Localized and ultrahigh-rate etching of silicon wafers using atmospheric-pressure microplasma jets

Abstract

A miniaturized very-high-frequency- driven inductively coupled plasma jet source has been developed for the production of high-temperature and high-density plasmas in a small space, and its application to the localized and ultrahigh-rate etching of silicon wafers has been studied. The developed plasma source consists of a 1-mm-diam discharge tube with a fine nozzle of 0.1 mm in diameter at one end and a three-turn solenoidal antenna wound around it. The electron density of atmospheric-pressure argon plasma jets blowing out from the nozzle was estimated to be ${10}^{14}{\text{–10}}^{15}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ by means of optical emission spectroscopy. By the addition of halogen gases into the downstream region of argon plasma jets, high-speed etching of fine holes of several hundreds μm in diameter has been investigated. The highest etch rates of 4000 μm/min and 14 μm/min have been achieved for silicon wafers and fused silica glass wafers, respectively.