功率VDMOS器件高温直流应力下退化及失效机理研究

Study of the Degradation and Failure Mechanism of Power VDMOS Devices Under High Temperature and Direct Current Stress

研究了垂直双扩散金属氧化物半导体(VDMOS)功率器件在高温和直流应力下的退化和失效过程及机理。测量了栅极阈值电压[U_(GS(th))]、栅极-源极漏电流(I_(GSS))、静态漏极-源极通态电阻[R_(DS(on))]、漏极-源极击穿电压(U_(DSS)),发现R_(DS(on))在应力时间672～864 h范围内开始变大直至测试结束,其他各项电学参数总体保持稳定。测量了器件结到热沉的热阻(R_(TH)), R_(TH)保持稳定。研究表明器件的栅极、漏极、器件内部结构和焊料、管壳基本不受应力影响。对烧毁的器件进行微区分析,扫描电镜图片表明损坏区域在源极上表层和源极引线位置,和电学参数、R_(TH)值的分析相一致。R_(DS(on))的增加是由包括引线在内的源极封装和源极欧姆接触电阻增大导致,超过阈值时将导致器件烧毁。研究结果有助于提高恶劣工况下的VDMOS功率器件可靠性。

The degradation and failure mechanism of power vertical double diffusion power metal-oxide-semiconductor(VDMOS)devices applied under high temperature and direct current stress were studied.The gate threshold voltage[UGS(th)],gate-source leakage current(IGSS),static drain-source on state resistance[RDS(on)],drain-source breakdown voltage(UDSS)were measured.It is found that RDS(on)begins to increase in the range of 672 to 862 hours until the test is over,the other electrical parameters approximately remain stable.The junction-sink thermal resistances(RTH)were measured,they remained stable.The results show that the stress nearly has no influence on the gate,the drain,interior of the device,the solder and the case.The analysis of micro zone is performed on the damaged device and the scanning electron microscope image shows that the damaged part is located at the area including the top surface of the source and the source lead,which is consistent with the analysis of the electrical parameters and RTH.The increase of RDS(on)is due to the resistance increase of source package including the lead and source ohmic contact,which will induce the device damage when exceeding a threshold value.The study contributes to improving the reliability of power VDMOS devices under harsh condition.