Image Reversal Using Positive Photoresist
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
Submicron images can be accurately constructed with electron beam exposure of positive photoresist by coating the photoresist on a planarization layer of polyimide, placing a protective material over the exposed and developed areas and etching the unprotected polyimide. In Fig. 1, wafer 1 is spin-coated with a 1-3 um layer of polyimide 2 that is baked at 200oC for 30 minutes to serve as planarization and masking. Positive photoresist 3 is applied and defined conventionally with an electron beam. A barrier layer 4 of 2000-3000 Ao of hexamethyldisilizane (ppHMDS) is deposited at 90oC over the photoresist. Next, layer 5 of planarizing polyimide is spin-coated to a thickness of 3 um and baked at 200oC for 30 minutes for reflow and to eliminate cracking. Polyimide layer 5 is etched exposing the barrier coating 4, as shown in Fig.