Chip embedding technology for power applications

During the past decade embedding of semiconductor chips into printed circuit board structures evolved from a research topic to volume production. The paper will briefly describe this development and categorise today's embedding technologies. First modules with embedded chips are in production in Asia, mainly for telecom and computer applications. In Europe embedding has gained a strong interest for power modules, especially in automotive applications. Main drivers are the capability for compact and thin packaging, the high reliability and cost saving potential. In a number of European cooperation projects with partners from industry and research, embedding of power chips, like IGBTS and power MOSFET, is pushed. In this paper current achievements of these projects will be shown, especially examples of realised devices and their characteristics. The dominating technology for power chip embedding is a face-up technology. Chips are bonded with their backside (drain contact) to a Cu substrate using highly conductive adhesive or solder. Then Chips are embedded by vacuum lamination of prepreg or RCC (resin coated copper) layers. Via holes to the top contacts (gate and source) are formed by laser drilling. The vias are metallised using conventional Cu plating. Finally conductor structures are etched in the top Cu layer, finalising the circuit. Details will be given about device manufacturing, related yield issues and strategies to overcome them. Finally scenarios for the implementation of embedding technology and concepts for future applications will be discussed.