薄硅膜SOI LDMOS器件的HCI劣变机理研究

Study on HCI degradation mechanism of thin silicon film SOI LDMOS devices

由于薄硅膜——绝缘体上硅型横向扩散金属氧化物半导体(Silicon On Insulator Laterally Diffused Metal Oxide Semiconductor,SOI LDMOS)制作在厚度仅有几十到几百纳米的硅膜上,器件在高电压、大电流的作用下,热载流子注入(Hot Carrier Injection,HCI)效应更为复杂,HCI可靠性受到极大的挑战。研究并探讨了两种结构的15 V SOI LDMOS的热载流子注入劣变机理。采用电荷泵(Charge Pumping)方法测试了界面缺陷产生的特点,当HCI效应发生在沟道区,最大沟道跨导退化明显,饱和驱动电流退化幅度较小,当HCI效应发生在多晶栅边缘,情况刚好相反。通过TCAD仿真研究了器件结构和碰撞电离率分布规律,发现了碰撞电离产生的负电荷对漂移区影响机制,揭示了HCI效应即碰撞电离率最大的位置对SOI LDMOS器件的损伤机理。为薄硅膜SOI LDMOS器件的HCI可靠性设计与优化提供了重要的经验参考。

Because Silicon On Insulator Laterally Diffused Metal Oxide Semiconductor(SOI LDMOS)is manufactured on silicon film with a thickness of only tens to hundreds of nanometers.Under the action of high voltage and high current,the effect of Hot Carrier Injection(HCI)is more complicated,and the reliability of HCI is greatly challenged.In this paper,the hot carrier injection degradation mechanism of 15 V SOI LDMOS with two structures has been studied,and the characteristics of interface defects have been tested by the Charge Pumping method.When the HCI effect occurs in the channel region,the maximum channel transconductance degradation is obvious,and the saturation driving current degradation is relatively small.When the HCI effect occurs at the edge of the polycrystalline gate,the situation is just the opposite.The device structure and the distribution law of impact ionization rate are studied by TCAD simulation,and the influence mechanism of the negative charge generated by impact ionization on the drift region is found,and the damage mechanism of the SOI LDMOS device is revealed by HCI effect,that is,the position with the highest impact ionization rate.It provides an important experience reference for HCI reliability design and optimization of thin silicon film SOI LDMOS devices.