基于电容结构的α-SiGe∶H膜电学退化特性

Electrical Degradation Characteristics of α-SiGe∶H Film Based on Capacitance Structure

针对航天一次可编程(OTP)存储器高可靠应用需求,基于电容结构和肖特基接触模型,分析得出α-SiGe∶H膜退化前电流传输机制较好地符合热电子发射-扩散模型,并计算得到零偏α-SiGe∶H/TiW界面肖特基势垒高度为0.41 eV。通过实验发现,在电压应力作用下,α-SiGe∶H膜漏电随时间增大并逐渐饱和,且不同应力电压下对应饱和漏电大小及饱和点时间不同。分析应力下漏电增大与非晶网络弱键断裂造成的缺陷相关,漏电机制由初始的扩展态主导转变为由缺陷密度决定的局域态主导,漏电饱和归因于α-SiGe∶H膜中缺陷密度的饱和,采用近邻跳跃电导模型可以很好地拟合实测J-V曲线,并计算得到饱和缺陷密度为5×10^19 eV^-1·cm^-3。

Aiming at the high reliability application requirement of one-time programmable(OTP)memory in the aerospace field,based on the capacitance structure and Schottky contact model,it was analyzed that the current transport mechanism ofα-SiGe∶H film before degradation was in accordance with the thermal electron emission-diffusion model.The Schottky barrier height of the zero biasα-SiGe∶H/TiW interface was calculated to be 0.41 eV.It is found that theα-SiG∶H film leakage increases with time and gradually saturates under the voltage stress in the experiment,and the corresponding saturation leakage and saturation time are different under different stress voltages.It is analyzed that the increase of leakage under stress is related to the defect caused by the broken weak bond in the amorphous network.The predominant factor of leakage mechanism changes from the initial extended state to the local state determined by the defect density.The leakage saturation is due to the saturation of the defect density in theα-SiG∶H film.The measured J-Vcurve can be well fitted by using the nearest neighbor hopping conductivity model,and the saturation defect density is calculated to be 5×10^(19)eV^-1·cm^-3.