小尺寸功率VDMOS晶体管中准饱和效应的研究

Investigation of Quasi-saturation Effect in Small Size Power VDMOS

分析了功率VDMOS晶体管在小尺寸时准饱和效应的成因,并对其进行了理论证明和模拟验证.研究结果表明,在晶体管导通状态下,由于寄生JFET电阻Rj和MOS沟道电阻Rch的分压作用,致使在MOS沟道内载流子漂移速度由饱和变为不饱和,而在寄生JFET沟道中载流子漂移速度由不饱和变为饱和,造成器件在高栅源电压VGS时,器件漏端电流IDS大小与栅源电压VGS无关,从而形成准饱和效应.

In small size power VDMOS transistors, the cause of quasi-saturation effect has been investigated and simulated by software. Due to the resistance distribution of R _j and R _ ch in the device, carriers' drift velocity in MOS channel changes from saturation to unsaturation while the carriers' drift velocity in the autoecious JFET channel changes from unsaturation to saturation. When the device is in high V _ GS , I _ DS is independent of V _ GS , resulting in the quasi-saturation effect.