Using Simulation to Investigate and Control RSCE Effects of 28 nm nMOSFETs with HK/MG stack.

• Main Authors: Jia-Siang Lan, 藍嘉祥
• Other Authors: Mu-Chun Wang
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/48n36n

碩士 === 國立臺北科技大學 === 機電整合研究所 === 103 === In the recent research, introducing the high-k/metal-gate (HK/MG) on advanced MOSFET devices replacing the conventional oxynitride (SiON)/poly-gate is a main trend. However, due to the advanced progress of process technology, the gate channel lengths of modern MOSFETs are being shrunk continually, but this progress also brings the short channel effect (SCE) and the Vt roll-off phenomenon to the MOSFETs. Using the pocket implant to avoid this effect is helpful, but, unfortunately, this implant process will generate the Vt roll-up phenomenon called the reverse short-channel effect (RSCE), which also causes another problem for circuit operation and reliability. Referring the aforementioned, the MOSFETs must be controlled for the threshold voltage and alleviate the RSCE effect in the short channel device. Therefore, the simulation software has been employed to find the optimal process to soften the RSCE consequence. In this study, the Technology Computer Aided Designer (TCAD) software is adopted to simulate the electrical characterisitcs and RSCE effect of 28 nm MOSFETs under the decoupled plasma nitridation (DPN) process with different annealing temperatures and nitrogen concentrations. One of nMOSFETs with HfOx as the high-k (HK) layer to establish the simulation model was executed completely. After the establishment of the simulation model, the availably tuned parameters include the doping dose and energy of lightly-doped drain (LDD) and pocket implant as well as the deposited thickness and work function of the metal gate. Recording all of Vt values under the different process recipes, the difference of measured electrical data will be compared to the simulation results. In simulation, we observed that the RSCE effect with the smaller work function, TiAl, is better than that with the larger, TiN. For the consideration of the deposited thickness with Ti/TiN, the smaller deposited thickness in the RSCE effect is improved more due to the little existence of the SCE effect compromising the RSCE effect. Finally, the simulation results referring the real electrical performance of 28 nm nMOSFETs to adjust the simulation parameters approach the actual extracted electrical results well.