High-energy ion implantation: an alternative technology for micromachining three-dimensional GaAs structures

We present an alternative technology to micromachine GaAs using deep ion implantation for MEMS applications. Energetic low dose nitrogen ions were used to implant deeply into n-type GaAs substrate. After annealing at 600/spl deg/C the nitrogen implanted n-GaAs top layer was converted to semi-insulating GaAs. A pulsed electrochemical etching process was used to selectively remove n-GaAs layer as mechanical membrane structure. Various GaAs microstructures, such as cross-bridge, coiled and corrugated membranes have been successfully fabricated using this unique micromachining technology. By increasing the ion doses, the GaAs will be heavily damaged. The damaged GaAs shows much higher etch rate compared to the un-implanted GaAs using proper etch solutions and can be therefore used as sacrificial layer. In the fabrication of a capacitive pressure sensor, the air gap between two electrodes has been formed by releasing locally damaged GaAs.