Power Trench MOSFET Devices on Metal Substrates

Power trench MOSFET devices have been accomplished on Cu substrates using a novel silicon-on-metal (SOM) technology. This technology transfers silicon trench MOSFET device layers from SOI wafers to metal substrates. The prototype 30-V (drain-to-source voltage) n-channel SOM device with a pitch of 2.5 mum comprises a 5-mum device layer and an electroplated Cu substrate. These devices are the first of their kind exhibiting a negligible substrate drain contribution to their specific Rdson and have a specific Rdson of 0.198 mOmegaldrcm² at a gate voltage of 10 V. This specific Rdson is 38% smaller than that of the same device on the silicon substrate. The dc-dc converter with SOM devices shows 11% reduction in device power loss and an energy efficiency of about 2% higher than with the same Si-based devices. The operating temperature of the SOM die in the converter is also 9degC lower than the Si-based die. The ldquocoolerrdquo SOM device is due to primarily improved energy efficiency. The transient thermal resistance of the SOM device is 20degC/W, which is less than half of 57.5degC/W for the Si-based device at a pulse duration of 10 s.