金刚石散热衬底在GaN基功率器件中的应用进展

Application Progress of Diamond Heat Dissipation Substrate in GaN-based Power Devices

氮化镓(GaN)基功率器件性能的充分发挥受到沉积GaN的衬底低热导率的限制,具有高热导率的化学气相沉积(CVD)金刚石,成为GaN功率器件热扩散衬底材料的优良选择。相关学者在高导热金刚石与GaN器件结合技术方面开展了多项技术研究,主要包括低温键合技术、GaN外延层背面直接生长金刚石的衬底转移技术、单晶金刚石外延GaN技术和高导热金刚石钝化层散热技术。对GaN功率器件散热瓶颈的原因进行了详细评述,并对上述各项技术的优缺点进行了系统分析和评述,揭示了各类散热技术的热设计工艺开发和面临的技术挑战,并认为低温键合技术具有制备温度低、金刚石衬底导热性能可控的优势,但是大尺寸金刚石衬底的高精度加工和较差的界面结合强度对低温键合技术提出挑战。GaN外延层背面直接生长金刚石则具有良好的界面结合强度,但是涉及到高温、晶圆应力大、界面热阻高等技术难点。单晶金刚石外延GaN技术和高导热金刚石钝化层散热技术则分别受到单晶金刚石尺寸小、成本高和工艺不兼容的限制。因此,开发低成本大尺寸金刚石衬底,提高晶圆应力控制技术和界面结合强度,降低界面热阻,提高金刚石衬底GaN器件性能方面,将是未来金刚石与GaN器件结合技术发展的重点。

The full realization of superior properties of gallium nitride(GaN)-based power devices is limited by the low thermal conductivity of substrates,so the diamond with the highest thermal conductivity becomes an excellent heat dissipation substrate for GaN.Relevant scholars have carried out a lot of research on the combination of high thermal conductivity diamond and GaN devices,including low-temperature bonding technology,substrate transfer technology for directly growing diamond on the back of GaN epitaxial layer,single crystal diamond epitaxial GaN technology and heat dissipation technology for high thermal conductivity diamond passivation layer technology.The reasons of thermal bottleneck for GaN power devices were discussed in detail,and the advantages and disadvantages of these technologies were analyzed and reviewed systematically.The thermal design process development and challenges of various heat dissipation technologies were revealed.The low-temperature bonding technology had the advantages of low temperature and controllable quality of diamond substrate.However,the low-temperature bonding technology had challenges in the high-precision processing and low interface bonding force of large-size diamond films.The diamond directly growing on back of GaN epitaxial layer had excellent interface bonding strength,but technical difficulties were involved such as high temperature,high stress of wafer,and high thermal boundary resistance.The GaN epitaxial technology on single crystal diamond and high thermal conductivity diamond passivation layer technology were limited by the small size of the single crystal diamond wafer,high cost and incompatible process,respectively.Therefore,the development of diamond substrate with low cost and large size,the improvement of stress control of wafer and high interface bonding strength,the reduction of low thermal boundary resistance of GaN/diamond and the enhancement of the performance of GaN-on-diamond devices will be the focus of future development for GaN-on-diamond devices technology.