The Fabrication Of GaN HEMT Device Having Micro Structure

AlGaN/GaN HEMT is a research hotspot in high-pressure, high-frequency and high power devices areas. MEMS micro-structure is an important research direction of the high sensitivity sensor. GaN HEMT device and MEMS micro-structure have significant advantages. The combination of both has an important application prospect on power-electric conversion sensor field. The main study is preparation and process optimization of high-performance AlGaN / GaN HEMT devices, complete AlGaN / GaN membrane wet etching Preparation, finally obtained GaN HEMT devices on the membrane.The AlGaN/GaN membrane principle was simulated by ANSYS software. Maximum stress and stress change rate is located at the edge of micro membrane. This position has the maximum variation of the polarization effect. The HEMT device placed in the edge of the membrane can improve detection performance.Secondly, in order to improve the performance of AlGaN / Ga N HEMT devices, optimized device structure in some aspects: In order to reduce the difficulty of the electrode to clime the step after ICP isolate the active region, using positive resist as a mask to obtain tilt table; In order to improve the characteristics of the source-drain ohmic contact, using TLM model to test five kind of metal electrode structure. Comparison of different number,thickness and components of Ti/Al layer, chose the Ti/Al/Ti/Al/Ti/Al/Ni/Au structure as source and drain electrodes because it has the smallest contact resistance and best surface morphology. Improve gate Schottky contact characteristics can enhance the gate to enhance control of the channel. By annealing,the Schottky characteristics are significantly improved, the forward voltage increases, the reverse current is significantly reduced.Finally, researched the AlGaN / GaN micro membrane prepartion, Using wet etching process to etch Si substrate on the back of the wafer to form a cavity, etching clean the Si in the cavity, releasing the membrane.By comparing different etchant, find anisotropic etchant has a very slow etching rate, so we chosed sotropic etchant hydrofluoric acid, nitric acid etching solution that has a faster rate. Etching mask material need to be able to withstand hydrofluoric acid, nitric acid corrosion, gold and silicon nitride materials can not achieve requirement of the high corrosion depth, but paraffin material can withstand corrosion; After two major preparation process, the AlGaN / GaN HEMT device has been placed on the micro membrane, small distortion of the membrane can affect the current characteristics of the device, indicating the combination of the two have the potential to make force- electric conversion sensor.