Performance Limit and Design Guideline of 4H-SiC Superjunction Devices Considering Anisotropy of Impact Ionization
Changwang Wang, Xuan Li, Lingfeng Li, Xiaochuan Deng, Wentong Zhang, Zheng Liu, Yansheng Zou, Weining Qian, Zhaoji Li, Bo Zhang
Abstract
Superjunction (SJ) structure is one of the most effective approaches to improving the performance limit between specific ON-resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,sp}}$ </tex-math></inline-formula> ) and breakdown voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}$ </tex-math></inline-formula> ) for the unipolar power device, particularly in high-voltage and high-current areas. In this letter, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,sp}}-\textit {BV}$ </tex-math></inline-formula> performance limit of 4H-SiC SJ drift region is achieved featuring both the two-dimensional electric field and the anisotropy of impact ionization of 4H-SiC. The breakdown path is the curve from the bottom midpoint of N pillar to the top midpoint of P pillar via the midpoint of P-N pillar interface, instead of the midline of the pillar, due to that the impact ionization along [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11~\overline {{2}}~0$ </tex-math></inline-formula> ] is stronger than that along [0001]. Moreover, a design guideline is provided for optimized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,sp}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,opt}}$ </tex-math></inline-formula> ) under a given <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}$ </tex-math></inline-formula> , including the width, depth, and concentration of SiC SJ drift region. SJ adoption enables SiC drift region to have a quasi-linear dependence of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,sp}}$ </tex-math></inline-formula> on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}$ </tex-math></inline-formula> , i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,sp}}\propto \textit {BV}^{{1.007}}$ </tex-math></inline-formula> , which is well verified by TCAD simulation. With <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}$ </tex-math></inline-formula> larger than 2000V, the SJ utilization can significantly reduce <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on,sp}}$ </tex-math></inline-formula> of SiC device. By determining the breakdown path, the theoretical performance limit shows huge potential of SJ approach for the high-voltage and high-current SiC device, and the practical design guideline can instruct to better design the SiC SJ device.