There are two types of photoresist, positive and negative resist, which are used in different applications. In positive resist, the exposed areas are solubly, in negative resist the exposed areas are insolubly for wet chemical development.
Characteristics of positive resists:
- excellent resolution
- stable against developers
- can be developed in aqueous developers
- bad resistance in etching or implantation processes
- bad adhesion on the wafer
Characteristics of negative resists:
- high sensitiveness
- fair adhesion
- excellent resistance against etch or implantation processes
- cheaper than positive resists
- lower resolution
- organic developers are needed (toxic)
For patterning of wafers in manufacturing, almost only positive resits are used. Negative resists were primarily used as a passivation which can be cured by ultra-violet radiation. If there is no specification in the text, a positive resist is the subject.