Melt and Flow Behavior of Al into Micron Size Features Using Incoherent Radiation

Melting of Al was performed in a vacuum chamber with base pressure of ~1x10 sup (-8) torr, using a bank of ten 1.2 kW W lamps. Short heating cycles, with 3-5 sec duration from room to maximum temperature, were used. In general, heating was done from the wafer back (Si) side. Heating from the Al side required higher lamp powers due to the high reflectivity of Al. Yet because of the long rapid thermal anneal (RTA) times (~1 sec) illumination from either side resulted in comparable melt profiles. By melting of Al deposited on several substrates we found that molten Al did not wet TiN. It seemed to wet W:Ti, however, along with a metallurgical reaction between Al, W and Si.