier Science S.A.