Research On Back Gate Modulation Model And Characteristics For Thin Layer SOI High Voltage LDMOS

SOI(Silicon On Insulator,silicon on insulator)high-voltage LDMOS(Lateral Double-diffused Metal Oxide Semicondutor)is widely applied in smart power integrated circuits such as automotive electronics,medical electronics,smart appliance and aerospace because of low power dissipation,high frequency and high integration.Compared with thick layer SOI LDMOS,thin layer SOI LDMOS provides good technology compatibility and less parasitic effects,which results in the good prospects in power integrated circuits,expecially in power switching and driver.However,due to the presence of back gate(BG)effect,the performance and reliability of thin layer SOI LDMOS,especially of p-channel LDMOS,is influenced.So far,the study of BG effect focuses mainly on the impact on breakdown voltage(BV),and less care are devoted to the impact of BG effect on specific on-resistance(Ron,sp)and negative bias temperature instability(NBTI)which is one of the most important reiliability issue for p-channel MOS device.Buried oxide layer of SOI is long-term impacted by BG bias,which could lead to NBTI effect inluencing the performance.However,the study of NBTI effect focuse mainly on the gate oxide layer,less on buried oxide layer.Based on electric field-charge modulation theory,centering on the BG effect,the Ron,sp,BV and trap charge induced degradation effect are investigated for the thin layer SOI high voltage field p-channel LDMOS.The BG-electric field modulation breakdown voltage model is proposed,revealing the BG effect mechanism on the relationship between BV and Ron,sp.The bulk electric field is modulated by BG bias,and then bulk charge distribution is changed which forms the dual conduction mode improving significantly the relationship between BV and Ron,sp.Conductance modulation model is proposed,revealing degradation mechanisms for the BG NBTI and hot carrier effects.Due to trap charges induced by BG NBTI and hot carrier effects,bulk charges distribution is varied which leads to the degradation.Main innovation points are list as below: 1.BG-electric field modulation breakdown voltage modelBased on electric field-charge modulation theory,the BG the BG-electric field modulation breakdown voltage model is proposed and the effect mechanism on the relationship between BV and Ron,sp is revealed.Bulk electric field is modulated by BG bias,resulting in the linear relation between BV and BG voltage: BVs = 0.98 × VBG – 198.4.In addition,the modulated bulk electric field induces the charge distribution variation,which gives rise to the dual conduction mode.Therefore,the Ron,sp for thin layer SOI high voltage field p-channel LDMOS is dependent on the result of the drift conduction layer and accumulation conduction layer in parallel: Ron,sp = 1/(1.45×10-13 ts ND – 7.07 ×10-4 VBG),which improving significantly the relationship between BV and Ron,sp.2.BG punch-through criteria and breakdown design criteria.BG punch-through criteria is proposed to reveal the BG punch-through mechanism,which is used for all SOI p-channel LDMOS device.The breakdown design criteria for thin layer SOI high voltage field p-channel LDMOS is proposed: VHV ?|BVs(VBG = VHV)|,|BVb| and |BVp|,which taking both the drain voltage and BG voltage into account.Experiment results show the BV reaches-366 V and Ron,sp is only 6.6 ??mm2.Based on the study result,the thin layer SOI high-lown voltage compatible integrated technology is developed with application in defense equipment which receives the good society and economy benefit.3.Trapped charge conduction modulation model for thin layer SOI high voltage field p-channel LDMOSTrapped charge conduction modulation model is proposed for thin layer SOI high voltage field p-channel LDMOS with revealing the degradation mechanisms for the BG NBTI and hot carrier effects.Due to trap charges induced by BG NBTI and hot carrier effects,bulk charges distribution is varied which leads to the linear current(Idlin)degradation.BG NBTI induced positive charges in buried oxide layer reduce the charge density in accumulation layer,the electric field peak and energy band at the breakdown point,which leads to Idlin decreasing,BV and static current increasing.Hot carrier effect induced Idlin degradation is dependent on the net effect of two different hot carrier meachnisms.Hot hole injection in channel causes the positive trap charges,which leads to threshold voltage increasing and Idlin decreasing.Hot electron injection in the drift region at the end of gate field plate causes negative trap charges,which leads to Idlin increasing.