具有HfN/HfO_2栅结构的p型MOSFET中的负偏置-温度不稳定性研究

Negative bias temperature instability of HfN/HfO_2 gated p-MOSFETs

研究了HfN/HfO_2高K栅结构p型金属-氧化物-半导体(MOS)晶体管(MOSFET)中,负偏置-温度应力引起的阈值电压不稳定性(NBTI)特征.HfN/HfO_2高K栅结构的等效氧化层厚度(EOT)为1·3nm,内含原生缺陷密度较低.研究表明,由于所制备的HfN/HfO_2高K栅结构具有低的原生缺陷密度,因此在p-MOSFET器件中观察到的NBTI属HfN/HfO_2高K栅结构的本征特征,而非工艺缺陷引起的;进一步研究表明,该HfN/HfO2高K栅结构中观察到的NBTI与传统的SiO2基栅介质p-MOSFET器件中观察到的NBTI具有类似的特征,可以被所谓的反应-扩散(R-D)模型表征:HfN/HfO_2栅结构p-MOSFET器件的NBTI效应的起源可以归为衬底注入空穴诱导的界面反应机理,即在负偏置和温度应力作用下,从Si衬底注入的空穴诱导了Si衬底界面Si-H键断裂这一化学反应的发生,并由此产生了Si+陷阱在Si衬底界面的积累和H原子在介质层内部的扩散,这种Si+陷阱的界面积累和H原子的扩散导致了器件NBTI效应的发生.

The negative-bias temperature instability （NBTI） characteristics of HfN/HfO2 gated p-MOSFET with equivalent oxide thickness （EOT） of 1.3nm and low pre-existing traps are studied. Due to the low pre-existing trap density of HfN/HfO2 gate stack, the observed NBTI characteristics are intrinsic, rather induced by the fabricating process. The observed characteristics can be compared with those reported in SiO2 based gate stack and can be explained with the generalized reaction-diffusion （R-D） model： under negative bias and temperature stressing, holes injected from the Si substrate could cause the Si-H bond breaking at the Si substrate interface. The H atoms diffuse away into the bulk layer and the Si^ ＋ species are left at the interface. The diffusing H atoms and the left Si^＋ species cause the NBTI characteristics.