KINETIC ISOTOPIC EFFECTS IN THE ANISOTROPIC ETCHING OF P-SI(100) IN ALKALINE-SOLUTIONS

The etching mechanism of silicon has been investigated by measuring th e H/D-kinetic isotopic effect on dissolution rate. The etching rate of p-Si(100) was measured using optical profilometry. It was found that in 2 M KOH + H2O and 2 M NaOH + H2O it was approximately twice as larg e as in 2 M KOD + D2O and 2 M NaOD + D2O. The existence of a H/D-isoto pic effect shows that the cleavage of the Si-H bond represents the rat e determining step in silicon etching. Calculations of the activation barriers from IR data for the Si-H and Si-D vibrations show that the o bserved isotopic effect reflects the nature of the transition state, i n which the Si-H bond is not completely broken. Both the chemical and electrochemical pathways for the dissolution process of silicon in alk aline solutions are discussed on the basis of the results presented. ( C) 1997 Elsevier Science S.A.