Pulsed Laser Processing of Shallow Micro-Optical Structures

Pulsed UV laser machining is an established method for production of 2.5D and 3D features in a wide variety of materials. In addition to direct laser patterning by ablation, exposure of photoresist using pulsed lasers can eliminate the need for large area contact photomasks. Half-tone machining, either by ablation or exposure, allows the production of high quality shallow features where the surface roughness from other laser machining techniques would be unacceptable. Such features could be used as anti-reflection surfaces for mobile display devices. Features produced by lithography typically exhibit low surface roughness but have more complex fabrication processes. Here, the surface roughness of shallow features produced by half-tone lithography and half-tone ablation is investigated for a photoresist. Similar surface profiles are achieved for each technique and roughness levels are comparable for both.