III-V-semiconductor-based surface-micromachined catilevers for micro-opto-mechanical systems

Abstract

ABSTRACT Surface micromachining processes based on III-V compound semiconductors are presented in this paper, in order to develop Micro-Opto-Electro-Mechanical systems (MOEMS). By fabricating micro cantilevers composed of seven InP/Air gap pairs, the major techniques of the surface micromachining are studied, including non-selective and selective etching, rinsing and drying. A severe problem of the sticking phenomena during rinsing and drying is avoided by the implementation of the Critical Point Drying (CPD) method . Keywords: MOEMS, Non-selective and selective etching, Sticking, Critical Point Drying (CPD) 1. INTRODUCTION Micro-Opto-Electro-Mechanics System (MOEMS) is an integration of photonic, microelectronic and mechanical devices on a compatible substrate. Because of its advantages in precision, compatibility and mass production, MOEMS is very promising in optics and optoelectronics fields. Surface micromachining is one of the most important techniques in fabrication of Micro-Opto-Electro-Mechanical devices. Many developments have been reported on this technique in field of silicon-based materials. III-V compound semiconductors offer a number of superiorities over silicon because of their instinctive features and advantages of opto-mechanical sensitivity, direct bandgap and heterostructure-based quantum effects, which make them to be good candidates for optical devices mostly dedicated to long wavelength applications, such as lasers, photodiodes, phototransistors, optical filters, and photodetectors. Hence, surface micromachining for III-V semiconductors based Micromachined devices is of vital significance in the fabrication of MOEMS devices, especially for fiber communication systems, optical integrations and other long wavelength applications [1]. In the fabrication of most micromachined devices, the key micromachining step is to produce released mechanical layers, such as suspended cantilevers and thin membrane. In this paper, a micro cantilever structure composed of seven InP/Air gap pairs was fabricated as an illustration, describing main techniques of surface micromachining used in III-V semiconductors related devices, including non-selective and selective etching, rinsing and drying process. The chemical selective and non-selective etching characteristics of InP and InGaAs in different solutions are investigated. Appropriate