Sputter deposition of thin-film capacitors onto low temperature co-fired ceramic substrates

Single layer thin film capacitor structures were fabricated on the surface of low temperature co-fired ceramic (LTCC) substrates using sputter deposition. The capacitor structures had areas between ~10⁴ µm² to ~10⁶ µm² and featured ~200 nm Al or Pt electrodes with 150-1500 nm Al₂O₃ dielectric layers. Impedance analysis and current-voltage testing were carried out to determine the effect of electrode material and dielectric thickness upon capacitor performance. Capacitance values for devices with Al electrodes ranged from ~10 to ~700 pF, depending on capacitor area and dielectric thickness, and the fit to expected values was better than devices with Pt or mixed (one Al, one Pt) electrodes. Dielectric loss increased with increasing Al₂O₃ thickness, most likely due to cracking in thick (\u3e1 µm) sputtered films. All measured loss values for the sputter deposited Al₂O₃ (tan[lambda]~0.02) were greater than bulk Al₂O₃ (tan[lambda] ~0.001). Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were utilized to examine selected capacitor structures. Electron beam induced crystallization of amorphous Al₂O₃ was observed during the selected area diffraction (SAD) patterns. TEM examination and impedance analysis both confirm that functional capacitors with Al electrodes and 300 - 000 nm thick Al₂O₃ dielectric layers can be fabricated on LTCC substrates using sputter deposition --Abstract, page iv