Surface modification for surface deactivation effects using CH4 plasma treatment

Abstract

Plasma treatment is a promising surface modification method and has been studied in various fields such as the semiconductor industry, nano printing, and nanocoating. Depending on the type of plasma, this method, which can cause chemical transformations on the surface, is particularly relevant for deposition techniques in the semiconductor industry. Plasma treatment is also being studied as a deactivation step that induces selective growth on the surface in area selective atomic layer deposition (ASALD). Therefore, there is a need for research on an effective deactivation method capable of delaying growth by inhibiting the adsorption of precursors in the ALD cycle. This study introduces a surface modification method that can deactivate the surface of a substrate. When plasma treatment is performed on a silicon substrate through CH4 gas, an organic layer of carbon is formed on the surface and the wettability is changed. The wettability of the surface as measured by the water contact angle (WCA) showed a change with plasma exposure time. After 5 seconds of CH4 plasma treatment time, the contact angle increased from 64 degrees to 82 degrees. This was due to the hydrophobic organic layer created on the surface after plasma treatment. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analysis after plasma exposure to the surface confirmed the formation of hydrocarbon hydrophobic groups on the surface. Like the WCA result, the largest C-H peak was confirmed at the plasma treatment time of 5 seconds. These hydrocarbons formed on the surface can lower the surface energy. The chemical bonding state of the modified surface with a 5 second plasma treatment time can provide great insight into how the surface reacts with other molecules. Therefore, in this study, it was confirmed that the hydrophobic hydrocarbon groups generated on the Si surface after 5 seconds of plasma treatment can passivate the surface to inhibit the adsorption of [bis(dimethylaminomethylsilyl) -trimethylsilyl amine] DTDN2-H2 precursor. Through the FT-IR result after precursor injection, the N-H peak due to the DTDN2-H2 was observed in the bare Si, while the decreased N-H peak was confirmed on the CH4 plasma-modified surface. The surface deactivation step using CH4 plasma can be incorporated into the ALD cycle to deactivate the surface and inhibit the adsorption of precursors. The amount of hydrocarbon produced by the CH4 plasma treatment may vary depending on the type of surface, so it can be later applied to area selective deposition studies.