Performance Limit and Design Guideline of 4H-SiC Superjunction Devices Considering Anisotropy of Impact Ionization

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.