Method of making a grayscale reticle using step-over lithography for shaping microlenses

A method of fabricating a grayscale reticle, comprising:

• preparing a quartz wafer substrate;
• depositing a layer of SRO on the top surface of the quartz substrate;
• patterning and etching the SRO to form an initial microlens pattern using step-over lithography;
• patterning and etching the SRO to remove a predetermined amount of SRO;
• depositing an opaque film of the SRO;
• patterning and etching the opaque film;
• depositing and planarizing a planarizing layer having a thickness equal to the predetermined amount of SRO removed, wherein the planarizing layer is formed of a material having a refractive index with a real part matching a refractive index with a real part of the SRO;
• cutting the quartz wafer into pieces having a size smaller than that of a selected blank reticle;
• bonding the pieces to selected reticle blanks to form a grayscale reticle;
• and
• using the grayscale reticle to form a microlens array on a photoimager.