Low Frequency Ultrasonic Jet for Enhanced Plating and Etching
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
High frequency ultrasonic waves can be used to enhance the morphology of electroplated deposits of gold and copper. These waves can be produced by a piezoelectric transducer at 7.5 MHz which is directed into a small jet stream of the electrolyte. However, cavitation is frequency dependent and the energy for cavitation to occur rises steeply above about 100 KHz. Also, for lower frequencies, the limiting current density is higher. Thus, while there is some advantage to the acoustic jet, the present article provides a scheme that allows a much lower frequency to be directed into the jet to achieve higher plating and etching rates afforded by the use of frequencies for which piezoelectric methods become very difficult, if not impossible.