Paper PS2-TuA4
Molecular Dynamic Simulation of Possible Damage Formation at Vertical Walls of finFET Devices during Plasma Etching Processes

Tuesday, October 30, 2012, 3:00 pm, Room 25

Development of multi-gate field effect transistors (FETs) such as fin-type FETs (finFETs), which can suppress short channel effects, have been considered as a leading approach to continue to follow Moore’s law after the current planer MOSFET technologies reach the size limitations. In finFETs, the Si vertical walls are typically designed to function as gate channels and therefore damages at the vertical walls possibly caused by ion bombardment during the gate etching processes must be minimized. During such etching processes, ions may impinge upon the vertical surfaces but their angles of incidence should be nearly grazing angles. Energetic ions at large oblique angles of incidence against the surface are often considered to be less harmful than those with normal angle of incidence if their incident energies are the same. However, a recent study [1] performed by mass- selected ion beam system has shown that H⁺ ion injection at 60 degree from the surface normal can form a deep damage later near the substrate surface. In addition, it is known that simultaneously injection of H⁺ ions and O atoms cause enhanced surface oxidation on the Si substrate [2]. In this study, we have used molecular dynamics (MD) simulations to study damages caused by ion bombardment with oblique angles of incidence. It has been found in MD simulations that light ions such as H⁺ can indeed cause a deep damaged layer near the substrate surface even at large angle of incidence whereas heavier ions such as Br⁺ ions cause less damages under the same conditions.

[1] T. Ito, K. Karahashi, K. Mizotani, M. Isobe, S.-Y. Kang, M. Honda, and S. Hamaguchi, Jpn. J. Appl. Phys. (2012) in press.

[2] T. Ito, K. Karahashi, M. Fukasawa, T. Tatsumi and S. Hamaguchi, Jpn. J. Appl. Phys. 50 (2011) 08KD02.