Semiconductor microlenses fabricated by one-step focused ion beam direct writing

We fabricated a refractive semiconductor micro-lenses using a focused ion beam (FIB) direct writing technique. The simple one-step FIB process produced high-quality micro-lenses of silicon, the most popular and low cost semiconductor material used in optoelectronics. A spherical Si microlens with a nominal lens diameter of 48 /spl mu/m exhibited a radius curvature and focal length of 100 and 40 /spl mu/m, respectively. The maximum derivation between the measured and designed profiles is less than /spl lambda//100. The surface roughness, RMS, measured by use of atomic force microscope in 1/spl times/ 1 /spl mu/m/sup 2/ square area, is 1.1 nm. This microlens fabrication method could be readily applicable due to the simplicity in processing and the high-quality results.