F and O radicals and ion energy distribution in etching of silicon via hole in a weakly-magnetized, inductively-coupled SF6/O2 plasma

Abstract

In this article, the effects of the magnetic field on the through-silicon-via (TSV) etching characteristics in an inductively-coupled plasma (ICP) were investigated and the results were compared with those in an unmagnetized ICP. The densities of the radicals in the SF6/O2 plasma were measured by using actinometry, and the ion energy distribution and flux of the Ar plasma were determined by using an ion energy analyzer in order to understand the differences in etching behaviors. The silicon etching rate in the M-ICP was three times faster than that in the unmagnetized ICP under the same RF power and gas conditions. However, the etch anisotropy in the M-ICP was rather poor compared to that in the ICP. In order to observe differences in the etching characteristics, we varied the SF6/O2 gas mixing ratio and the pressure. Lowering pressure at the optimal ratio for the SF6/O2 gas mixture influenced the ratio of F radicals to O radicals and the mean free path of ions. Consequently, a high etching rate with good anisotropy in TSV etching could be achieved in a M-ICP.