RF Model of BEOL Vertical Natural Capacitor (VNCAP) Fabricated by 45-nm RF CMOS Technology and Its Verification

Abstract

A radio-frequency equivalent circuit model for the symmetric vertical natural capacitor (VNCAP) in a 45 nm low-standby-power CMOS process is presented. The average effective capacitance density of 2.24 fF/ mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is obtained from VNCAPs of 1 times (M1 - M5) + 2 times (M6 - M7) metal-layer configuration after the open-short de-embedding procedure. The proposed model consists of main series capacitance network and lossy substrate network. The accuracy of the VNCAP model is verified S-parameters, effective capacitance C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> , and quality factor (Q) up to 15 GHz. The proposed model can accurately describe the frequency characteristics of S-parameters, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> , and Q-factor up to 15 GHz for VNCAPs with different widths and lengths.