Low-temperature sintered nanoscale silver as a novel semiconductor device-metallized substrate interconnect material

A nanoscale silver paste containing 30-nm silver particles that can be sintered at 280 degrees C was made for interconnecting semiconductor devices. Sintering of the paste produced a microstructure containing inicrometer-size porosity and a relative density of around 80%. Electrical and thermal conductivities of around 2.6 x 10(5) (Omega . cm)(-1) and 2.4 W/K-cm, respectively, were obtained, which are much higher than those of the solder alloys that are currently used for die attachment and/or flip-chip interconnection of power semiconductor devices. The sintered porous silver had an apparent elastic modulus of about 9 GPa, which is substantially lower than that of bulk silver, as well as most solder materials. The lower elastic modulus of the porous silver may be beneficial in achieving a more reliable joint between the device and substrate because of increased compliance that can better accommodate stress arising from thermal expansion mismatch.