Effect of sample doping level during etching of silicon by fluorine atoms

The rate of silicon etching by XeF2 is dependent on the type of dopant and the doping level. Soft-x-ray photoemission was used in an effort to elucidate the mechanism responsible for this phenomenon. Si(111) samples were subjected to sufficient XeF2 to reach the steady-state etching regime, and spectra were collected of the fluorosilyl reaction intermediate species that form on the surface. Samples that were lightly doped (1017 cm-3) showed virtually no difference between p and n doping, while heavily doped samples (1020 cm-3) showed a marked difference. The heavily doped n-type sample had a slightly thinner reaction layer than did the lightly doped samples, while the heavily doped p-type sample had a much thicker layer, in which the composition of the layer was also changed. These results are discussed in terms of possible reaction mechanisms. © 1988 The American Physical Society.