Development of a Single-beam Megasonic System for Nano-particle Cleaning

A single-beam megasonic system for nano-particle cleaning which does not cause nano-scale pattern damage was designed. Considering ultrasonic wave propagation, a length of quartz waveguide was decided at a uniform acoustic wave region. The anti-resonance frequency of the piezoelectric actuator was measured to be 987 kHz, which agreed well with the fabricated quartz waveguide operating frequency of 983 kHz. The acoustic pressure of the single-beam megasonic system was measured, and the averaged value increased by 89% compared with a commercially available product (named an A-type). To compare uniformity, standard deviations of acoustic pressure values were calculated, and they were lower than A-type results by 20%. In addition, particle removal efficiency (PRE) tests were performed, and 91% of particles were removed after megasonic cleaning. These results explain our system's performance improvement in PRE and reduction in nano-pattern damage.