In some embodiments, a method of controlling a photoresist trimming process in a semiconductor manufacturing process may include forming a photoresist layer atop a first surface of a substrate, wherein the photoresist layer comprises a lower layer having a first pattern to be etched into the first surface of the substrate, and an upper layer having a second pattern that is not etched into the first surface of the substrate; trimming the photoresist layer in a direction parallel to the first surface of the substrate; measuring a trim rate of the second pattern using an optical measuring tool during the trimming process; and correlating the trim rate of the second pattern to a trim rate of the first pattern to control the trim rate of the first pattern during the trimming process.