Highly anisotropic etching of tungsten-nitride for an X-ray mask absorber with an inductively coupled plasma system

Inductively coupled plasma (ICP) etching of a WNx film using an auxiliary r f plasma source is applied for preparing X-ray mask absorber patterning. WN x is effectively etched with SF6 gas plasma and the addition of Ar and N-2 results in higher dissociation of the SF6 gas and sidewall passivation effe ct, respectively. Pattern distortion observed for high-aspect-ratio pattern s is minimized by multistep etching and an O-2 plasma treatment process. As a result, 0.18 mu m WNx line and space patterns with vertical sidewall pro files are successfully fabricated.