Bleaching of photoresist is a positive issue: once exposed, the resist becomes transparent for the lower part, thus the light can reach also the bottom of the resist, allowing full develop afterwards
The absorbtion coefficient of the resist - a () for light must be low enough not to absorb all light in the upper part, otherwise, the light will not be sufficient to activate the photosensitive element in the lower regions
The resist can be developed only for a longer exposure time, in order to solve the above problem
Topology - due to the topology, there is a thickness nonuniformity in the resist, as it can be seen in the picture below
Solution: to apply a planaryzing polymer applied first, however, this will increased the process complexity
Substrate preparation
) for light must be low enough not to absorb all light in the upper part, otherwise, the light will not be sufficient to activate the photosensitive element in the lower regions
