Thermal dissipation improvement by new technology approach: study, development and characterization

Semiconductor manufacturing requires a silicon substrate to build devices on its front side. The wafer must be thick enough to ensure a stable support during the processing steps. Since the active region of a semiconductor device is limited at the substrate surface, there is a large unused material amount. The material excess causes heat increasing during the operation of the devices. Once the Frond End of Line is completed, the excess material must be removed. Nowadays, there are different thinning techniques adopted in order to reduce the thermal resistance. The thesis project idea is the thermal dissipation improvement with a different approach: instead of reducing the wafer thickness, the adopted technology is exploiting the excess material as a heat sink. The realization of this intrinsic heat sink is achieved by the developing of a suitable process flow, which involves the selective dry etching of the silicon bulk and the subsequent electrodeposition of thick copper. This new process flow offers the advantage of maintaining the wafer “self-support” and allow working with already existing technologies saving on both dedicated thinning technologies and handling technologies. Furthermore, this new approach permits the thermal resistance improvement of semiconductor devices if compared to the standard devices.