High temperature dielectric property of silicon nitride insulating substrate for next generation power module up to 350 degrees Celsius.

Recently, as power module tends to have higher output density, large-capacity and downsizing of the module are demanded. It also tends to operate at higher temperatures. From the above circumstances, evaluation of high temperature electrical properties of ceramic insulating substrates for application of next generation power module becomes important. However, there are very few reports on the high temperature insulation property of the ceramic insulating substrate. This paper presents dielectric properties (relative permittivity εr´, relative dielectric loss factor εr″ and AC conductivity σac) of ceramic insulating substrate consisting of Silicon Nitride (Si3N4) used for next generation power module up to high temperature of 350 °C. Besides, DC conductivity σdc are evaluated as a function of the temperature of the substrate, from which the activation energy Ea was calculated. Thus obtained results are discussed with the temperature dependence of the permittivity and ac conductivity considered. An attempt is also made to evaluate specific properties of the Si3N4 substrate by comparing with the dielectric properties of Aluminum Nitride (A1N) substrate.