Method of manufacturing semiconductor package

A method of manufacturing a semiconductor package includes forming a plurality of conductive patterns on a substrate, forming a photoresist film over the substrate to cover the plurality of conductive patterns, forming a photoresist pattern from the photoresist film by a photolithography process using a photomask that includes a transparent area, a light-shielding area, and a semi-transparent area transmitting only a portion of light incident thereon, wherein the photoresist pattern includes a via hole, which exposes one conductive pattern, and a recessed portion, which has a lower surface exposing a portion of the photoresist pattern, forming a conductive post in the via hole, and removing the photoresist pattern by using a photoresist stripping composition.