Solvents are the main component of all resists, with solvent contents ranging from 50% (thick resists) to up to 99% (spray resists). The first resists developed before 1980 still contained the health-hazardous solvents toluene or cyclohexanone. From 1980 onwards, standard positive resists were composed of a mixture of ethyl glycol acetate (EGA), butyl acetate (Buac), and xylene. This mixture of solvent (EGA), latent solvent (Buac) and non- solvent had particularly advantageous coating features. In the beginning of the 1990s it became evident that ethyl glycol acetate is potentially teratogenic (causing malformations of the embryo). EGA was consequently immediately replaced by propylene glycol-monomethylethyl acetate (PGMEA) (also called 1-methoxy-2-propyl-acetate or PMA). Worldwide, only pure PGMEA was now used instead of a mixture of different solvents. A few currently available resist types use ethyl lactate or butyrolactone as solvent. Spray resists contain in addition to a more or less low amount of PGMEA quick-drying solvents like acetone, methyl ethyl ketone (MEK) or butyl acetate (Buac). (see also “Solvents in e-beam resists“)

If resists are produced without surfactants, radial striations (wavy structures) may occur on the surface during spin coating. This can be prevented by varying the surface tension. Just like the classic soap (fatty acid salts), surfactants possess a hydrophilic and a hydrophobic part of the molecule. If specific surfactants are added to a resists, the surface is smoothened and the abovementioned striations during the coating step are avoided. The effect of the surfactant also depends on the solid matter content. Thicker resists require more surfactant to achieve the same result as for thin resists. The positive effect of the surfactant decreases over time, and radial striations may reappear in 1 – 2 year old resists. In this case, addition of surfactant will fix this problem.

Adhesion promoters are used for many substrates. The most popular adhesion promoter is hexamethyldisilazane (HMDS), an alternative offers AR 300-80 (diphenylsilane diole in PGMEA). A few resists like the resist-series AR-P 3100 already contain adhesion promoters on the bases of epoxides, which increases the adhesive strength considerably. This addition allows the coating of difficult surfaces (glass, quartz, GaAs), which can otherwise be coated only with difficulties even in the presence of HMDS or not at all.

In order to reduce stray radiation and thus to enhance resolution, dyes are added to the resists which absorbe within the range of the exposure wavelength (e.g. AR-P 3840).