Study On High Temperature Characteristics Of Au Wire Ball Bonding Of AlGaN/GaN HEMT Hemt Devices

GaN,as the third generation semiconductor material,has excellent physical properties.Compared with other semiconductor materials,GaN has excellent properties such as wide band gap,high electron saturation speed,high breakdown electric field and high electron mobility.It plays an important role in modern industrial fields such as semiconductor lighting,power electronic devices,lasers and detectors.With the wide application of GaN-based high electron mobility transistors,the lifetime and stability of devices are facing severe challenges in some harsh and severe environments.In high temperature environment,the reliability of device packaging is very important to ensure the performance and life of the device,the most critical step in the packaging process is wire bonding,wire bonding technology has become the main technology of chip interconnection because of its low cost,high reliability,high yield and other characteristics.In this paper,based on AlGaN/GaN HEMT devices,the technology of gold wire ball bonding was studied.after gold wire ball bonding with a purity of 99.99% and a diameter of 25?m,the devices were stored for 12 h at different temperatures.the bonding surface morphology,ohmic contact electrical characteristics and tensile test were carried out before and after storage,and the contact characteristics were further analyzed.Before gold wire ball bonding,the reliability of bonding electrode(PAD)was analyzed,and thermal evaporation and electron beam evaporation processes were carried out on ceramic and sapphire substrates respectively.When coating film by thermal evaporation method,it is not suitable for gold wire ball bonding because of its poor adhesion and low density of evaporated metal However,electron beam evaporation coating has the advantages of cleanness,smoothness and high density of evaporated metal,and has no defects in the bonding process and a high success rate.After the gold wire ball bonding of AlGaN/GaN HEMT devices was completed,high temperature tests were carried out at 200 ?,300 ?,400 ? and 500 ? for 12 h in air atmosphere.The experimental results show that with the increase of storage temperature,defects such as voids,cracks and uneven bonding electrode(PAD)surface gradually appear on the bonding surface.Although the resistance between two bonding contact points decreases,these defects are accompanied by the decrease of bonding strength.The change of surface morphology of gold wire ball bonding may be caused by the influence of temperature on the internal stress of bonding wire,and the decrease of resistance between two bonding contact points may be caused by the mutual diffusion and re-alloying between different metal layers of ohmic contact electrode caused by high temperature treatment.Therefore,on the premise of ensuring bonding strength,high temperature treatment is beneficial to improve the electrical characteristics of bonding electrodes.