Micromachined, reusable shadow mask for integrated optical elements grown by metalorganic chemical vapor deposition

Abstract

Precise three-dimensional control of micro-optical elements has recently been achieved using shadow masked metalorganic chemical vapor deposition (MOCVD) with an epitaxial mask. However, the epitaxial shadow mask used to deposit these precision micro-optics limits the size and shape of the available structures. In this work, a reusable shadow mask was fabricated by deep-Si reactive ion etching and employed in the growth of circular microlenses. This novel, reusable mask makes the shadow masked MOCVD process more rapid and less expensive and also allows more flexibility in the shape and size of the micro-optical elements that can be deposited. The micromachined shadow mask is held in place during growth by fusion bonding, it can be released by rapid cooling and it is easily cleaned for reuse. Microlenses with apertures as large as 500 μm, fabricated under the micromachined mask, did not flatten at the center and formed accurate quadric surfaces.