Frequency Than The Dual-frequency Capacitively Coupled Plasma Sio <sub> 2 </ Sub> Etching

The rapid development of semiconductor industry has enhanced the low-temperature plasma processing technology to be continuously improved. To satisfy the ultra-fine line width etching of dielectrics with high precision a dual-frequency excited capacitive coupled plasma source had been proposed. On the one hand, high frequency power can generate a high-density plasma, on the other hand, low frequency power applied to the electrode can control the ion bombardment energy onto the electrode. With appropriate dual-frequency configuration, decoupling the ion flux and ion energy can be realized. In other words, the ion flux and ion energy in the dual-frequency capacitive coupled plasma can be controlled independently. This feature of dual-frequency capacitive coupled plasma will expand the plasma etching process window to achieve an etching ability with high-fidelity.In this study, with two kinds of different frequency configuration (60MHz/2MHz and 40.68 MHz/13.56MHz) to generate capacitive coupled plasma, etching experiments of SiO₂ dielectric are investigated by changing the source gas flow ratio (R = [CHF₃] / ([CHF₃] + [Ar])), radio frequency source power, self-bias voltage and other conditions of the SiO₂ dielectric etching. The experimental results shows that, compared to the low ratio frequency configuration, the high ratio frequency configuration is more beneficial in decoupling the two frequencies, which have more independent control of ion flux and ion bombardment energy; Additionally, due to a decrease in power consumption of ion in sheath and a increase in power consumption of electron in bulk plasma, higher frequency ratio configuration is propitious to get a higher dielectric etching rate than lower frequency ratio configuration. The result of SiO₂ surface morphology shows that the frequency configuration of high frequency ratio is conducive to the decline in surface roughness. The results from X-ray photoelectron spectroscopy of SiO₂ etching surface show that the increase of negative bias can not only enhance reaction between fluorocarbon layer and SiO₂ and thus improve SiO₂ etching, but also enhance the surface reaction of fluorocarbon layer, and occurs the decrease in fluorocarbon bond content with lower bond energy.