Phenols or polyphenols of low molecular weight are added to novolak resists to increase the dissolution rate. They function as dissolution promoters by introducing additional hydrophilic percolation sites (OH-groups) into the system. All low molecular weight phenols act as dissolution accelerators, but some are also able to increase the image contrast of the material, i.e. the difference in dissolution rate between exposed and unexposed areas of the resist film. Additives that function in this way are those that are included in the phenolic clusters formed by the inhibitor. It appears that the criterion for inclusion in the clusters is the acidity of the OH-groups of the additive.
"Dissolution promotion in novolac-diazoquinone resists", Proc. SPIE 3049, Advances in Resist Technology and Processing XIV, (7 July 1997); doi: 10.1117/12.275854; https://doi.org/10.1117/12.275854