Top-gated n-type Carbon Nanotube Field Effect Transistors using SiN_x dielectric for Logic Circuit Applications

Semiconducting single walled carbon nanotubes (CNTs) are considered to be one of the best alternates to Silicon particularly beyond 10 nm node transistor technology. There have been reports demonstrating CNTFET complementary (using both p- and n-FETs) circuits. Most of the reports on CNT based complementary circuits involved fabrication of n-type CNTFETs using rare earth metals for source/drain contacts. This approach may not be suitable for large scale manufacturing. In this work we have fabricated top-gated n-type solution-processed CNTFETs using Silicon Nitride (SiN_x) as gate dielectric and evaluated their performance for logic circuit applications. The n-CNTFETs are contacted (source/drain) using regular metals such as Palladium. SiN_x thin film is deposited over CNTs using low temperature Plasma Enhanced Chemical Vapor Deposition (PECVD) to realize air-stable n-CNTFETs. The SiN_x film serves both as passivation layer and gate dielectric. We have studied the effect of SiN_x film thickness on the performance of n-CNTFETs. Using the top-gated n-CNTFETs (with an Effective Oxide Thickness of ~10 nm), we have demonstrated a logic inverter circuit. This approach to fabricate top-gated n-CNTFET logic circuits is CMOS compatible and is suitable for large scale manufacturing.