Abstract: A method of forming a pattern in a photoresist includes forming a photoresist layer over a substrate, and selectively exposing the photoresist layer to actinic radiation to form a latent pattern. The latent pattern is developed by applying a developer composition to the selectively exposed photoresist layer to form a pattern. The developer composition includes a first solvent having Hansen solubility parameters of 15<?d<25, 10<?p<25, and 6<?h<30; an acid having an acid dissociation constant, pKa, of ?15<pKa<5, or a base having a pKa of 40>pKa>9.5; and a second solvent having a dielectric constant greater than 18. The first solvent and the second solvent are different solvents.