Patent ID: 8867024

Claim:
A system for exposing a resist layer with regions of photosensitivity to an image in a lithographic process using a high numerical aperture imaging tool comprising: a substrate having thereover a layer reflective to the imaging tool radiation; a resist layer having a region of photosensitivity over the reflective layer, the resist layer having a thickness; wherein the imaging tool is adapted to project radiation containing an aerial image onto the resist layer, with a portion of the radiation containing the aerial image passing through the resist layer and reflecting back to the resist layer, the reflected radiation forming an interference pattern in the resist layer of the projected aerial image through the resist layer thickness, and wherein the thickness and location of the resist layer region of photosensitivity with respect to the reflective layer are selected to include from within the interference pattern higher contrast portions of the interference pattern in the direction of the resist thickness, and to exclude lower contrast portions of the interference pattern in the resist thickness direction from said resist layer region of photosensitivity, to improve contrast of the aerial image in said resist layer region of photosensitivity.