Double Layer Lift-Off Process for Packaging
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
For packaging applications, the present process has the advantages of combining the function of a dry etch barrier with that of a release layer and giving a homogeneous, adhesion-promoting, non-cracking intermediate layer. This layer can be simply coated or removed with common, approved solvent systems, eliminating swelling of insulating layers and reducing toxicological hazard. Typically, the process can be practiced as follows: 1. Coat and thermally fix the dielectric layer. 2. Coat with poly(silastyrene) copolymer (PSS) from o-xylene solution and bake. 3. Coat with imaging layer, pre-bake and expose conventionally. 4. Develop conventionally. 5. Plasma etch with CF4/O2/He/H2 to pattern exposed PSS. 6. Reactive ion etch with O2 to pattern masking layer. 7. Deposit metal. 8. Lift-off excess metal and PSS etch barrier. 9.