Deep nitrogen implantation for GaAs microstructuring using pulsed electrochemical etching

We present deep ion implantation technology to fabricate the GaAs microstructures for microelectromechanical systems applications. 630 keV and 4 MeV nitrogen ions were used to implant deeply into an n-type GaAs substrate with doses of 2x10(14) and 1x10(15) cm(-2), respectively. The resistivity and I/V characteristics of implanted n-GaAs have been investigated as a function of the annealing temperature. The results demonstrate that the implanted n-GaAs surface layer annealed at 600 degreesC has the highest resistivity and maximum breakdown voltage. This layer is a semi-insulating layer and has a thickness of 1 and 2.5 mum for implantation with 630 keV and 4 MeV nitrogen ions, respectively. Deep-level transient spectroscopy measurement reveals that the EL2 trap contributes to the formation of semi-insulating GaAs layers. Rutherford backscattering measurements show that there is no significant crystalline damage in the nitrogen implanted GaAs layer. A pulsed electrochemical etching process has been developed to selectively remove n-GaAs, leaving the top patterned semi-insulating GaAs layer as mechanical microstructures. Using this technique, GaAs microstructures, such as cantilevers and cross bridges, have been successfully fabricated.