Molecular dynamic simulation of damage formation at Si vertical walls by grazing incidence of energetic ions in gate etching processes

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2015-03, Vol.33 (2)
• Main Authors: Mizotani, Kohei, Isobe, Michiro, Hamaguchi, Satoshi
• Format: Article
• Language: English
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.4907724

During gate etching processes of multigate fin-type field effect transistors (finFETs), energetic ions may hit the vertical walls at grazing angles and form damaged layers there. Such damages, if formed, can affect the device performance since part of the Si vertical walls of a finFET structure is used as a conductive channel. In this article, possible damage formation mechanisms at a Si vertical wall by energetic incidence of hydrogen ions (H+) and other heavier ions are discussed based on molecular dynamics simulation. In typical plasma processing conditions, incident ions are highly directional toward the wafer surface and therefore ions that hit such a vertical wall do so only at nearly grazing angles. It has been found in this study that the penetration depth of H+ into a Si substrate is weakly dependent on the incident angle and therefore ions at grazing incidence can form deep damage. The results indicate that, in gate etching processes with HBr plasmas or other plasmas with hydrogen, control of energetic hydrogen ion bombardment is critical in minimizing possible surface damage at Si vertical walls.