The etching of silicon carbide in inductively coupled SF6/O2 plasma

Abstract

The etching mechanisms of silicon carbide in an inductively coupled plasma (ICP) reactor using a SF6/O2 gas mixture, have been investigated using optical emission spectroscopy (OES) and Langmuir probe measurements. The etching is shown to be ion induced with a high degree of anisotropy. An optimum etch rate is achieved with 20% oxygen content within the gas mixture. By studying the independent influence of the ICP power and the substrate bias voltage on the ion current density, as well as the fluorine and oxygen radical densities in the plasma, the etch mechanism is found to be dominated by the number of ions bombarding the SiC surface. The steady state sputter yield observed at P>0.7 Pa, despite the increase in F radical concentration indicates the dominant role of ion bombardment in this etch regime, while at P<0.7 Pa, the etch mechanism is limited by the number of F radicals in the plasma. The OES results have shown that the etch rate is dependent upon the concentration of reactive radicals present with the [F]/[0] ratio = 8 at the optimum. Whilst using the optimum gas composition, the parameters which dominate the physical side of the reaction, ICP power and bias voltage, produce an increase of the etch rate as the potential difference between the substrate and the plasma is increased.