Ultrafast laser based hybrid methodology of silicon microstructure fabrication for optoelectronic applications

As an alternative approach to conventional lithography based fabrication, simple methodology of ultrafast laser writing followed by chemical processing for fabrication of silicon microstructures is studied and presented. Laser fluence and number of pulses dependent laser-matter interaction study reveals several concurrent extreme nonlinearities that influence the structural morphology in both longitudinal and transverse directions. High intensity femtosecond pulse propagation produces inevitable structural features, such as quasi aperiodic surface textures, V-shaped craters, re-casted melt and debris. To minimize such undesired effects, isotropic and anisotropic chemical etching processes have been systematically optimized. Such hybrid protocols resulted into definite microstructures, with surface quality comparable to those obtained from other lithographic fabrication methods. The proposed methodology is expected to provide control over desired feature sizes, for large-scale and cost-effective fabrication of microstructures for many optoelectronics applications.