Focused ion beam repair of lithographic masks

Abstract

The application of focused ion beams to the repair of defects in photomasks is reviewed. Commercial mask repair tools are available which can focus a gallium ion beam to a diameter of 0.25 μm or less at a current density of 0.5A/cm2. These systems scan the ion beam over the mask to produce a secondary electron or secondary ion image of the defective region. Opaque defects are removed by physical sputtering. Clear defects are repaired by either ion machining a refractive structure into the glass substrate, or decomposing a hydrocarbon to form an opaque film on the substrate. Examples demonstrating the repair of opaque and clear defects are presented. The effect of the ion imaging and repair process on the optical properties of the glass substrate is also described. © 1989.