Investigation of Low Loss and High Reliability Encapsulation Technology in Large-Area, High-Power Semiconductor Devices

In order to realize uniform and low contact resistance in the low mounting force region for large-area, high-power semiconductor devices, the effects of hardness and surface cleanliness of metal sheets inserted between an Al cathode and Mo internal electrode on the contact resistance were investigated as a function of mounting force. Contact resistance was lowered with increasing cleanliness and decreasing hardness of the inserted sheet for all values of the mounting force. A new process was developed in which an Ag-plated Mo sheet is heat-treated at 573 K for 15 min in air. It was confirmed that devices with the new Ag-plated Mo sheet have efficient long form reliability. The contact resistance and its dependence on the mounting force of the devices using this sheet are of the same level as those of an Ag-sputtered Mo sheet and an Ag sheet.