Diagnostics of expanding mesoplasmas originated from a miniaturized inductively coupled plasma and their application to Si etching

A miniaturized inductively coupled plasma (m-ICP) was generated at atmospheric pressure and introduced into an expansion chamber at a reduced pressure ranging from 10 to 1000 Pa to produce expanded mesoplasmas. The fundamental parameters of the m-ICP and the downstream mesoplasma were investigated by optical emission spectroscopy and Langmuir probe measurement. When the m-ICP entered the expansion chamber, it diffused into the surrounding area and the electron density decreased from 10(13) to 10(9)-10(10)cm(-3). Furthermore, Si etching in mesoplasmas was performed by adding SF6 to Ar plasmas. By changing the gas pressure, anisotropic etching with a vertical-to-horizontal etch rate ratio of 2.5 was achieved at 60 Pa with a vertical etch rate of 2.7 mu m/min. In addition, the anisotropy was improved to 8 by introducing 10 sccm H-2 into the Ar/SF6, which is ascribed to the reduction of sidewall undercutting resulting from the scavenging effect of fluorine atoms by atomic H. (C) 2014 The Japan Society of Applied Physics