AVS 51st International Symposium
    Electronic Materials and Processing Monday Sessions
       Session EM-MoP

Paper EM-MoP8
Influence of Molybdenum on the Whisker Formation of Al Film

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: C.F. Lo, Praxair Electronics
Authors: C.F. Lo, Praxair Electronics
D. Draper, Praxair Electronics
P. McDonald, Praxair Electronics
P. Gilman, Praxair Electronics
Correspondent: Click to Email
This study was to understand if addition of Mo can minimize whisker formation of Al film. Four Al-Mo alloys with 5at%, 10at%, 15at% and 40at% Mo, respectively, plus one pure Al were deposited to glass substrates by physical vapor deposition. The as-deposited and 350C/1hour annealed films were characterized by the SEM-EDS and XRD. Many hillocks were observed on the as-deposited and annealed Al films, but no whisker was found. The as-deposited Al-5at% Mo film has a similar microstructure as that of the Al films. An enormous amount of whiskers with various shapes were formed after annealed. For the Al-10at%Mo and the other higher Mo content films, the hillocks were significantly reduced and no whisker was found. The XRD measurements showed that the Al and Al-10at% Mo films were (111) grain orientation dominant. The Al-5at% Mo, however, has the similar amount of (111) and (200) orientations. No grain orientation could be identified for the Al-15at%Mo and Al-40at% Mo films. Focusing on the whisker formation of the Al-5at% Mo film, a group of films annealed at 350C for 1 to 20 minutes were prepared. Increasing the holding time reduced the (111) oriented grains, while the (200) ones were not significantly changed. In addition, a new phase was formed after annealing. The results show that with at least 10at% addition of Mo, the hillock can be minimized and no whiskers will be generated. Addition of 5at% Mo, however, will generate whiskers by annealing at 350C. Formation of the whiskers on the annealed Al-5at% Mo was ascribed to the co-existence between the (111) and (200) oriented grains, which caused a higher internal stress as result of mismatch of the grain orientations. During annealing, to reduce the internal stress, the whiskers were generated.