Modeling of a Schottky Diode in CMOS Process with a Flexible “Open-Through” On-Chip De-embedding Method

Modeling of Schottky diodes in the CMOS process is a key step in ultra-high frequency (UHF) radio frequency identification (RFID) transponder designs. Accurate Schottky diode models need both DC and RF models. Conventional DC models of the Schottky diode fail to predict the forward leakage current, which is crucial for precise simulation results. This paper presents a Schottky diode model with an additional diode which gives the correct forward leakage current. The RF model of the Schottky diode is constructed based on the measured S-parameters. Then, an on-chip de-embedding process is needed to remove the parasitics due to the pads and interconnection lines in the S-parameter test. A flexible “open-through” on-chip de-embedding method is proposed which only requires an “open” dummy and a “through” dummy, with all the lumped and distributed parasitics equivalent to two-port networks to give sufficient high-frequency de-embedding accuracy. By the help of this de-embedding method and the new DC model, the accuracy of the established diode model could be guaranteed. The Schottky diode model is verified by comparison between measurements and simulations and successfully applied to an RFID transponder design.