Monolithic Heterogeneous Integration of BEOL Power Gating Transistors of Carbon Nanotube Networks with FEOL Si Ring Oscillator Circuits

High performance carbon nanotube (CNT) network transistors with on-resistance (R _on ) of <; 250 Ω are successfully integrated as back-end-of-the-line (BEOL) power gating devices onto Si CMOS wafers manufactured using 28-nm process technology. When the power supply is connected through the BEOL CNT network header array, the front-end-of-the-line (FEOL) Si ring oscillators (ROs) achieve a similar quiescent current (I _DDQ ) and have the comparable active power (P _ACTIVE ) consumption under the same operation frequency as compared to the operation without the power gating CNT transistors. The fabrication of CNT devices in the BEOL is verified to cause no performance degradation in the underlying FEOL Si CMOS devices. This study has successfully demonstrated heterogeneous integration of advanced Si logic circuits with low-cost and high-mobility CNT transistors in the BEOL fabricated at low, BEOL-compatible temperatures (250 °C).