Fabrication of Au structure using direct electroplating on Si structure

Lithography is generally used when fabricating microstructures. If the substrate is conducting, it is possible to form high aspect ratio metallic microstructures by electroplating. However, it is difficult to fabricate high aspect ratio microstructures using just resist as the masking material because the high aspect ratio required is difficult to achieve with resist. On the other hand, of high aspect ratio microstructures can be fabricated using silicon dry etching technology. Then again, good quality metallic structures can only be obtained by plating up from the bottoms of the etched grooves. Because it is difficult to form a seed layer just on the bottoms of the grooves, it is difficult to fabricate metallic microstructures in high aspect ratio grooves etched using silicon dry etching technology. To solve this problem, we developed a new fabrication method in which metallic microstructures are fabricated by electroplating directly into grooves etched in the Si after the sidewalls of the grooves have been coated with an insulating film. Au electroforming was accomplished from the bottoms of grooves etched into silicon. We were able to fill the etched grooves with Au over an area of 60mm squares. The depth of the grooves, and hence the thickness of the Au was 4μm, and the pitch was 5.3μm. Moreover, fabricating Au microstructures in deeper higher aspect ratio grooves was also attempted. As a result, 20 μm deep grooves were filled to a depth of 18μm with Au. It is expected that this technology can be used in the production of a wide variety of devices.