Abstract
Proton Beam Writing (PBW) is a direct write technique that employs a focused MeV proton beam which is scanned in a pre-determined pattern over a target material which is subsequently electrochemically or chemically etched and developed. The ultimate depth of the structure is determined by the range of the protons in the material and this allows structures to be formed to different depths. PBW has been successfully employed on etchable glasses, polymers, and semiconductor materials such as silicon (Si). This present thesis is a study on the feasibility of PBW in p-type GaAs, and compares experimental results with computer simulations using the Atlas(c) semiconductor device package from SILVACO. It has been established that hole transport is required for the electrochemical etching of GaAs using Tiron (4,5-Dihydroxy-m-benzenedisulfonic acid, di-sodium salt). PBW in GaAs results in carrier removal in the irradiated regions and consequently minimal hole transport (in these regions) during electrochemical etching. As a result the irradiated regions are significantly more etch resistant than the non-irradiated regions. The proton energy, proton fluence, beam current, etch current density, etch area, structural spacing, enclosed structures and post irradiated annealing were investigated. Successful three-dimensional micro structures were produced using PBW in GaAs and the simulation and experimental results are comparable which has helped to give a better understanding of the processes of PBW in GaAs and the subsequent electrochemical etching process. Keywords: Proton Beam Writing, Gallium Arsenide, SILVACO.