The mechanism of formation of microneedles on the silicon surface in fluorinated plasma via the cyclic etching-deposition process

Abstract

The mechanism of the formation of microneedles on the silicon surface in SF6/C4F8 plasmas in the two-stage cyclic etching/deposition process is proposed. By means of scanning electron microscopy, it was shown that microneedle growth nuclei are nanosized entities of carbon nanofilaments. They are formed on the Si surface during the reactive ion etching of a fluorocarbon polymer film. As the number of etching/deposition cycles increases, the length of filaments increases and, beginning from a certain cycle, the filaments form a network of the fluorocarbon micromask needed for the formation of microneedles. A simulation of the microneedle formation by means of the hybrid string-cell representation of the profile and the Monte Carlo representation of the particle flux showed satisfactory agreement with the experimental data and the proposed mechanism.