New method to release channels for Ge gate-all-around transistors.

What is it about?

Today, silicon nanowires transistors are the most novel semiconductor devices. In the future, silicon will be replaced by germanium. The nanowires are formed by first growing a layer stack of two different semiconductor materials. After a patterning step, one material is selectively etched away, leaving suspended nanowires of the other material. We present an alternative to the existing fabrication process. A different sacrificial material in the layer stack enables to use a different etch approach. SiGe/Ge multilayers are replaced by GeSn/Ge and the selective etch is done by vapor etching instead of wet-etching. The release of the Ge channels can be combined with the next processing step, which is the deposition of a Si capping layer.

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Why is it important?

The process is preferred to etching in wet chemicals since it is more environmental friendly, it reduces costs (less fabrication steps as two steps are being combined) and unwanted Ge oxidation is avoided. As it is a dry etching process, Ge surfaces remain free of contaminants, which would deteriorate device properties.