Development of fabrication techniques for high-density integrated MIM capacitors in power conversion equipment

In portable electronic equipments, miniaturisation, cost, multi-functionalities and reliability are the main factors driving the power electronics industry. In this context, the realisation of all integrated high performance DC-DC micro-converters working at high frequencies (few MHz) is necessary. The passive components such as inductors, transformers and capacitors, are for the moment the bulkiest components and their integration on silicon substrate would constitute a real improvement in term of compactness and reliability of power converters. This paper deals with the fabrication of integrated capacitors realised on silicon using MEMS-type techniques. High capacitance density, low series resistance and inductance are sought. Structures using deep cavities etched in silicon were realised in order to increase the effective area of the capacitor's electrodes while minimising the area on the substrate. The development of micro-fabrication techniques such as Deep Reactive Ion Etching (DRIE) and doped-polysilicon deep trenches filling are presented. Some preliminary measurement on the fabricated capacitors with the developed processes show that high capacitance density (36 nF/mm 2 ) can be obtained.