SPECTROELLIPSOMETRY AND ELECTRON-SPECTROSCOPY OF POROUS SI THIN-FILMSON P(+) SUBSTRATES

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