Editing Photoresist (section)

===Negative photoresist===
[[File:Polyisoprene negative photoresist.tif|thumb|346x346px|A crosslinking of a polyisoprene rubber by a photoreactive biazide as negative photoresist]]
[[File:Acrylate negative photoresist.tif|thumb|333x333px|A radical induced polymerization and crosslinking of an acrylate monomer as negative photoresist]]

A ''negative photoresist'' is a type of photoresist in which the portion of the photoresist that is exposed to light becomes insoluble in the photoresist developer. The unexposed portion of the photoresist is dissolved by the photoresist developer.

* Based on cyclized polyisoprene (rubber)
** variety of sensitizers (only a few % by weight)
** free radical initiated photo cross-linking of polymers
* Issues:
** potential oxygen inhibition
** swelling during development
*** long narrow lines can become wavy
*** swelling is an issue for high-resolution patterning
* Example: [[SU-8 photoresist|SU-8]] (epoxy-based polymer), good adhesion), [[KPR|Kodak Photoresist (KPR)]]

'''Modulation transfer function'''

MTF (modulation transfer function is the ratio of image intensity modulation and object intensity modulation and it is a parameter that indicates the capability of an optical system.