基于PCL-CSL协同设计的1200 V沟槽型SiC MOSFET性能优化与栅氧电场分析
doi: 10.11999/JEIT260164 cstr: 32379.14.JEIT260164
Performance Optimization and Gate Oxide Electric Field Analysis of 1200V Trench SiC MOSFET Based on PCL-CSL Collaborative Design
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摘要: 碳化硅(SiC)功率金属-氧化物-半导体场效应晶体管(MOSFET)凭借耐压高、导通电阻低和功耗小的优势，已广泛应用于中高压电力电子系统中，在提升系统效率与功率密度方面具有重要意义。本文基于TCAD仿真平台，开展
1200 V等级沟槽型SiC MOSFET的结构设计与电学特性仿真研究。通过双侧P型柱(PCL)与电流扩展层(CSL)协同设计，有效优化了器件在阻断状态下的电场分布与导通状态下的电流输运性能。系统仿真分析了外延层掺杂浓度(NEpi)、沟槽宽度与深度、P型体区(PW)注入剂量、PCL间距及CSL注入剂量等关键结构参数对器件比导通电阻(Ron,sp)、阈值电压(VTH)、击穿电压(BV)及栅氧峰值电场(Eox-max)的影响机制。研究结果表明，优化后的器件可实现VTH=4.7 V、Ron,sp=1.57 mΩ·cm2、BV=1708 V、Eox-max=2.5 MV/cm的良好性能折衷。本研究为开发高性能沟槽型SiC MOSFET提供了系统的仿真方法与设计依据。Abstract:Objective SiC trench MOSFETs at 1200 V rating are widely recognized as key components in modern medium- and high-voltage power conversion systems due to their superior switching performance, low conduction loss, and high-temperature stability. However, conventional trench-based device structures suffer from severe electric field crowding at the trench corner and bottom gate oxide, which frequently causes the peak oxide electric field to exceed the safe operating limit of 3 MV/cm and seriously threatens long-term reliability. Moreover, significant performance trade-offs exist among breakdown voltage, specific on-resistance, threshold voltage, and gate oxide electric field, so it is difficult to achieve high efficiency and high robustness simultaneously. To overcome these bottlenecks, a synergistic structure combining deep P-type columns (PCL), Carrier Storage Layer (CSL), and locally thickened gate oxide is investigated in this work. The primary objective is to modulate the electric field distribution, suppress electric field concentration, improve carrier transport behavior, and realize a well-balanced device performance. This study aims to provide a systematic and practical design methodology for the development of high-reliability, high-performance1200 V SiC trench MOSFETs for industrial applications.Methods Numerical device simulations are systematically performed using the TCAD simulation platform to comprehensively analyze and optimize the electrical performance of 1200 V SiC trench MOSFETs. To ensure simulation results, a full set of advanced physical models is rigorously implemented, including bandgap narrowing, Shockley-Read-Hall (SRH) recombination, Auger recombination, impact ionization for avalanche breakdown, incomplete ionization of dopants, and high-field saturation mobility models accounting for velocity saturation and scattering effects. A device structure integrated with deep PCL, CSL, and locally thickened bottom gate oxide is constructed to suppress the gate oxide electric field and improve device reliability. Key structural and process parameters are systematically swept and quantitatively analyzed, including epitaxial layer thickness and doping concentration, trench width and depth, P-well implantation dose, PCL spacing, and CSL implantation dose. Static electrical characteristics, such as threshold voltage (Vth), specific on-resistance (Ron,sp), breakdown voltage (BV), and peak gate oxide electric field (Eox,max) are extracted and evaluated. The optimal parameter combination is finally determined through a comprehensive trade-off analysis between conduction performance and long-term device reliability, achieving a balanced performance for high-power applications.Results and Discussions Simulation results demonstrate that the deep PCL structure effectively redirects electric field lines away from the trench bottom gate oxide and significantly alleviates electric field crowding. Combined with locally thickened bottom gate oxide, the peak gate oxide electric field is reduced to below 3 MV/cm, which satisfies industrial reliability standards. The introduction of the CSL layer broadens the vertical conduction path, relieves current crowding, and effectively reduces specific on-resistance. Parameter optimization reveals that epitaxial conditions, trench dimensions, PW implantation doses and CSL implantation doses directly determine the trade-off between breakdown voltage and conduction performance ( Fig. 5 ,Fig. 6 ,Fig. 9 ,Fig. 10 ,Fig. 19 ), while PCL spacing exhibits a significant influence on electric field shielding (Fig. 16 ,Fig. 17 ). After multi-parameter optimization, the device achieves a threshold voltage of 4.7 V, a high breakdown voltage of1708 V, a low specific on-resistance of 1.57 mΩ·cm2, and a safe gate oxide peak field of 2.5 MV/cm (Table 2 ), demonstrating excellent overall performance suitable for high-voltage power applications.Conclusions A synergistic PCL-CSL structural design for 1200 V SiC trench MOSFETs is researched and validated through TCAD simulation. To address the inherent bottlenecks of conventional SiC trench MOSFETs, such as high gate oxide electric field, restricted breakdown capability and contradictory trade-off between on-state conduction loss and device reliability, the modulation mechanism of deep PCL and CSL is comprehensively explored. The influences of epitaxial layer thickness and doping level, trench dimensions, P-well implantation doses, PCL spacing, and CSL implantation doses on key electrical performance and gate oxide long-term reliability are systematically clarified and summarized through extensive parameter sweeping and comparative analysis.Under the collaborative optimization of multiple structural factors, the optimized device configuration achieves a superior comprehensive performance balance, including low specific on-resistance for reduced conduction loss, high and stable breakdown voltage for high-voltage endurance, reasonable threshold voltage for normal switching operation, and suppressed electric field concentration near the trench bottom oxide. Benefiting from the rational doping profile and structural arrangement, the peak gate oxide electric field is effectively limited and steadily controlled below the 3 MV/cm industrial safety threshold, which greatly prevents oxide degradation and guarantees stable and robust device operation under high-bias and harsh working conditions.The structural strategy and parameter optimization method provide valuable guidance for the design, simulation, and process development of high-voltage and high-reliability SiC power devices. This work contributes to the performance improvement of wide-bandgap semiconductor devices and promotes their industrial application in renewable energy systems, electric vehicles, and medium-voltage power supplies. -
表 1 沟槽型SiC MOSFET的主要结构参数以及性能参数
参数 数值 Cell宽度 2.8 μm EPI深度 12 μm EPI浓度 1×1016 cm–3 PCL掺杂 总剂量5×1014 cm–2，5步注入 PW掺杂 总剂量9.5×1012 cm–2，4步注入 CSL掺杂 总剂量5×1012 cm–2，5步注入 PW结深 0.7 µm Trench宽度 0.7 µm Trench深度 1.2 µm 侧壁氧化层厚度 50 nm 底部氧化层厚度 200 nm VTH 5.0 V Ron,sp 1.70 mΩ·cm2 BV 1712 VEox-max 2.6 MV/cm 
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表 2 器件关键结构参数以及主要性能参数
参数 数值 Cell宽度 2.8 μm EPI深度 12 μm EPI浓度 1×1016 cm–3 PCL掺杂 总剂量5×1014 cm–2，5步注入 PCL间距 1.0 μm PW掺杂 总剂量9.5×1012 cm–2，4步注入 CSL掺杂 总剂量5×1012 cm–2，5步注入 PW结深 0.7 μm Trench宽度 0.5 μm Trench深度 1.1 μm 侧壁氧化层厚度 50 nm 底部氧化层厚度 200 nm VTH 4.7 V Ron,sp 1.57 mΩ·cm2 BV 1708 VEox-max 2.5 MV/cm
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