Study Of Electro-thermal Characteristic Co-optimization On Floating P-type Trench Gate LDMOS

LDMOS is widely applied in power semiconductor integrated circuits owing to its outstanding withstand voltage ability,strong driving ability,high frequency and easy integration.Breakdown voltage,specific on-resistance and gate-to-drain charge are several critical performance parameters of LDMOS.For a long time,researchers have been committed to the compromise among them.On the one hand,improve the contradictory relationship between BV and R_on,spof LDMOS,making it close to or beyond the ideal silicon limit.On the other hand,reduce the Q_gd of the device towards high-frequency applications,so as to improve the switching characteristics.Furthermore,owing to the high power density,the self-heating effect in LDMOS devices is serious,which leads to the degradation of key performance parameters and reliability problems.Based the above problems,in this paper,we propose a LDMOS device structure which can achieve the co-optimization of static and switching characteristics,and the electro-thermal characteristics of the device are co-optimized by electro-thermal coupling simulation.The main research contents are as follows:1.A Floating P-type Trench Gate LDMOS device is proposed,which has a low R_on,sp and Q_gdwhile maintaining a certain BV level.The BV,R_on,sp and Q_gd of the optimized device are 69.61 V,0.2257 m?·cm~2 and 55.30 n C/cm~2,respectively.Compared with Multi-plane Accumulation Layer LDMOS and Split Trench Gate LDMOS,the R_on,sp and Q_gd of FPTG-LDMOS are reduced by 47.21%and 37.31%,respectively,and the co-optimization of static and switching characteristics is realized.The proposed device exhibits an excellent performance.2.The optimal parameter combination is determined to realize the compromise among key performance.And the effects of key structure,doping parameters on the static and switching characteristics of FPTG-LDMOS device are explored.After optimization,the power and loss figure of merit of the device reach 21.47 MW/cm~2 and12.48 n C·m?,respectively.The performance is obviously superior than that of trench gate devices with the same withstand voltage level.Meanwhile,High-K dielectric is introduced,but the BV deteriorates due to the limited dielectric constant and critical breakdown electric field of the material.Therefore,the conventional High-K materials are not suitable for FPTG-LDMOS,which provides a guidance for future device optimization.3.The co-optimization of electrothermal characteristics of FPTG-LDMOS is realized,and the self-heating effect of bulk and silicon on insulator FPTG-LDMOS are analyzed,and their self heating mechanisms are revealed.The results show that the self heating effect in SOI is more server than bulk.Based on SOI FPTG-LDMOS structure,a scheme of reasonably opening silicon window in the buried oxide layer of the device to realize the co-optimization of the electro-thermal characteristics of the device is proposed.The results show that the BOX layer silicon window can effectively improve the thermal characteristics without affecting the electrical performance of the device.In the optimal design scheme,the thermal characteristics of the device are improved by18.5%,the purpose of co-optimization of electro-thermal characteristic is achievedIn conclusion,the proposed FPTG-LDMOS realizes the compromise between static and switching characteristics and the co-optimization scheme of electro-thermal characteristics is proposed,which reduces the overall loss of the device and improves the thermal reliability.It can be applied to the fields of medium-to-low voltage automotive electronics and communication base stations within 100 V.