Pattern-formation methods comprise: (a) providing a substrate; (b) forming a photoresist pattern over the substrate; (c) applying a pattern treatment composition to the photoresist pattern, the pattern treatment composition comprising a solvent mixture comprising a first organic solvent and a second organic solvent, wherein the first organic solvent has a boiling point that is greater than a boiling point of the second organic solvent, and wherein the first organic solvent has a boiling point of 210° C. or more; and (d) thereafter heating the photoresist pattern. The methods find particular applicability in the manufacture of semiconductor devices.