Tantalum oxide dielectric for embedded capacitor applications

In many portable electronic devices, passive components, such as capacitors, usually outnumber active components. As such, in order to improve the packaging density of these portable electronic devices, it is desirable to remove the discrete capacitors and embed them in their packaging substrates. Embedded capacitors not only have lower parasitics, but they usually have a reduced form factor compared to surface mounted chip capacitors. In this work, tantalum oxide was investigated as the dielectric for embedded capacitors in flexible, polymeric high density packaging substrates. Both sputter-deposited and anodized tantalum oxide dielectrics for embedded capacitors were characterized. Their dielectric properties and conduction mechanisms were investigated. The capacitance of the tantalum oxide capacitors is essentially constant up to 1 GHz. Both sputter-deposited and anodized tantalum oxide films exhibit an ionic conduction mechanism. Their ionic conduction energies are found to be linearly dependent on the applied electric field