A novel refractive silicon microlens array using bulk micromachining technology

Abstract

We have developed refractive Si microlens array. Boron diffusion and etching selectivity with respect to boron density in an ethylenediamine pyrocatechol (EDP) etchant are utilized. When the EDP etchant meets the heavily boron doped p++ layer (above 2.5×1019 atoms/cm3), the etching is nearly self-stopped. As a result, Si microlens is formed. Diffusion diameter and diffusion parameters such as temperature/time controlled the diameter, height, and focal length in ranges of 10-55, 2.5-7.5, and 45-79 μm, respectively, and the measured focal spot size is 3.8 μm, compares to a theoretical diffraction-limited spot size of 3.3 μm.