垂直结构氮化镓功率晶体管的材料与工艺问题
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摘要
硅功率器件已接近其理论物理性能的极限。基于宽禁带半导体材料的电力电子系统能够实现更高的功率密度和电能转换效率,而具有高临界电场和载流子迁移率的氮化镓被认为是未来高功率、高频和高温应用的最有希望的候选者之一,而由品质因子给出的氮化镓基功率器件的综合性能具有大于1 000倍于硅器件的理论极限。目前已产业化的氮化镓功率晶体管主要基于水平结构,但垂直结构更有利于实现更高电压和更大电流。随着氮化镓衬底材料的逐渐成熟,近期垂直结构氮化镓功率器件成为了学术界和产业界的研究热点,并被认为是下一代650～3 300 V电力电子应用的候选器件。基于此,回顾了垂直结构氮化镓晶体管的最新进展,特别是与器件相关的材料和工艺问题,并总结了开发高性能垂直结构氮化镓功率晶体管的主要挑战。
Silicon-based power devices are reaching their fundamental performance limit. The use of wide-bandgap semiconductors offers potential for power electronic systems with much higher power densities and higher conversion efficiency. Gallium nitride(GaN), with a high critical electric field and carrier mobility, is considered as one of the most promising candidates for the future high-power, high-frequency and high-temperature applications. The comprehensive performance of GaN-based power devices given by the quality factor is 1000 times of the theoretical limit of Si-based devices. At present, the industrialized GaN power transistors are primarily based on lateral structures, however, the vertical structures are more suitable for the realization of even higher voltage and larger current. Particularly, vertical GaN power devices have recently attracted increasing attention from academia and industrial cycles along with the gradual maturation of GaN substrate materials, and they are considered as candidates for applications of the nextgeneration 650～3 300 V power electronics. In this background, this paper reviews recent progress and the key remaining challenges towards the development of vertical GaN power transistors, with emphasis on the materials and processing issues related to each device architecture.
Silicon-based power devices are reaching their fundamental performance limit. The use of wide-bandgap semiconductors offers potential for power electronic systems with much higher power densities and higher conversion efficiency. Gallium nitride(GaN), with a high critical electric field and carrier mobility, is considered as one of the most promising candidates for the future high-power, high-frequency and high-temperature applications. The comprehensive performance of GaN-based power devices given by the quality factor is 1000 times of the theoretical limit of Si-based devices. At present, the industrialized GaN power transistors are primarily based on lateral structures, however, the vertical structures are more suitable for the realization of even higher voltage and larger current. Particularly, vertical GaN power devices have recently attracted increasing attention from academia and industrial cycles along with the gradual maturation of GaN substrate materials, and they are considered as candidates for applications of the nextgeneration 650～3 300 V power electronics. In this background, this paper reviews recent progress and the key remaining challenges towards the development of vertical GaN power transistors, with emphasis on the materials and processing issues related to each device architecture.
引文
[1]Ohta1 H,Hayashi1 K,Horikiri F,et al.5.0 kV breakdown-voltage vertical GaN p-n junction diodes[J].Japanese Journal of Applied Physics,2018,57(4S):04FG09.
[2]Nie Hui,Diduck Q,Alvarez B,et al.1.5-kV and 2.2-mΩ-cm2Vertical GaN Transistors on Bulk-GaN substrates[J].IEEE Electron Device Letters,2014,35(9):939-941.
[3]Dong Ji,Chowdhury S.Design of 1.2 kV power switches with low RON using GaN-based vertical JFET[J].IEEE Transactions on Electron Devices,2015,62(8):2571-2578.
[4]Zhang Yuhao,Sun Min,Perozek J,et al.Large area 1.2 kVGaN vertical power FinFETs with a record switching figureof-merit[J].IEEE Electron Device Letters,2018,40(1):75-78.
[5]Liu Chao,Abdul K R,Matioli E.GaN-on-Si quasivertical power MOSFETs[J].IEEE Electron Device Letters,2018,39(1):71-74.
[6]Geng Huiyuan,Sunakawa H,Sumi N,et al.Growth and strain characterization of high quality GaN crystal by HV-PE[J].Journal of Crystal Growth,2012,350(1):44-49.
[7]Oshima Y,Yoshida T,Eri T,et al.Freestanding GaN wafers by hydride vapor phase epitaxy using void-assisted separation technology[J].Technology of Gallium Nitride Crystal Growth,2010,133:79-96.
[8]Paskova T,Hanser D A,Evans K R.GaN substrates forⅢnitride devices[J].Proceedings of the IEEE,2010,98(7):1324-1338.
[9]Motoki K.Development of gallium nitride substrates[J].SEITechnical Review,2010,70:28-35.
[10]Otoki Y,Tanaka T,Kamogawa H,et al.Impact of crystalquality improvement of epitaxial wafers on RF and power switching devices by utilizing VAS-method grown GaNsubstrates with low-density and uniformly distributed dislocations[C].CS MANTECH Conference,Indian Wells,California,2013:109-112.
[11]Kizilyalli I C,Edwards A P,Aktas O,et al.Vertical power p-n diodes based on bulk GaN[J].IEEE Transactions on Electron Devices,2015,62(2):414-422.
[12]Baliga B J.Fundamentals of Power Semiconductor Devices[M].Berlin:Springer Science&Business Media,2010.
[13]Tanaka T,Kaneda N,Mishima T,et al.Roles of lightly doped carbon in the drift layers of vertical n-GaN Schottky diode structures on freestanding GaN substrates[J].Japanese Journal of Applied Physics,2015,54(4):041002.
[14]Kizilyalli I C,Prunty T,Aktas O.4-kV and 2.8-mΩ-cm2vertical GaN p-n diodes with low leakage currents[J].IEEEElectron Device Letters,2015,36(10):1073-1075.
[15]Feng Gan,Suda J,Kimoto T.Space-modulated junction termination extension for ultrahigh-voltage p-i-n diodes in 4H-SiC[J].IEEE Transactions on Electron Devices,2012,59(2):414-418.
[16]Mahajan A,Skromme B J.Design and optimization of junction termination extension(JTE)for 4H-SiC high voltage Schottky diodes[J].Solid-State Electronics,2005,49(6):945-955.
[17]Feigelson B N,Anderson T J,Abraham M,et al.Multicycle rapid thermal annealing technique and its application for the electrical activation of Mg implanted in GaN[J].Journal of Crystal Growth,2012,350(1):21-26.
[18]Greenlee J D,Feigelson B N,Anderson T J,et al.Symmetric multicycle rapid thermal annealing:enhanced activation of implanted dopants in GaN[J].ECS Journal of Solid State Science and Technology,2015,4(9):382-386.
[19]Jain S C,Willander M,Narayan J,et al.III-nitrides:Growth,characterization,and properties[J].Journal of Applied Physics,2000,87(3):965-1006.
[20]Tadjer M J,Feigelsona B N,Greenlee J D,et al.Selective p-type Doping of GaN:Si by Mg Ion implantation and multicycle rapid thermal annealing[J].Ecs Journal of Solid State Science and Technology,2016,5(2):124-127.
[21]Kub F J,Eddy C R,Hite J K,et al.Activation of Mg implanted in GaN by multicycle rapid thermal annealing[J].Electronics Letters,2014,50(3):197-198.
[22]Zhang Yuhao,Liu Zhihong,Tadjer M J,et al.Vertical GaNjunction barrier schottky rectifiers by selective ion implantation[J].IEEE Electron Device Letters,2017,38(8):1097-1100.
[23]Ben-Yaacov I.AlGaN/GaN current aperture vertical electron transistors with regrown channels[J].Journal of Applied Physics,2004,95(4):2073-2078.
[24]Chowdhury S,Wong M H,Swenson B L,et al.CAVET on bulk GaN substrates achieved with MBE-Regrown AlGaN/GaN layers to suppress dispersion[J].IEEE Electron Device Letters,2012,33(1):41-43.
[25]Chowdhury S,Swenson B L,Mishra U K.Enhancement and depletion mode AlGaN/GaN CAVET with Mg-Ion-implanted GaN as current blocking layer[J].IEEE Electron Device Letters,2008,29(6):543-545.
[26]Shibata D,Kajitani R,Ogawa M,et al.1.7 kV/1.0 mΩ-cm2normally-off vertical GaN transistor on GaN substrate with regrown p-GaN/AlGaN/GaN semipolar gate structure[C].2016 IEEE International Electron Devices Meeting(IED-M).San Francisco,California,2016:10.1.1-10.1.4.
[27]Gupta C,Lund C,Chan S H,et al.In-situ oxide,GaN interlayer based vertical trench MOSFET(OG-FET)on bulk GaN substrates[J].IEEE Electron Device Letters,2017,38(3):353-355.
[28]Li R,Cao Yu,Chen M,et al.600 V/1.7ΩNormally-Off GaN vertical trench metal-oxide-semiconductor field-effect transistor[J].IEEE Electron Device Letters,2016,37(11):1466-1469.
[29]Zhang Yuhao,Sun Min,Liu Zhihong,et al.Trench formation and corner rounding in vertical GaN power devices[J].Applied Physics Letters,2017,110(19):193506.
[30]Itoh M,Kinoshita T,Koike C,et al.Straight and smooth etching of GaN(1-100)plane by combination of reactive ion etching and KOH wet etching techniques[J].Japanese Journal of Applied Physics,2006,45(5A):3988-3991.
[31]Kodama M,Sugimoto M,Hayashi E,et al.GaN-based trench gate metal oxide Semiconductor field-effect transistor fabricated with novel wet etching[J].Applied Physics Express,2008,1(2):021104.
[32]Oka T,Ina T,Nishii J,et al.1.8 mΩ-cm2vertical GaN-based trench metal-oxide-semiconductor field-effect transistors on a free-standing GaN substrate for 1.2 kV-class operation[J].Applied Physics Express,2015,8(5):021002.
[33]Otake H,Chikamatsu K,Yamaguchi A,et al.Vertical GaN-based trench gate metal oxide semiconductor field-effect transistors on GaN bulk substrates[J].Applied Physics Express,2008,1(1):155-162.
[34]Oka T,Ina T,Ueno Y,et al.Over 10 an operation with switching characteristics of 1.2 kV-class vertical GaN trench MOSFETs on a bulk GaN substrate[C]//2016 28th In-ternational Symposium on Power Semiconductor Devices and ICs(ISPSD).Prague,Czech Republic,2016:459-462.
[35]Gupta C,Lund C,Chan S H,et al.OG-FET:An in-situ oxide,GaN interlayer-based vertical trench MOSFET[J].IEEE Electron Device Letters,2016,37(12):1601-1604.
[36]Sun Min,Zhang Yuhao,Gao Xiang,et al.High-performance GaN vertical fin power transistors on bulk GaN substrates[J].IEEE Electron Device Letters,2017,38(4):509-512.
[37]Zhang Yuhao,Sun Min,Wong H,et al.,Origin and control of off-state leakage current in GaN-on-Si vertical diodes[J].IEEE Transactions on Electron Devices,2015,62(7):2155-2161.
[38]Zhang Yuhao,Sun Min,Piedra D,et al.1 200 V GaN vertical Fin power field-effect transistors[C]//2017 IEEE In-ternational Electron Devices Meeting(IEDM).San Francisco,California,2017:9.2.1-9.2.4.
[2]Nie Hui,Diduck Q,Alvarez B,et al.1.5-kV and 2.2-mΩ-cm2Vertical GaN Transistors on Bulk-GaN substrates[J].IEEE Electron Device Letters,2014,35(9):939-941.
[3]Dong Ji,Chowdhury S.Design of 1.2 kV power switches with low RON using GaN-based vertical JFET[J].IEEE Transactions on Electron Devices,2015,62(8):2571-2578.
[4]Zhang Yuhao,Sun Min,Perozek J,et al.Large area 1.2 kVGaN vertical power FinFETs with a record switching figureof-merit[J].IEEE Electron Device Letters,2018,40(1):75-78.
[5]Liu Chao,Abdul K R,Matioli E.GaN-on-Si quasivertical power MOSFETs[J].IEEE Electron Device Letters,2018,39(1):71-74.
[6]Geng Huiyuan,Sunakawa H,Sumi N,et al.Growth and strain characterization of high quality GaN crystal by HV-PE[J].Journal of Crystal Growth,2012,350(1):44-49.
[7]Oshima Y,Yoshida T,Eri T,et al.Freestanding GaN wafers by hydride vapor phase epitaxy using void-assisted separation technology[J].Technology of Gallium Nitride Crystal Growth,2010,133:79-96.
[8]Paskova T,Hanser D A,Evans K R.GaN substrates forⅢnitride devices[J].Proceedings of the IEEE,2010,98(7):1324-1338.
[9]Motoki K.Development of gallium nitride substrates[J].SEITechnical Review,2010,70:28-35.
[10]Otoki Y,Tanaka T,Kamogawa H,et al.Impact of crystalquality improvement of epitaxial wafers on RF and power switching devices by utilizing VAS-method grown GaNsubstrates with low-density and uniformly distributed dislocations[C].CS MANTECH Conference,Indian Wells,California,2013:109-112.
[11]Kizilyalli I C,Edwards A P,Aktas O,et al.Vertical power p-n diodes based on bulk GaN[J].IEEE Transactions on Electron Devices,2015,62(2):414-422.
[12]Baliga B J.Fundamentals of Power Semiconductor Devices[M].Berlin:Springer Science&Business Media,2010.
[13]Tanaka T,Kaneda N,Mishima T,et al.Roles of lightly doped carbon in the drift layers of vertical n-GaN Schottky diode structures on freestanding GaN substrates[J].Japanese Journal of Applied Physics,2015,54(4):041002.
[14]Kizilyalli I C,Prunty T,Aktas O.4-kV and 2.8-mΩ-cm2vertical GaN p-n diodes with low leakage currents[J].IEEEElectron Device Letters,2015,36(10):1073-1075.
[15]Feng Gan,Suda J,Kimoto T.Space-modulated junction termination extension for ultrahigh-voltage p-i-n diodes in 4H-SiC[J].IEEE Transactions on Electron Devices,2012,59(2):414-418.
[16]Mahajan A,Skromme B J.Design and optimization of junction termination extension(JTE)for 4H-SiC high voltage Schottky diodes[J].Solid-State Electronics,2005,49(6):945-955.
[17]Feigelson B N,Anderson T J,Abraham M,et al.Multicycle rapid thermal annealing technique and its application for the electrical activation of Mg implanted in GaN[J].Journal of Crystal Growth,2012,350(1):21-26.
[18]Greenlee J D,Feigelson B N,Anderson T J,et al.Symmetric multicycle rapid thermal annealing:enhanced activation of implanted dopants in GaN[J].ECS Journal of Solid State Science and Technology,2015,4(9):382-386.
[19]Jain S C,Willander M,Narayan J,et al.III-nitrides:Growth,characterization,and properties[J].Journal of Applied Physics,2000,87(3):965-1006.
[20]Tadjer M J,Feigelsona B N,Greenlee J D,et al.Selective p-type Doping of GaN:Si by Mg Ion implantation and multicycle rapid thermal annealing[J].Ecs Journal of Solid State Science and Technology,2016,5(2):124-127.
[21]Kub F J,Eddy C R,Hite J K,et al.Activation of Mg implanted in GaN by multicycle rapid thermal annealing[J].Electronics Letters,2014,50(3):197-198.
[22]Zhang Yuhao,Liu Zhihong,Tadjer M J,et al.Vertical GaNjunction barrier schottky rectifiers by selective ion implantation[J].IEEE Electron Device Letters,2017,38(8):1097-1100.
[23]Ben-Yaacov I.AlGaN/GaN current aperture vertical electron transistors with regrown channels[J].Journal of Applied Physics,2004,95(4):2073-2078.
[24]Chowdhury S,Wong M H,Swenson B L,et al.CAVET on bulk GaN substrates achieved with MBE-Regrown AlGaN/GaN layers to suppress dispersion[J].IEEE Electron Device Letters,2012,33(1):41-43.
[25]Chowdhury S,Swenson B L,Mishra U K.Enhancement and depletion mode AlGaN/GaN CAVET with Mg-Ion-implanted GaN as current blocking layer[J].IEEE Electron Device Letters,2008,29(6):543-545.
[26]Shibata D,Kajitani R,Ogawa M,et al.1.7 kV/1.0 mΩ-cm2normally-off vertical GaN transistor on GaN substrate with regrown p-GaN/AlGaN/GaN semipolar gate structure[C].2016 IEEE International Electron Devices Meeting(IED-M).San Francisco,California,2016:10.1.1-10.1.4.
[27]Gupta C,Lund C,Chan S H,et al.In-situ oxide,GaN interlayer based vertical trench MOSFET(OG-FET)on bulk GaN substrates[J].IEEE Electron Device Letters,2017,38(3):353-355.
[28]Li R,Cao Yu,Chen M,et al.600 V/1.7ΩNormally-Off GaN vertical trench metal-oxide-semiconductor field-effect transistor[J].IEEE Electron Device Letters,2016,37(11):1466-1469.
[29]Zhang Yuhao,Sun Min,Liu Zhihong,et al.Trench formation and corner rounding in vertical GaN power devices[J].Applied Physics Letters,2017,110(19):193506.
[30]Itoh M,Kinoshita T,Koike C,et al.Straight and smooth etching of GaN(1-100)plane by combination of reactive ion etching and KOH wet etching techniques[J].Japanese Journal of Applied Physics,2006,45(5A):3988-3991.
[31]Kodama M,Sugimoto M,Hayashi E,et al.GaN-based trench gate metal oxide Semiconductor field-effect transistor fabricated with novel wet etching[J].Applied Physics Express,2008,1(2):021104.
[32]Oka T,Ina T,Nishii J,et al.1.8 mΩ-cm2vertical GaN-based trench metal-oxide-semiconductor field-effect transistors on a free-standing GaN substrate for 1.2 kV-class operation[J].Applied Physics Express,2015,8(5):021002.
[33]Otake H,Chikamatsu K,Yamaguchi A,et al.Vertical GaN-based trench gate metal oxide semiconductor field-effect transistors on GaN bulk substrates[J].Applied Physics Express,2008,1(1):155-162.
[34]Oka T,Ina T,Ueno Y,et al.Over 10 an operation with switching characteristics of 1.2 kV-class vertical GaN trench MOSFETs on a bulk GaN substrate[C]//2016 28th In-ternational Symposium on Power Semiconductor Devices and ICs(ISPSD).Prague,Czech Republic,2016:459-462.
[35]Gupta C,Lund C,Chan S H,et al.OG-FET:An in-situ oxide,GaN interlayer-based vertical trench MOSFET[J].IEEE Electron Device Letters,2016,37(12):1601-1604.
[36]Sun Min,Zhang Yuhao,Gao Xiang,et al.High-performance GaN vertical fin power transistors on bulk GaN substrates[J].IEEE Electron Device Letters,2017,38(4):509-512.
[37]Zhang Yuhao,Sun Min,Wong H,et al.,Origin and control of off-state leakage current in GaN-on-Si vertical diodes[J].IEEE Transactions on Electron Devices,2015,62(7):2155-2161.
[38]Zhang Yuhao,Sun Min,Piedra D,et al.1 200 V GaN vertical Fin power field-effect transistors[C]//2017 IEEE In-ternational Electron Devices Meeting(IEDM).San Francisco,California,2017:9.2.1-9.2.4.