Integrated tantalum pentoxide capacitors were successfully used to replace discrete CK05 (Mil Part Code) capacitors in multichip modules (MCM) for power electronic applications. The tantalum pentoxide capacitors were evaluated in-a Very High Density (VHD) power supply proposed for the Joint Strike Fighter (JSF) program and a 550 kHz, push-pull DC/DC switching converter. These embedded Al/Ta2O5/Al capacitors exceeded the requirements for a common Current Sense Module that was employed as a test vehicle. The capacitance tolerance was less than 10% and the dielectric strength was greater than 200% of the specified Vdc. After exposure to the 350 degreesC polyimide cure cycles, there was a reduction in leakage current of approximately an order of magnitude with only a 0.4 decrease in dielectric constant. Final leakage current on the test vehicle lot was less than 4e-15 A/cm2 at 5 volts. Two sizes of capacitors, 0.01uF and 100pF, were fabricated for the Current Sense Module. The 0.01uF embedded capacitors provided a 30% reduction in size compared to the discrete CK05 ceramic capacitors. The 100pF were nearly 10 times smaller. Furthermore, the thin profile (0.8 mum) of the embedded capacitors allowed them to be fabricated underneath the routing layers. In order to decrease the amount of area required for embedded passives, multilayer capacitors were also fabricated and tested. The multilayer capacitors in this study have a novel lead configuration which allows them to act as two separate capacitors connected in parallel. This unique approach can nearly double the capacitor value per square micron.
