Lift-Off Process Using Chemical Blowing Agents in Manufacturing Chip Packaging Structures
Original Publication Date: 1988-Feb-01
Included in the Prior Art Database: 2005-Feb-14
Lift-off processes are used to form fine interconnections on various surfaces. In the past lift-off processes have employed a lift-off sequence which was slow. One employed either a soluble polymer or silicon oxide layer which was dissolved in an appropriate solvent after metal deposition so that the metal film on the undesired area could be removed. During the lift-off process, the solvent penetrated between the substrate and undesirable portion of the metal film on top of the lift-off layer. The solvent dissolves the lift-off layer (polysulfone, polymer or silicon oxide). Since the thickness of the lift-off layer was very thin in comparison with its top surface area and the solvent attacks only from the sidewall of the lift-off layer, a long dissolution time is required.