Improved electrical characteristic of negative bias temperature instability

• Main Author: Hu, Youzhou.
• Other Authors: Ang Diing Shenp
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/51133
• Institution: Nanyang Technological University

Negative Bias Temperature Instability (NBTI) is a critical reliability issue of metal-oxide-semiconductor field effect transistors (MOSFETs) due to imperfections located at the oxide-semiconductor interface and in the gate dielectric. As the major characteristic parameter of NBTI, the threshold voltage shift is very important to be monitored under the NBTI stress. Therefore, many methods including conventional methods and some fast characterization techniques have been developed to extract the threshold voltage shift in the subthreshold and strong inversion region. However, there are still some unclear issues of NBTI, such as the different threshold voltage shift extracted from different techniques, the recovery of the slow measurement method, and the mobility degradation during NBTI stress, etc. Therefore, the goal of this project is to investigate these significant problems.Firstly, the comparison of different fast characteristic techniques is studied with an Agilent B1500 setup.Secondly, an ultra-fast switching method with 40ns stress interruption interval is presented with the application of Keithley pulsed I-V setup; the necessary drain current correction is applied to the ultra-fast switching method in order to obtain the accurate drain current.In order to avoid the overestimation of the conventional 3-parameter model, a new threshold voltage extraction method in the strong inversion region named the Ratio Method is presented; it can also separate the low field mobility, scattering parameter and the source/drain series resistance effect.Thirdly, the characteristic of NBTI in the strong inversion region is studied. With the help of the Ratio Method, the low field mobility of the channel is investigated; the obvious degradation of low field mobility is observed. The overestimation of the 3-parameter model is investigated using the Ratio Method. Finally, the characteristics of the subthreshold region are investigated.With the help of this UFS method, the subthreshold characteristics of short channel p-MOSFETs have been studied. The degradation of subthreshold swing is observed under NBTI stress.