R. Ramesh , H. Younan, Chartered Semiconductor Mfg Ltd, Singapore, Singapore

Summary: Al bondpad is a very important constituent of an IC microchip, even in advanced technologies such as 65nm, 45nm, 40nm & 32nm/28nm. As the bondpads are used to communicate, electrically, with other parts of circuitry, its surface qualification becomes very important in order to reduce/eliminate non-stick on pad (NSOP) problem during assembly process. It is well known fact that particles, Si-dust contaminations, corrosion-induced defects and underetch residue may contribute to NSOP. In authors’ previous studies, the pinholes/defects/underetch residue due to galvanic corrosion (Hua et al, IFTFA1998, 2000 & 2006), fluorine-induced corrosion (Hua et al, IFTFA2002, 2003 & 2008), underetch of wafer fab process (Hua et al, IFTFA1999) and Si dust of wafer die sawing (Hua et al, IFTFA2006) have been studied & discussed. In this paper, a qualification method of microchip Al bondpads will be introduced. According to this method, a good quality Al bondpad should be defect free, with low contamination level (such as fluorine and carbon contamination should be within a control limit) and with a passivation layer on bondpad surface so as to prevent bondpad corrosion. The OSAT (Optical, SEM, Auger and TEM) failure analysis method is recommended for the qualification of Al bondpads. A good quality Al bondpad will help to eliminate NSOP in wafer fabrication.