ALUMINUM NITRIDE - AN ALTERNATIVE CERAMIC SUBSTRATE FOR HIGH-POWER APPLICATIONS IN MICROCIRCUITS

Nonmetallic inorganic materials having a high thermal conductivity are reviewed and their usefulness as a substrate material is studied. Detailed information is presented on the properties of aluminum nitride (AlN) a newly developed ceramic substrate material which, among the inorganic materials reviewed, seems to present an almost ideal solution to the requirements for packaging high-power and large-size silicon chips. By suitable powder technological processing, an AlN ceramic was produced with a thermal conductivity of about 140 to 170 W/mK, which is about one half of the theoretical value estimated for the defect-free single crystals. Another advantage of the newly developed material is its low coefficient of thermal expansion which, in the temperature range of interest (20-200 degree C), matches that of silicon very closely. It also has high electrical resistivity and a moderate dielectric loss.