Improvement of carbon nanotube-based field-effect transistors by cleaning and passivation

Ever since their discovery in 1991, carbon nanotubes are of great interest to the scientific community due to their outstanding optical, mechanical and electrical properties. Considering their impressive properties, as for instance the high current carrying capability and the possibility of ballistic charge transport, carbon nanotubes are a desired channel material in field-effect transistors, especially with respect to high frequency communication electronics. Thus, many scientific studies on CNT-based field-effect transistors have been published so far. But despite the successful verification of excellent individual electric key values, corresponding experiments are mostly performed under synthetic conditions (considering e.g. temperature or gas atmosphere), which are not realizable during realistic application scenarios. Furthermore, technologically relevant factors like homogeneity, reproducibility and yield of functioning devices are often subordinated to the achievement of a single electric record value. Hence, this work focuses on the development of a fabrication technology for carbon nanotube field-effect transistors, that takes those factors into account. Thereby, this work expands the state of the art by introduction and statistical assessment of two cleaning processes: a) wet chemical removal of surfactant residues (sodium dodecylsulfate) from CNTs, integrated using the dielectrophoretic approach, by investigation and comparison of four procedures (de-ionized water, HNO3, oDCB, Ethanol); b) the reduction of process-related substrate contaminations by application of an oxygen plasma. Beyond that, the passivation of the final, working devices is developed further, as their typical definition as diffusion barrier is expanded by the reduction of parasitic capacitances in the transistor. In this context, two so far barely considered materials, hydrogen silsesquioxane and Xdi-dcs, a polymer mixture of poly(vinylphenol) and polymethylsilsesquioxane, are investigated and assessed. The novelty of the Xdi-dcs mixture causes the necessity of fundamental considerations on controllable etching procedures and resulting adaptions of the technological fabrication sequence.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Chemnitz

Year

2020

Author dc:creator

• Tittmann-Otto, Jana

Contributors dc:contributor

• Schulz, Stefan E.
• Tegenkamp, Christoph
• Hermann, Sascha

• Carbon Nanotube
• Field-effect transistor
• Dielectrophoresis
• Transfer characteristics
• Hysteresis
• Surfactant
• Process contamination
• Plasma cleaning
• Passivation
• Kohlenstoffnanoröhren
• Feld-Effekt Transistoren
• Dielektrophorese
• Transferkennlinie
• Hysterese
• Tenside
• prozessinduzierte Kontaminationen
• plasmaunterstützte Reinigung
• Passivierung