NiSi金属栅电学特性的热稳定性研究

Thermal stability of electrical characteristics of nickel silicide metal gate

研究了NiSi金属栅的各种电学特性及其热稳定性,提出一个物理模型用于解释当形成温度大于500℃时NiSi功函数随退火温度升高而增大的现象.测量了不同退火温度形成的NiSi材料的方块电阻,当退火温度大于400℃时,方块电阻达到最小,并在400—600℃范围内稳定.比较各种温度下形成的NiSi材料X射线衍射谱的变化,说明温度在400—600℃范围内NiSi相为最主要的成分.制备了以NiSi为金属栅的金属氧化物半导体电容.通过等效氧化层电荷密度及击穿电场Ebd的分布研究,说明炉退火时间较长将导致NiSi金属栅与栅介质之间界面质量下降、击穿电场降低,这种退火方式不适合作为NiSi金属栅的形成方式.系统研究了在各种快速热退火(RTA)温度下形成的NiSi金属栅电容的电学特性,通过C-V,Ig-Vg曲线及氧化层等效电荷密度的比较,说明了当RTA温度大于500℃时栅介质质量明显退化,因此400—500℃为理想的NiSi金属栅形成温度范围.进一步提取并分析了400,450,500和600℃条件下RTA形成的NiSi金属栅功函数及等效氧化层电荷,发现在600℃条件下NiSi金属栅功函数和氧化层等效电荷都有一个显著的增大.

The electrical characteristics of NiSi metal gate and their thermal stability were studied. A physical model is proposed to explain the increase in NiSi work function when the forming temperature is higher than 500℃. By measuring the sheet resistance of NiSi film prepared at different temperatures, it is shown that NiSi has the lowest resistance when formed at 400℃, which is stable from 400 to 600℃. The X-ray diffraction measurement for the NiSi samples formed at various temperatures revealed that NiSi phase was the main component at temperatures from 400 to 600℃. The capacitors formed by furnace annealing has higher equivalent oxide charge Qox and lower breakdown electric field Ebd, which proves that furnace annealing is unsuitable for NiSi metal gate fabrication due to the long time of thermal processing （400℃ for 30 min）. The electrical characteristics of NiSi gate metal oxide semiconductor capacitors formed at various rapid thermal annealing（RTA） temperatures were studied. By comparing the C-V curves, ls-Vs curves and Qox of the capacitors, it was found that when the RTA temperature is higher than 500℃, reaction between NiSi and gate oxide will occurr, reducing the quality of the gate dielectric. In conclusion, the Suitable forming temperature of NiSi metal gate should be from 400 to 500℃. Moreover, the NiSi work function and Qox formed at 400,450 and 500℃ respectively were also determined.