The present disclosure relates to a method to form a plurality of openings within a substrate with a single photo exposure and a single etch process. A photoresist layer is disposed over a substrate and aligned with a photomask, wherein the photomask comprises a transparent area, a grayscale area, and an opaque area. The photomask and substrate are exposed to radiation comprising a single illumination step to form a first 3-dimensional pattern within the photoresist layer. The 3-dimensional pattern comprises a first opening comprising a first thickness formed by transmitting the radiation through the transparent area with full intensity, and a second opening comprising a second thickness formed by transmitting the radiation through the grayscale area with partial intensity. The 3-dimensional pattern is transferred to form a plurality of openings of varying depths within the substrate through a single etch step.