Research On The Etching Process For The Manufacture Of P-GaN Gate High Electron Mobility Transistors

GaN material has a wide application prospect in power electronics and base station chips because of its advantages such as wide band gap,high saturation electron speed,high thermal conductivity and high temperature operation.Among them,GaN/AlGaN as the core of high electron mobility transistor（HEMT）has also been concerned.However,the current gate etching of normally closed devices is not perfect.To solve this problem,this paper mainly focuses on the etching process of P-GaN gate HEMT devices.First,the traditional inductively coupled plasma（ICP）BCl₃/SF₆/N₂ plasma etching GaN is studied.The results show that the selection ratio to AlGaN is increased to 59.5due to the addition of N₂,and the GaN etching is successfully stopped on AlGaN.The etched AlGaN has no grooves at the bottom and small surface roughness.By X-ray photoelectron spectroscopy（XPS）characterization,it was found that there were characteristic peaks of Ga F_X and Al F_Xon the surface of AlGaN after etching.It was speculated that the barrier layer formed by the sediment protected AlGaN from etching.Secondly,GaN etching by O₂/BCl₃ atom layer is studied.By adjusting the parameters of oxidation time,etching time,etching power and etching bias,the etching depth of each cycle is 1nm/cycle.By controlling the number of cycles,GaN is etched to stop on AlGaN.The etched AlGaN has no grooves at the bottom and small surface roughness.At the same time,atomic layer etching can deal with the problems of uniformity and micro-load effect after 10 nm technology node.Through XPS characterization,it is found that the oxide on GaN surface increases after plasma oxidation and decreases after etching.It is speculated that the basic etching process of the atomic layer is a process of O₂ plasma oxidation on GaN surface to form oxide and then remove oxide.Thirdly,the BCl₃/Ar atom layer etching GaN is studied.By adjusting the parameters of oxidation time,etching time,etching power and etching bias,the etching depth of each cycle is 0.74nm/cycle.Control the number of cycles by etching GaN to stop on the AlGaN.The etched AlGaN has no grooves at the bottom and small surface roughness.Based on the uniformity and micro-load effect after the 10 nm technology node,the etching depth of each cycle is shallower and the precision is higher.Through XPS characterization,it was found that the characteristic peak of Ga-Cl was only found in the chlorination step,but not in the initial and etched GaN surface.It can be speculated that the basic etching process of the atomic layer is a process of BCl₃ plasma chlorinating GaN surface to form chloride and then removing chloride.In order to solve the etching problem of P-GaN gate,three etching technologies are provided in this paper,and a scheme for the fabrication of P-GaN gate is provided.