PWB compatible high value integral capacitors by MOCVD

Abstract

The 1998 National Electronics Manufacturing Technology Roadmap indicates that a capacitance density of ∼50 nF cm−2 will be required in 2001 for successful implementation of integral passive technology in the microelectronics packaging industries. Higher permittivity polymer/ceramic nanocomposites have been proven to be a viable option for integral capacitors on printed wiring boards (PWB). Although the nanocomposite materials are in their developmental stage, it is unlikely that this materials system could meet such high capacitance needs and still utilize a large area manufacturable process. In this study, an alternative metal organic chemical vapor deposition (MOCVD) technique has been implemented to deposit TiO2 thin film dielectrics at temperatures below 180 °C with higher capacitance densities. Two different metal-dielectric-metal type parallel plate capacitor structures have been fabricated on silicon and PWB substrates for relatively high frequency (45 MHz–1 GHz) and low frequency (100 Hz–1 MHz) characterization. Copper was used as the ground and upper electrodes with a 10 nm Cr adhesion layer between the dielectric and the electrodes. Capacitance was measured using a Keithley LCZ meter and a HP4194 impedance gain-phase analzer at the lower frequency range. Specific capacitance as high as 200 nF cm−2 was achieved at 1 MHz from devices built on silicon substrates and at 100 kHz from devices on PWB substrates. For the first time, thin film TiO2 on PWB substrates is reported at temperatures below 180 °C using MOCVD.