RESIST PROFILE ENHANCEMENT IN NEAR-FIELD HOLOGRAPHIC PRINTING USING BOTTOM ANTIREFLECTION COATINGS

Holographic lithography and near-field holography (NFH) used to print gratings in the manufacture of DFB lasers are limited in the quality o f the resist profiles due to the effects of vertical standing waves oc curring within the photoresist layer. We report on various attempts to produce improved grating profiles in photoresist which can thereby di rectly serve as dry etch masks for transferring gratings into semicond uctors. Trials include both thin dielectric layers as well as bottom a ntireflection coatings (BARC's) to mitigate interference effects. We s how that among these, a bilayer BARC/photoresist method is both practi cal and can greatly improve resist profiles.