Photocrosslinking based on electrophilic aromatic substitution and its application to resists incorporating chemical amplification

A number of new resist materials which provide very high sensitivities have been developed in recent years. In general these systems owe their high sensitivity to the achievement of chemical amplification, a process which ensures that each photoevent is used in multiplicative fashion to generate a cascade of successive reactions. Examples of such systems include the electron-beam induced ring-opening polymerization of oxacyclobutanes, the acid-catalyzed thermolysis of polymer side-chains or the acid-catalyzed thermolytic fragmentation of polymer main-chains. Other important examples of the chemical amplification process are found in resist systems based on the free-radical photocrosslinking of acrylated polyols. The use of phenolic polymers in photocrosslinkable systems usually involves multicomponent systems which incorporate polyfunctional low molecular weight crosslinkers. The authors present their approach to resists chemical amplification via electrophilic aromatic substitution.