Simulation creates safer power devices
Recent years have seen an increasing need for automotive analogue and power devices with fully isolated N channel LDMOS and high BVnb, especially devices supporting voltages of 40V and over. Achieving a higher BVnb has until now required a trade-off with the Human Body Model (HBM) robustness for safety, and achieving both has required a bigger die in order to electrically isolate substrates. As the HBM robustness is a parameter that is difficult to estimate without actually fabricating devices, a new way to estimate HBM robustness was needed.
So the researchers used 2D TCAD simulations of numerous parameters and found that current flow concentration, which corresponds to the peak value of the electric field under the drain region (EUD), depends on the HBM robustness. By using the Electrical field under Drain (EUD) region to optimize die characteristics by adjusting various parameters, the team improved the HBM robustness while achieving a voltage of 25 to 96V. This also reduced the die size by half for a 80V fully isolated Nch-LDMOS products with +/-4kV ESD protection.
Toshiba has produced prototypes of devices using its automotive 130nm BiCD-0.13G3 process and plans to start mass production in 2018. The designs can also be applied in the CD-0.13G3 process for motor control drivers and CD-0.13G1/G2 for power management ICs.
The technology was described at the International Symposium on Power Semiconductor Devices and ICs 2017 in Japan this week.
To find out more visit www.toshiba.co.jp
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