Reactive ion etching and plasma etching of tungsten

Abstract

Tungsten etching has been studied in audio frequent plasmas with NF 3-O 2 and SF 6-O 2 mixtures. The influence of etch mode, gas flows, pressure and power has been investigated. It is possible to etch tungsten chemically but large concentrations of free fluorine are needed. These are supplied more easily by NF 3 than by SF 6. During chemical etching with NF 3 fluorine diffuses into the tungsten. When in contact with air, the fluorine is replaced by oxygen, forming a tungsten oxide layer, which withstands further chemical etching.