Polymethyl Methacrylate Passivation of Carbon Nanotube Field-Effect Transistors: Novel Self-Aligned Process and Effect on Device Transfer Characteristic Hysteresis

Abstract

Hysteresis in carbon nanotube field-effect transistors (CNTFETs) is an important issue that should be solved in the face of an integration in the complementary metal oxide semiconductor (CMOS) technology. One possible way is the passivation of the devices with poly(methyl methacrylate) (PMMA). In this work, PMMA-passivated CNTFETs are produced with a novel self-aligned fabrication process. The nanotubes are grown in-situ by chemical vapor deposition over the wafer surface so that no complex manipulations are required. The unique step of lithography avoids misalignment. With this suitable fabrication process, more than 6000 passivated transistors have recently been fabricated very easily in our institute. The devices are working like p-type MOSFET with on/off ratios of up to several 106, are fully functional even at ultralow supply voltages (e.g., 400 mV drain voltage, -3 to 3 V gate voltages) and show reduced hysteresis effects (e.g., 580 mV at Ids of 10-8 A).