Reconfigurable PCM GeTe-Based Latching 6-Bit Digital Switched Capacitor Bank

This paper reports the design, fabrication and characterization of a miniature RF phase change material (PCM) germanium telluride (GeTe) based 6-bit switched capacitor bank. The capacitor bank utilizes six latching PCM RF series switches, monolithically integrated with six metal-insulator-metal (MIM) capacitors, providing 64-states in a compact 0.5 mm × 0.5 mm package including the pads of the CPW input port and the control pads. The core measures only 0.23 mm × 0.27 mm making it a highly miniaturized and versatile switched capacitor bank for integrating with various RF circuits. Measured capacitance tuning range exhibits 34:1 at 2 GHz and 58:1 at 7 GHz with no self-resonance observed up to 7 GHz. The integrated RF PCM switches exhibit excellent RF performance with insertion loss lower than 0.2 dB and isolation better than 30 dB over 2 GHz to 7 GHz band. The proposed device is realized using seven-layer microfabrication process that includes a thermally conductive dielectric for efficient heat transportation. EM simulations and measurements demonstrate various states covering the capacitance range of 0.14 pF to 8 pF.