AN EFFECTIVE PASSIVATION FILM STACK FOR THIN FILM BST CAPACITORS

ABSTRACT

Thin film voltage tunable ferroelectric capacitors on various substrates are promising for use in high power microwave and other RF systems. Benefits of ferroelectric capacitors include miniaturization and integration with other passive devices.

Commercialization of ferroelectric components requires compliance with certain industry standards for reliability. For ferroelectric capacitors the requirement to pass the THB test requires a silicon nitride layer in the back end of the process (after interconnect metalization). However the nitride layer deposition process results in a drastic increase in the leakage of the BST capacitors. This effect is attributed to the exposure of the ferroelectric material to atomic hydrogen which is a by-product of the PECVD deposition process.

This paper presents results of different passivation materials for ferroelectric capacitors and for a barrier layer which preserves the performance of ferroelectric capacitors during a PECVD nitride deposition. This allows qualification of ferroelectric capacitors to industry reliability standards.

Keywords:

• BST
• ferroelectricity
• reliability
• hermetic passivation

ACKNOWLEDGMENTS

The authors would like to thank Shirley Lavigne and Carol Lee-Wood for fabrication of the BST capacitor wafers and Norma Gartrell for her assistance in packaging the devices for reliability testing.