Effects of fabrication method on defects induced by nitrogen diffusion to the hafnium oxide layer in metal-oxide-semiconductor field effect transistors

Publication date: Available online 3 November 2016
Source:Thin Solid Films
Author(s): Ying-Hsin Lu, Ting-Chang Chang, Szu-Han Ho, Ching-En Chen, Jyun-Yu Tsai, Kuan-Ju Liu, Xi-Wen Liu, Chien-yu Lin, Tseung-Yuen Tseng, Osbert Cheng, Cheng-Tung Huang, Wei-Ting Yen
This study investigates how different metal gate fabrication methods induce variations in the defects which result from nitrogen diffusing into the hafnium oxide layer in metal-oxide-semiconductor field effect transistors (MOSFETs). By using the different fabrication methods of pre-TaN, post-TaN and post-TiN annealing, the work-function difference between the gate material and the semiconductor can be adjusted, leading to apparent differences in threshold voltage (Vth). In addition, the results of slow and fast I-V NBTI measurements show that the amount of the bulk trapping in the post-TiN device is the highest, followed by the post-TaN device and then the pre-TaN device. In addition, a nitrogen interstitial defect phenomenon, resulting in a temporary shift of threshold voltage (Vth) which is highest in the post-TiN the lowest in the pre-TaN device, as determined by double sweep fast I-V measurements.