But suppose the metal cannot be etched, or only wet etched, which is not very precise for small features. The preferred technique is lift-off. In lift-off, the resist is patterned first, and then the metal is evaporated over the resist. The resist is then dissolved away in a solvent, carrying the unwanted metal with it. However, the normal positive resist profile presents a problem of sidewall slope as shown in figure.

Fig. 3.62: The sidewall profile in the case of lift off