Effect of plasma treatment on the radiation hardness of the HfO2/Si interfacial layer

• Main Authors: Liao, Syue-Jyun, 廖雪君
• Other Authors: Tsui, Bing-Yue
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/07356723598733177493

碩士 === 國立交通大學 === 工學院加速器光源科技與應用碩士學位學程 === 103 === Extreme ultraviolet lithography (EUVL) is the most likely selection as the next generation lithography technology in the future. The radiation damage effect during exposing process should be considered because the energy of EUV is higher than chemical bonding energy of most dielectrics. The effects of oxide thickness, interfacial layer thickness, gate oxide material, and annealing temperature on the radition hardness of high-k/metal gate MIS capacitors have been studied previously. In this thesis, the radiation hardness of the HfO2/Si structure with plasma-treated interfacial layer is investigated. Moreover, we prepare the state-of-the-art n-channel Metal-Oxide-Semiconductor-Field-Effect-Transistor (nMOSFET) to study the effect of post-radiation annealing. In addition, we use positive bias temperature instability (PBTI) test to evaluate the radiation effect on the reliability property of nMOSFET. Previous study reported that ionizing radiation would induce positive oxide charge, interface traps, and border traps in the gate oxide of MIS capacitor. These defects cause capacitance-voltage (C-V) curve shift, C-V curve distortion, and increment of hysteresis. After EUV irradiation, it is observed that N2 plasma treatment increases the flatband voltage slightly. Furthermore, the increment of hysteresis is similar to that of the control sample and the interface traps increase is less than other samples. The experiment results imply that the N2 plasma treatment would improve the interface property by nitrogen incorporation. Besides, it is well suited for industrial processes. On the other side, the electrical characteristics of the NH3 plasma treated sample degrade after ionizing irradiation due to hydrogen incorporation. Evident shift and distortion of the C-V curve is observed. These results indicate that the NH3 plasma treatment is not suitable to be used in industrial processes. As the radiation source changes to 10 keV X-ray, the effect of radiation damage on the C-V curves is unobvious because the percentage of photons which are absorbed by HfO2 layer for EUV is 110 times larger than that for the 10 keV X-ray. In conclusion, N2 plasma treatment is the best choice. The worst case is the NH3 plasma treatment. As the thickness of HfO2 decreases to 5 nm, the degradation of flatband voltage and hysteresis are reduced apparently. Similarly, the N2 plasma sample still has the least flatband voltage shift and interface state generation. The worst case is NH3 plasma sample, too. Finally, we discuss the effect of annealing on radiation hardness. The state-of-the-art nMOSFET is irradiated by different radiation source. Next, it is annealed at 400 ℃. After annealing, it is exposed again to the same dose irradiation. Experimental results indicate that high temperature annealing could recover the radiation damages. Moreover, the annealing wouldn’t change the device radiation hardness. Afterward we evaluate the PBTI at weak electric field. We observe that no matter what radiation source is used, the distribution of threshold voltage degradation is nearly the same both at room temperature and 150 ℃. It indicates that the reliability property of the state-of-the-art nMOSFET wouldn’t be affect by ionizing radiation.