Tantalum Oxide Thin Films for Embedded Capacitors: Using Pulsed DC Reactive Sputtering
Embedded capacitor technology, where thin film capacitors are integrated at on-chip and/or off-chip levels, offers high packaging densities and improved electrical performance at potentially reduced costs of capacitor fabrication and integration. This research explores and establishes the leverages of using thin film embedded capacitors over currently used surface mount discrete capacitors. In particular, this work focuses on developing pulsed dc reactively sputtered tantalum oxide (Ta2O5) thin film capacitors for IC chips and packages. A design space for breakdown voltage and capacitance density of planar capacitors is established, with film thickness and material dielectric constant as parameters. The validity of the developed design space is experimentally verified with Ta2O5 thin films over a wide range of film thickness. An experimentally verified analytical model for pulsed dc reactive sputtering of Ta2O5 films is described and evaluated. Various processing and integration challenges in depositing thin films using reactive sputtering and their effects on electrical performance of thin-film capacitors are discussed.