Impact of Ar/CF₄ Mixed Gas Flow Rate on Silicon Etching Using Surface Discharge Plasma

Abstract

This study examines the effects of varying argon (Ar) and carbon tetrafluoride (CF4) gas flow rates on the etching of monocrystalline silicon substrates using surface discharge plasma. While previous research has primarily focused on the fundamental characteristics and applications of surface discharge plasma in silicon etching, the influence of the gas flow rate on etching efficacy remains insufficiently explored. The aim of this study is to elucidate the relationship between mixed gas flow rates and the rate and quality of silicon etching, both of which are critical for optimizing manufacturing processes in the semiconductor industry. Utilizing a setup equipped with a USB4000 spectrometer for emission spectroscopy, we varied the Ar/CF4 flow rates from 0 to 6000 sccm while maintaining a fixed discharge-sustaining voltage of 9.4 kV. We observed and analyzed the discharge power, plasma emission intensities, and resulting etch profiles of the silicon substrates. Particularly, we analyzed the emission spectra for peaks corresponding to active species such as F, F2, and CFn, indicative of the plasma’s etching capabilities. The findings revealed that higher flow rates significantly enhanced the generation of key active species, leading to increased etching rates in both depth and width directions of the silicon substrates. Importantly, an increase in flow rate also facilitated the diffusion of these species across a broader area, thereby advancing the etching process and inhibiting the deposition of etching byproducts. These results underscore the importance of optimizing gas flow rates to enhance etching efficiency and quality. In conclusion, this study confirms that adjusting the flow rates of Ar and CF4 in surface discharge plasma etching can significantly influence the effectiveness of the silicon etching process. This outcome will contribute to the realization and development of semiconductor etching technology, such as solar cell manufacturing, as well as the further advancement of atmospheric pressure non-equilibrium plasma surface treatment technology.

Keywords

• surface discharge plasma
• etching
• Ar/CF₄ mixed gas
• gas flow rate
• silicon