EXPOSURE METHOD AND PATTERN FORMATION METHOD

PROBLEM TO BE SOLVED: To provide a pattern formation method for forming a guide with high accuracy and obtaining a desired micro phase separation pattern.SOLUTION: A pattern formation method according to an embodiment comprises the steps of: irradiating a photo mask where a periodic pattern having openings whose centers are arranged so as to be capable of being described with a two-dimensional hexagonal lattice is formed, with illumination light; and performing exposure by projecting diffraction light from the photo mask on a substrate through a projection optical system. The illumination has first to third light emitting regions. The photo mask has a first opening and second to seventh openings whose center positions are at vertex positions of a regular hexagon whose center position is at the position of the first opening. A direction in which the illumination light enters the photo mask is on three planes determined by the first opening, the second, fourth, and sixth openings, and optical axis; and includes a direction inclined at an angle sin(2 λ/3 Pn) to the optical axis, where λ is a wavelength of the light, P is an on-substrate reduced value of an interval between the center of the first opening and the centers of the second to seventh openings, and n is a refraction index of a medium between the projection optical system and the substrate.