DIAMOND FILMS AS THERMAL CONDUCTORS AND ELECTRICAL INSULATORS APPLIED TO SEMICONDUCTOR POWER MODULES

Module technology, i.e. the integrated variety of power devices insulated to ground, has become the most successful technology for power devices. The sandwich structure of the module serves as both an electrical insulator and heat sink to remove the heat generated in the device. Typical heat fluxes of 200 W cm-2 through the chip-substrate interface make it necessary to develop modules with a lower thermal resistance than those available today. With the recent advances in diamond technology, diamond substrates which have unique heat conducting properties are now available. The application of diamond substrates as heat sinks for power dissipating devices is well known. Presented here is an application of diamond films in power device modules in combination with a new low temperature joining technology based purely on solid joining materials. The thermal behaviour of these modules was simulated. Following the simulations power device modules with a diamond film were produced. The thermal properties of the modules were investigated. The results are in good agreement with those of the simulations. It is demonstrated that diamond films together with an advanced joining technology provide a great improvement in thermal management compared with state-of-the-art technologies. For investigation of the electrical insulation as an important parameter for power modules measurements of the I-V characteristics of chemically vapour deposited diamond films were taken. The resistivity of the layers used in our experiments can be increased by an appropriate post-deposition treatment; however, it is still more than two orders of magnitude lower than typical values of alumina substrates. It is found that inhomogeneities possibly determine the electrical insulation properties of chemically vapour deposited diamond layers.