The Random Dopants and Random Traps Induced Threshold Voltage Variations in Strained CMOS Devices
| Autor: | Cheng, Cheng-Ying, 程政穎 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 For the CMOS device technology with gate length 90 nm and beyond, strained technique has been a successful technology to extend the Moore’s law with further device scaling. Recent studies have revealed that the most mature CMOS technology is by the use of different strain techniques for n-MOSFET and p-MOSFET respectively. The use of SiC in the source and drain structure shows high driving current ability for n-MOSFET device. For p-MOSFET device, uniaxial structure with SiGe on source and drain with EDB (embedded diffusion barrier) seems to be promising in terms of its performance and reliability. However, as CMOS devices are scaled to the nanoscale dimension, reducing Vth variation becomes a significant issue for advanced CMOS technology. Random dopant fluctuation (RDF) is the major source of Vth variation in scaled bulk CMOS. Furthermore, stress-induced random traps fluctuation (RTF) is also considered to be another source of the enhanced Vth variation after the hot carrier stress. In this thesis, the variability of strained devices has been reported. The random dopant fluctuation induced Vth variation can be normalized by Takeuchi plot. First, the reasons for Vth variation improvement of strained devices are analyzed. The factors affecting the Vth variation which include temperature, drain bias, and substrate bias are examined. Experimental results show better variability of strained devices. Secondly, the basis of the enhanced Vth variation caused by stress-induced random traps can still follow the Takeuchi plot. The results show that the aggravated BVT is proportional to the number of interface traps. However, for strained n-MOSFETs, due to the closer distance between inversion layer electrons and interface traps, Coulomb scattering limited by interface traps becomes strongly enhanced which results in a faster aggravation of Vth variation. For strained p-MOSFETs, the aggravated Vth variation is unrelated to the strain effect. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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