Design of Gradient Oxide-Bypassed Superjunction Power MOSFET Devices

The superjunction MOSFET power devices, such as p-n column superjunction (named SJ or CoolMOS) devices and oxide-bypassed (OB) devices, are highly recognized for their higher blocking capability and lower on-state resistance. However, the performance of SJ devices is greatly handicapped due to difficulties in formation of perfect charge-balanced SJ p-n columns by the current process technology, especially for devices with small widths and voltage ratings below 180 V. OB devices can be an alternative in this voltage region, which utilize the well established oxide thickness control in fabrication instead of the difficult doping control as in SJ devices. However, OB drift region electric field distribution is not as optimal as that in SJ devices. Gradient oxide-bypassed (GOB) structure enhances the performance of OB devices so that it can achieve a performance comparable to that of an ideal p-n column SJ device in the medium voltage range, and at the same time, requires simple process technology. Complete descriptions on the GOB device and related design issues are presented in this paper. Fabrication issues are also discussed with possible sacrificial materials and etchants for making the vertical graded oxide sidewalls. Design cases for 80, 120, and 180 V GOB devices are also illustrated for better understanding in the device.

[1]  D. W. Rice,et al.  Tapered windows in phosphorus-doped SiO 2 by ion implantation , 1978 .

[2]  K. R. Williams,et al.  Etch rates for micromachining processing-Part II , 2003 .

[3]  K. R. Williams,et al.  Etch rates for micromachining processing , 1996 .

[4]  G. Deboy,et al.  COOLMOS/sup TM/-a new milestone in high voltage power MOS , 1999, 11th International Symposium on Power Semiconductor Devices and ICs. ISPSD'99 Proceedings (Cat. No.99CH36312).

[5]  Y.C. Liang,et al.  Oxide-bypassed VDMOS (OBVDMOS): an alternative to superjunction high voltage MOS power devices , 2001, IEEE Electron Device Letters.

[6]  Y.C. Liang,et al.  Tunable oxide-bypassed trench gate MOSFET: breaking the ideal superjunction MOSFET performance line at equal column width , 2003, IEEE Electron Device Letters.

[7]  Young-Se Kwon,et al.  Graded etching of thermal oxide with various angles using silicafilm , 1980 .

[8]  Yung C. Liang,et al.  Practical superjunction MOSFET device performance under given process thermal cycles , 2004 .

[9]  Chenming Hu.  A parametric study of power MOSFETs , 1979, 1979 IEEE Power Electronics Specialists Conference.

[10]  Y.C. Liang,et al.  A simple technology for superjunction device fabrication: polyflanked VDMOSFET , 2002, IEEE Electron Device Letters.

[11]  Correction to "Optimization of the specific on-resistance of the COOLMOS/sup TM/" , 2001 .

[12]  Bantval J. Baliga,et al.  A low forward drop high voltage trench MOS barrier Schottky rectifier with linearly graded doping profile , 1998, Proceedings of the 10th International Symposium on Power Semiconductor Devices and ICs. ISPSD'98 (IEEE Cat. No.98CH36212).

[13]  Yung C. Liang,et al.  Theoretical Analyses of Oxide-Bypassed Superjunction Power Metal Oxide Semiconductor Field Effect Transistor Devices , 2005 .

[14]  Robert J. Deri,et al.  Dynamic etch mask technique for fabricating tapered semiconductor optical waveguides and other structures , 1990 .

[15]  T. Fujihira.  Theory of Semiconductor Superjunction Devices , 1997 .

[16]  Gary M. Dolny,et al.  Analysis of the effect of charge imbalance on the static and dynamic characteristics of the super junction MOSFET , 1999, 11th International Symposium on Power Semiconductor Devices and ICs. ISPSD'99 Proceedings (Cat. No.99CH36312).