Application of novel ultrasonic cleaning equipment using waveguide mode for post-chemical-mechanical-planarization cleaning

In this paper, we propose the application of novel ultrasonic cleaning equipment using a waveguide mode, which we called the Megatube, to post chemical mechanical planarization (CMP) cleaning. Waveguides can be created in a curved shape, and ultrasonic waves of 1 MHz, within the megasonic frequency range, can propagate along such waveguides. It is possible to supply ultrasonic waves at a distance from the equipment, which has the advantage of enabling ultrasonic emission in a narrow space. For single-wafer processing, this technique has the advantage of removing particles, known as slurry residues, from both the front and back sides of the wafer by exposure to ultrasonic waves of megasonic frequency. In the Megatube, cavitation is generated by controlling the input power and the dissolved gas concentration. Particle removal efficiency (PRE) using the Megatube was evaluated for various input powers, waveguide tube lengths, and concentrations of dissolved gas in a cleaning solution.