High Reliability Automotive-Grade 100 V LDMOS Optimization And Model Extraction

BCD process is a characteristic technology for monolithic integration of bipolar transistors,CMOS and DMOS,which has a wide chip demand and important industrial value in automotive electronics,industrial control,etc.The BCD process platform has a rich variety of device types,including low-voltage/high-voltage MOSFETs,vertical NPN transistors,Schottky diodes,JFETs,and LDMOS devices with different operating voltage,etc.In recent years,emerging applications in automotive electronics and communication electronics are on the rise,and LDMOS devices with operating voltages of 70～100 V have become a hot spot for research and development.In this paper,we have conducted research on automotive-grade 100 V LDMOS.Based on the 0.18μm BCD manufacturing process platform,we have systematically carried out the design,simulation optimization and flow testing of 100 V LDMOS,focusing on the problems of output characteristic curve upward,breakdown reliability and E-SOA reliability of LDMOS devices.The main research contents and results are as follows.For the 100 V LDMOS device,the off-state breakdown voltage（OFFBV）is greater than 110 V and the saturation current（Idsat）is 170μA/μm,but the output characteristic curve is upward.This paper proposes a widened deep N-well（DNW）design and a new LDMOS structure with stepped doping drift region composed of deep N-well and N-well（N-Well）based on the manufacturable process.The proposed solution aims to reduce the impact ionization peak.After proving the effectiveness by device simulation,the flow and test analysis were performed.The results show that the optimized LDMOS has an greater output characteristic curve,the curve shape meets the standard,and the peak bulk current(I_bulk)is reduced by 75%,the OFFBV reaches110 V,and the Idsat reaches 180μA/μm.For the reliability problem of burn-in in 60 s continuous withstanding voltage test that occurs in 100 V LDMOS,this thesis proposes to optimize the withstanding voltage reliability by increasing the doping concentration in the P-Type region,and the simulation results prove that increasing the P-Type injection dose has an optimized effect on the impact ionization rate,and the experiments results show that the P-Type injection dose in the device increases by 10%.The test data shows that the time to maintain the non-failure state of LDMOS in the continuous withstanding voltage test is extended from less than 60 s to 4.4 h,and the breakdown reliability is significantly improved.To improve the E-SOA reliability of 100 V LDMOS with open-state breakdown voltage（ONBV）not reaching 105 V,this thesis proposes an optimization scheme to improve the contact arrangement.For LDMOS without substrate bias application,a source-bulk connected layout design is used to increase the ONBV value from 103 V to 108 V,which effectively extends the E-SOA region,while layout area of 100 V LDMOS single tube is reduced by 3.9%.The optimized 100 V LDMOS device based on 0.18μm BCD process in this thesis achieves the DC characteristics and successfully passes various reliability tests such as HCI and GOI of the automotive-grade standard.The paper has completed the modeling and parameterization based on the BSIM4 model for its DC characteristics measured data,and the average error is within 3%,which meets the industry standard.This work enriches the device library of the automotive-grade manufacturing process platform and contributes to the expansion of the application of BCD process platform.