The Impact of the Shallow Trench Isolation on the Reliability of Trigate MOSFET

• Main Authors: Wu, Chia-Wei, 吳嘉偉
• Other Authors: Chung, Shao-Shiun
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/86954388498297361375

碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 103 === For the continuing scaled down of the device’s size, many problems will be encountered such as short channel effect, random dopant fluctuation, and leakage currents. Several of these problems have been handled well in advanced CMOS technology. Among these, the trigate structure has been considered to be the candidate for the future generations. Trigate MOSFET has better gate controllability to solve the short channel effect. It also has immunity from the random dopant fluctuation because of the lightly doped channel. However, trigate devices also suffer from another problems such as side wall surface roughness, metal work function variation, and self-heating effect etc. The trigate device needs to be thoroughly studied for the future design and applications. Since the fin width is getting thinner, the STI (shallow trench isolation) are closer to the channel region, and it might have some impacts on that. In this thesis, we propose a new method to characterize the STI traps under the fin channel. Under the long term NBTI stress, the standard deviation of threshold voltage will change and by using the trigate depletion model we proposed, we can easily find the distribution of these traps under the channel region. The second part, we apply the technique to examine the radiation induced random STI traps. It is known that the X-ray will have an influence on STI traps. As the size of MOSFET shrinks down, the gate oxide is becoming so thin. However the STI oxide cannot become as thin as the gate oxide, so there are still some problems when exposing under the radiations. In the previous studies that were mainly focusing on the nuclear models or the effects of different kinds of radiations. We first combined the reliability test with the X-ray. After being exposed to the radiations, the trigate devices were then taken to the NBTI testing. The pre X-ray irradiated procedure affects the reliability a lot due to the massively increased STI traps. The on current of the device will be degraded and threshold voltage will increase due to the increased STI traps near the channel region. This result is helpful to the design of the future devices especially in the space technology.