A first photoresist pattern and a second photoresist pattern are formed over a substrate. The first photoresist pattern is separated from the second photoresist pattern by a gap. A chemical mixture is coated on the first and second photoresist patterns. The chemical mixture contains a chemical material and surfactant particles mixed into the chemical material. The chemical mixture fills the gap. A baking process is performed on the first and second photoresist patterns, the baking process causing the gap to shrink. At least some surfactant particles are disposed at sidewall boundaries of the gap. A developing process is performed on the first and second photoresist patterns. The developing process removes the chemical mixture in the gap and over the photoresist patterns. The surfactant particles disposed at sidewall boundaries of the gap reduce a capillary effect during the developing process.