Miniaturized 6-Bit Phase-Change Capacitor Bank with Improved Self-Resonance Frequency and $Q$

Abstract

This paper reports a 6-bit capacitor bank developed using metal-insulator-metal (MIM) capacitors with enhanced self-resonance frequency (SRF) and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex> -factor. An easy to implement design optimization technique is discussed to improve the SRF and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex> of high frequency MIM capacitors. Experimental data is shown for two MIM capacitors fabricated on high resistivity silicon substrate with silicon nitride as a dielectric layer. The optimized capacitors exhibit up to 45% improved SRF and up to 22% enhanced Q-factor in comparison with standards MIM designs. The capacitor bank utilizes six latching phase change material (PCM) germanium telluride (GeTe)-based RF series switches, monolithically integrated with six MIM capacitors having improved SRF. The capacitor bank measures only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.23\ \text{mm}\times 0.27\ \text{mm}$</tex> in size, making it a highly miniaturized and versatile switched capacitor bank for integrating with numerous RF circuits. Experimental data is compared with that of standard MIM capacitor-based capacitor bank. The optimized MIM based capacitor bank provides additional 3 GHz operating bandwidth compared to the standard MIM based capacitor bank.