The Institute of Microelectronics has made important progress in studying the threshold voltage instability mechanism of GaN-based MIS-HEMT devices
Source: Huang Sen, High Frequency and High Voltage Center Release time: 2024-06-11Recently, the GaN power electronic device research and development team of the High Frequency and High Voltage Center of the Institute of Microelectronics, together with the Hong Kong University of Science and Technology, Peking University and Xidian University, published a review article titled "Threshold voltage instability in III-nitride heterostructure metal-insulator-semiconductor high-electron-mobility transistors : Characterization and interface engineering " in Applied Physics Reviews, an international authoritative journal in the field of applied physics. This work uses advanced interface state and body defect characterization methods to reveal the physical mechanism of threshold voltage instability of GaN-based heterojunction power devices. Aiming at the dynamic instability problem of GaN-based MIS-HEMT based on two common gate/passivation dielectrics, Al2O3 and SiNx , an innovative process that effectively suppresses surface interface states and dielectric defect states has been developed, which has promoted the development of the next generation of high-reliability GaN-based insulated gate power devices.
Compared with traditional semiconductor materials such as Si, GaN-based MIS/MOS-HEMT power devices based on metal-insulator-semiconductor (MIS) or metal-oxide-semiconductor (MOS) gate structures can operate at higher voltages, higher frequencies and higher temperatures, and have broad application prospects in high-efficiency power conversion, RF power amplifiers and extreme environment electronics. However, due to factors such as natural oxidation and process contamination, the surface of GaN materials easily loses the step flow morphology of the original fresh surface, thereby inducing a high-density surface state on GaN, leading to reliability problems such as current collapse of GaN-based power devices. On the other hand, in MIS/MOS structure power devices, there are also a large number of body defects in the gate dielectric and AlGaN/GaN heterostructures. Once these defect states, especially the gate dielectric defect states, are filled, it is difficult to release, resulting in more serious threshold voltage instability problems.
Based on first principles and surface physical and chemical analysis, the research team found that the shallow energy level interface states of GaN mainly originate from the strong interaction between Ga dangling bonds and atoms near its interface (ACS AMI, 10, 21721, 2018 & 13, 7725, 2021), while the deep energy level interface states are mainly related to the amorphous Ga2O chemical state on the surface , and its cracking temperature is above 450°C. Based on this , the research team innovatively proposed the "high-temperature remote plasma pretreatment (RPP)" method, which achieved the stable reproduction of atomic steps on the GaN surface with different surface conditions. The new "high-temperature RPP" method reduced the deep energy level interface state density of oxide/GaN represented by Al2O3 and nitride/GaN represented by SiNx by at least one order of magnitude. Among them, the SiNx / GaN interface state density has a minimum value of 1.5×1010eV-1cm-2 in the wide energy level range of 30meV-0.9eV , which is close to the optimal level of Si-based MOS devices. In order to characterize the gate interface state/body defects of GaN-based MIS-HEMT devices, the research team innovatively developed multiple modes of deep energy level transient spectroscopy (DLTS) rapid characterization methods such as "isothermal capture" and "constant capacitance", realizing the metal/insulator/AlGaN/GaN "multi-heterogeneous interface" The effective separation of body defects and interface states in heterojunction power devices reveals the correlation mechanism between dynamic on-resistance degradation, threshold voltage instability and interface/dielectric process of GaN-based MIS-HEMT power devices, providing important physical feedback for the reinforcement of the next generation of high-reliability GaN-based insulated gate power devices.
Compared with traditional semiconductor materials such as Si, GaN-based MIS/MOS-HEMT power devices based on metal-insulator-semiconductor (MIS) or metal-oxide-semiconductor (MOS) gate structures can operate at higher voltages, higher frequencies and higher temperatures, and have broad application prospects in high-efficiency power conversion, RF power amplifiers and extreme environment electronics. However, due to factors such as natural oxidation and process contamination, the surface of GaN materials easily loses the step flow morphology of the original fresh surface, thereby inducing a high-density surface state on GaN, leading to reliability problems such as current collapse of GaN-based power devices. On the other hand, in MIS/MOS structure power devices, there are also a large number of body defects in the gate dielectric and AlGaN/GaN heterostructures. Once these defect states, especially the gate dielectric defect states, are filled, it is difficult to release, resulting in more serious threshold voltage instability problems.
Based on first principles and surface physical and chemical analysis, the research team found that the shallow energy level interface states of GaN mainly originate from the strong interaction between Ga dangling bonds and atoms near its interface (ACS AMI, 10, 21721, 2018 & 13, 7725, 2021), while the deep energy level interface states are mainly related to the amorphous Ga2O chemical state on the surface , and its cracking temperature is above 450°C. Based on this , the research team innovatively proposed the "high-temperature remote plasma pretreatment (RPP)" method, which achieved the stable reproduction of atomic steps on the GaN surface with different surface conditions. The new "high-temperature RPP" method reduced the deep energy level interface state density of oxide/GaN represented by Al2O3 and nitride/GaN represented by SiNx by at least one order of magnitude. Among them, the SiNx / GaN interface state density has a minimum value of 1.5×1010eV-1cm-2 in the wide energy level range of 30meV-0.9eV , which is close to the optimal level of Si-based MOS devices. In order to characterize the gate interface state/body defects of GaN-based MIS-HEMT devices, the research team innovatively developed multiple modes of deep energy level transient spectroscopy (DLTS) rapid characterization methods such as "isothermal capture" and "constant capacitance", realizing the metal/insulator/AlGaN/GaN "multi-heterogeneous interface" The effective separation of body defects and interface states in heterojunction power devices reveals the correlation mechanism between dynamic on-resistance degradation, threshold voltage instability and interface/dielectric process of GaN-based MIS-HEMT power devices, providing important physical feedback for the reinforcement of the next generation of high-reliability GaN-based insulated gate power devices.
