Image Reversal Lift-Off Process Using a Release Layer
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
The lift-off mask is hardened by UV radiation and heat, while the exposed areas of the polysulphone release layer are decomposed. Using the known image reversal lift-off process, photoresist mask 3 is formed on substrate 1 which is covered by a polysulphone release layer 2 (Fig. 1). The photoresist used is an m-cresol novolac resin which is transparent at a wavelength > 300 nm. Mask 3 is hardened by UV irradiation and heating to about 200oC. Under these conditions, the exposed areas of polysulphone layer 2 are decomposed (Fig. 2). Then, metal 4 is blanket-deposited at substrate temperatures of up to 200oC (Fig. 3). Finally, polysulphone layer 2, hardened lift-off mask 3 and overlying metal 4 are lifted off by dissolving the polysulphone, using, for example, N-methylpyrrolidone.