Formation of microstructures on silicon surface in a fluorinated plasma via the cyclic etching-passivation process

The conditions and causes of formation of microneedles and columnar structures on the surface of silicon during deep anisotropic etching in an SF₆/C₄F₈ plasma in the two-stage cyclic mode were determined. The appearance of microstructures is accelerated with an increase in the thickness of the fluorocarbon film formed on the silicon surface at the step of passivation in a C₄F₈ plasma and with an increase is the rate of etching the film in an SF₆ plasma. By means of X-ray photoelectron spectroscopy, it was shown that the formation of carbon residues of fluorocarbon film etching on the Si surface is enhanced under these conditions. Building-up on the surface in the cyclic process, the residues as a micromasking coating lead to the formation of microneedles and columnar structures.