Liftoff is a processing technique often preferred for patterning metal thin films. In a liftoff process, the resist is patterned first, and then the metal film is deposited. After metal deposition, the resist is dissolved and â€“ if the process has been optimized to insure poor metal step coverage - the unwanted metal is removed (â€œlifted offâ€) from the regions where the remaining resist is dissolved. Liftoff is preferable for difficult to etch metals, in cases where the metal etch has a poor selectivity relative to underlying layers and in situations that require minimizing plasma or acid exposure of underlying layers. Liftoff can also enable fine feature metal patterning with limited process tools since the minimum feature size is dependent primarily upon the resist process rather than upon the performance of the resist and a metal etch system. The goal of this work was to define a baseline liftoff process for use by a large group of researchers with a broad range of metals and a constantly changing set of deposition conditions. Therefore, this work attempted to identify a generally preferred resist system without testing with a specific metal deposition process; whereas, optimization of a specific liftoff process would include detailed characterization of the resist and the metal deposition. Several methods of liftoff were examined and results will be reported.
Project end date: 08/16/07