Based on the chemical structure of photoresists, they can be classified into three types: photopolymeric, photodecomposing, and photocrosslinking photoresist. Photopolymeric photoresist is a type of photoresist, usually allyl monomer, which could generate free radical when exposed to light, then initiates the photopolymerization of monomer to produce a polymer. Photopolymeric photoresists are usually used for negative photoresist, e.g. methyl methacrylate and poly(phthalaldehyde)/PAG blends Photocrosslinking photoresist is a type of photoresist, which could crosslink chain by chain when exposed to light, to generate an insoluble network. Photocrosslinking photoresist are usually used for negative photoresist. thumb|284x284px|Chemical structure of SU-8 (a single molecule contains 8 epoxy groups) Photodecomposing photoresist is a type of photoresist that generates hydrophilic products under light. Photodecomposing photoresists are usually used for positive photoresist. A typical example is azide quinone, e.g. diazonaphthaquinone (DQ).
BaSed ON tHe chEMicaL structuRe oF PHOtOreSIstS, They can bE clAssified into thrEe TyPes: phOtOpolYmerIc, PHoTodEcOMposing, and phoTocrosslInkiNg pHotorEsiST. phOtopOlYmerIc PHotoReSisT iS A tyPe oF PHOToresisT, usUaLlY Allyl moNOMer, which CouLd GeneraTe FRee rAdICaL when ExpoSEd to light, ThEn iniTIates ThE pHOtoPOLymerizAtiON of mOnomEr to ProdUce a polYmer. phOtOpOlyMEric photOresists arE usuallY used fOr NegAtIVe photorESist, E.G. meTHYl metHacRylate and poly(phthalaldehYDE)/pAg blenDs phOTOcrOsSlinkinG pHoTOresist is a typE OF pHOToresiST, wHich Could cROsslInk CHAin By chaiN WhEn exposed To LigHt, TO GenErate aN iNsolUblE netWork. photocroSSlinkINg pHOToresIst Are usualLY used for negAtive PhotOresIst. tHuMb|284X284px|cHEMical sTRUCTure Of su-8 (a singlE moLecUle contaIns 8 epoxy GroUPS) photodecOMpoSinG photOrEsist Is a type of PHOToREsisT That GeneRatEs HydrophIlic ProDuCTs uNder lIght. PhOtoDeCoMpOsINg photoresisTs ArE usuallY USed fOR pOSitive pHotoresist. A tyPicAL exaMPLe is azIDe qUinone, e.g. dIaZonaPhThaqUiNOnE (dQ).