Experiments of a Novel Low-Voltage LDMOS With Ultrashallow Low-Resistance Path Modulated by Bulk Superjunction
Sen Zhang, Liang Song, Teng Liu, Huajun Jin, Yongshun Li, Nailong He, Weifeng Sun
Abstract
A novel low-voltage LDMOS with ultrashallow low-resistance path (ULP) modulated by the bulk superjunction (SJ) is proposed and experimentally demonstrated in this article. The new device features a highly doped surface ULP structure that acts as a low-resistance current path directly connecting the source and drain in the ON-state and is fully depleted by a step tungsten plug field plate (TP-FP) in the OFF-state. A charge-balanced SJ is further introduced in the bulk of the ULP LDMOS to modulate the bulk field, thereby improving the safe operating area (SOA). Experimental results have demonstrated that the ULP LDMOS has achieved a ULP with an injection depth of 100 nm and a short channel length of 150 nm, with a measured 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">${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ </tex-math></inline-formula> of only 7.07 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega \cdot $ </tex-math></inline-formula> mm2 under a 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">${V}_{\text {B}}$ </tex-math></inline-formula> of 41 V. This represents a reduction of 21.1% compared with the “silicon limit.” In addition, the TP-FP reduces the gate charge <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {g}}$ </tex-math></inline-formula> by 43.5% when compared with that of the conventional devices, achieving the best reported FOM = <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}} \cdot {Q}_{\text {g}}$ </tex-math></inline-formula> characteristics.