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Proposed bi-layer process to further improve proximity exposure performance for lift-off processes

Monday, Nov 19, 2018

In order to overcome discovered pattern resolution limitations using proximity lithography with the predefined Asteroid process materials (negative tone resist, bright field mask layout), EVG developed and studied an alternative bi-layer process approach for the desired lift-off application and the fine pitch structure of the Asteroid ROIC.

The bi-layer resist concept is based on switching the lithography exposure mask polarity to darkfield and using positive tone resist as the top resist layer.

For the specific ROIC mask layout design used, very promising resist undercut structures have been realized. Good control of the undercut parameter could be demonstrated by variation of resist material and resist development parameter.