Dielectric Properties and RF characterisitics of Bismuth-Zinc-Niobium Thin Films for Embedded Capacitor in PCB

The BZN thin films on copper clad laminate substrate by RF sputtering were studied for embedded capacitor application in PCB. The deposition was performed without substrate heating and the deposited films are composed of an amorphous phase. The dielectric properties of BZN thin films were dependent on the deposition parameters. The dielectric constant of the BZN thin films decreases with oxygen addition from 113 to 30. However, the leakage characteristics were improved by the oxygen addition, probably due to the removal of metallic bismuth in the film. By optimizing the lyaer structure, amorphous BZN thin film provides a capacitance density as high as 280 nF/cm². Dielectric loss was below 1.5% and the capacitor shows excellent leakage current behavior. In addition, thin film embedded capacitor showed much lower impedance at high frequencies above ~ 150 MHz when compared with LICC and IDC.