Fabricating HARMS by using megasonic assisted electroforming

Electroforming is a main fabrication method to produce metal microstructures for microelectromechanical systems. Since the mass transport is limited in high aspect ratio microstructures (HARMS), problems such as uneven filling and void formation are often involved in the electroplating of deep molds. In this work, megasonic agitation is employed to improve the electroplating of HARMS, which causes little damage to the resist structure and is thereby advantageous over ultrasonic agitation. Cantilever beams and gaps with a linewidth of 10 μm and an aspect ratio of 25 have been obtained. The main effects of megasonic agitation are analyzed. The results indicate that resonant bubbles in the electrolyte are probably responsible for the mass transport enhancement during the electroforming process.