ADVANCED LIFTOFF PROCESSING
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-22
Advance single layer liftoff processing has been developed to reduce the cycle time, minimize process variation and produce an environmentally safe process. This paper will present the key elements of two liftoff processes developed for use in the manufacture of sem- iconductor devices. The advance processes have been labeled "Polyvinyl Alcohol Liftoff' and "Sequential Develop Liioff: Historically the main stay used in single layer photoresist liftoff processing has been the use of a proc- ess described here as "Chlorobenzene liioff' similar to that described by Hatzakis, Canavello, Shawl. Chloro- benzene liftoff processing takes advantage of the use of a solvent in which the surface properties of the resist change during development. The exposed chloroben- zene surface development rate of the novalad positive resist used, AZ 13702, would be reduced with respect to the bulk resist development rate. Increased exposure to chlorobenzene and temperature will promote the "lip" formation at the top of the resist opening to produce a clean Ii!?& protile for metalization masking during dep- osition ofthe metal. This lip will produce the clean break of metal over the photoresist step and allow the removal of the resist with the unwanted metal when placed into resist-soluble solvents after metaliiation. Refer to Fig- ure 1 for the process step diagram for "Chlorobenzene Lift&?' Note: see Figure 4 for resist lip and profile observation.