Dual Layer Photoresist and Back Sputtering Applied in Lift-Off Technique

Lift-off has been widely used in microfabrication process. In normal lift-off process, after photolithography and developing, a thin layer of residua will remain on the exposed substrate. To remove the residua, descum and back sputtering are required before metal sputtering. However, because of the high temperature of descum process and high energy induced by ion bombardment during back sputtering, the up inner angle of photoresist will increase in normal lift-off process. The metal films will deposit on the sidewall of the photoresist, and adhere to the substrate even after the photoresist removal. In order to overcome these problems, a lift-off process adopting dual layer photoresist is introduced in this paper, and high quality metallic pattern could be made.