Dual-Frequency Megasonic Waveguide for Nano-Pattern Cleaning

In this paper, a dual-frequency megasonic waveguide that is operated simultaneously by 1 and 3 MHz operating frequency, was designed and fabricated. Finite element analysis using ANSYS software was performed to design the waveguide. The predicted anti-resonance frequency (the maximum peak value of a impedance curve) for a 1 MHz piezoelectric actuator was 1000 kHz, which was in good agreement with the experimental result of 995 kHz with 0.5% error. In addition, the predicted anti-resonance frequency for a 3 MHz megasonic waveguide was 2998 kHz, which coincided with the experimental value. After manufacturing the system, acoustic pressures were measured and average acoustic pressures were calculated. As a result, average values for 1 and 3 MHz operating frequency, increased by 59.0% and 71.5%, respectively. Finally, a pattern damage test was performed with 45 nm poly-Si patterns under 4.5 W power supply for 1 MHz and 7.5 W for 3 MHz, respectively. Consequently, no pattern damage was observed. Considering these results, it is thought that the developed dual-frequency megasonic waveguide will be applicable in nano-pattern cleaning with improved efficiency.