A study on Al bondpad grain boundaries and galvanic corrosion in wafer fabrication

Galvanic corrosion on microchip Al bondpads cause discoloration and nonstick bondpads at assembly processes. Thus it is very important to eliminate galvanic corrosion in wafer fab and assembly houses. In this paper, Al bondpad grain boundaries and galvanic corrosion is discussed. It was found that galvanic corrosion mostly occurred at bondpad grain boundary areas. TEM results confirmed that Al oxide was not uniform at grain boundaries on Al bondpads. Therefore, we think that it can help to prevent/eliminate galvanic corrosion to grow up an Al oxide or improve uniformity of Al oxide on bondpads.