| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS2-TuM |
| Session: | Advanced FEOL/Gate Etching |
| Presenter: | Y. Muraki, Osaka University, Japan |
| Authors: | Y. Muraki, Osaka University, Japan H. Li, Osaka University, Japan T. Ito, Osaka University, Japan K. Karahashi, Osaka University, Japan M. Matsukuma, Tokyo Electron Ltd., Japan S. Hamaguchi, Osaka University, Japan |
| Correspondent: | Click to Email |
Reactive ion etching (RIE) by halogen-based plasmas such HBr plasmas are widely used for Si etching in semiconductor manufacturing processes. It has been know that, for a Si surface, Br ions have high etching yields, high selectivity over SiO2 and SiN, and high etching anisotropy. However, in recent years, as non-classical CMOS structures such as vertical multi gates have been introduced for near-future devices, there has been a concern on possible damages caused by highly energetic hydrogen ions (H+) that hit a Si surface even at grazing angles. For vertical multi gates, the Si surfaces subject to direct ion bombardment function as gate channels, ion bombardment damage to the surface must be minimized. In this study, we have evaluated sputtering yields of Si by Br+, H+ and SiBr+, as functions of incident energy in the range from 300 eV to 1000eV as well as functions of the incident angle. We have also examined Si substrate damages caused by ion bombardment by transmission electron microscopy (TEM) and High-resolution Rutherford Backscattering Spectrometry (HRBS). It has been found that there is strong angle dependence of the Si etching yield by Br+ ion irradiation, which indicates that Br+ ion etching has also an aspect of physical sputtering despite its high chemical reactivity with Si. Although, in actual HBr plasma processing, simultaneous surface passivation by Br radicals makes its Si etching more chemical, the nature of physical sputtering by energetic Br+ ion bombardment ensures anisotropic etching. The depth of damages in a Si substrate caused by Br+ ion bombardment, on the other hand, decreases with its angle of incidence as Br+ ions cannot penetrate deeply into the substrate at higher incident angles. However, it has been also found that energetic H+ ions can be damaging to the Si surface even at large incident angles since, due to their small mass, incident H+ ions are scattered nearly isotropically when they hit the substrate surface. In addition, due to their small atomic size, H+ ions penetrate far more deeply than Br + ions do. Furthermore it has been found that SiBrx+ ions can be deposited at low energy. Since, at relatively high-pressure, SiBrx+ ions can be rather abundant in HBr plasmas for Si etching. Therefore care must be taken in developing HBr etching processes for vertical multi gates to avoid surface damages by H+ ions and to control the profiles despite incident and/or re-sputtered species with higher sticking probabilities.