Basis knowledge about Megasonics (1/3)
The applications of acoustics in the Semiconductor industry
The main application of acoustics in the semiconductor industry is the wafer cleaning by generation of ultrasonic/megasonic waves in a process tank.
However, these megasonic waves can have other goals : the new Liquid Level Sensor from TechSonic can be mentionned, as well as the Frequency and Intensity Detector : two process tools based on megasonic waves.
What is Megasonic cleaning ?
Megasonics is a highly advanced cleaning technology for very small particle sensitive (sub-0.1µm) substrates (e.g. silicon in the semiconductor industry, but also flat panel displays, MEMS, MOEMS, etc...).
The megasonic waves (which are ultrasonic waves at higher frequencies, typically more than 700kHz - see next page) are generated by exciting a piezolectric crystal. These crystals have the interesting ability to vibrate when they are subjected to an alternative electrical field. Thus, by exciting a piezoelectric ceramic at the right frequency (its resonance frequency) and after having optimized the geometry and the physical parameters of the ceramic, a large part of the electrical energy is converted into acoustical energy (megasonic waves) which then propagates through the liquid contained in a process tank.
Sketch showing megasonic tank, transducer and recirculation flow