Fig. 3.64 : The sidewall profile in the case of image reversed lift off

The photoresists of the AZ 5200 series activates an amine that is already present in the resist. This amine bonds to the photogenerated acid, just as the ammonia does in the Oven. A flood exposure and development follows.

Fabrication of Masks :

Optical lithography requires the fabrication of a mask. Masks are glasses coated with a film in which the pattern is formed. Generally two types of masks are formed; resist-coated chrome masks and emulsion coated glasses. In the first one a layer of sputtered Cr about 100 nm thick coats the glass plate. Resist is then spun on the plate, and the exposure is made. After development, the Cr is removed from the unprotected areas with an acid etch, and an image of the pattern is left in the Cr. The exposure can be made with either an optical or an e-beam tool.