Exposure method

An exposure method comprising the steps of:

• illuminating a mask that has a contact hole pattern using an illumination light;
• and
• projecting, via a projection optical system, the contact hole pattern onto a substrate to be exposed,
• wherein said contact hole pattern is a checker pattern that includes a plurality of periodic patterns, each of which has plural contact holes arranged in a first direction at a first pitch, and the plurality of periodic patterns are arranged in a second direction perpendicular to the first direction at a second pitch while shifting by half a pitch,
• wherein an effective light source formed on a pupil plane in the projection optical system by the illumination light has six poles,
• wherein a distance between centers of the six poles and an optical axis of the projection optical system is commonly a,
• wherein said centers of the six poles are located around the optical axis in a direction of an angle α to the first direction, wherein said angle α is 0, 2α, π−2α, π, π+2α, and 2π−2α,
• wherein Pxo/2=(Px/2)NA/λ, Pyo/2=(Py/2)NA/λ, α=tan−1(Pxo/(2Pyo)), and a=1/(4(Pyo/2)/sin(2α)) are satisfied, where Px is the first pitch, Py is the second pitch, NA is a numerical aperture of the projection optical system, and λ is a wavelength of the illumination light, and
• wherein three lights in diffracted lights from the contact hole pattern interfere mutually.