PECVD grown silicon nitride ultra-thin films for CNTFETs

As-fabricated carbon nanotube field effect transistors (CNTFLTs) exhibit p-type nature. In this work, silicon nitride (SiNx) films are deposited on CNTs to realize n-type CNTELTs. This method of fabricating n-type CNTELTs is advantageous as SiNx film serves both as a passivation layer and as a top-gate dielectric. There has been extensive work done on SiNx passivation phenomena previously, but very few have investigated the properties of ultra-thin SiNx films with thickness less than 20 nm. In this work, the ultra-thin SiNx films are deposited using plasma enhanced chemical vapor deposition (PECVD) method. This paper discusses the systematic investigation of the effect of PECVD process parameters such as flow rates of precursor gasses (NH3, SiH4), power of electrodes and deposition temperature on the properties of SiNx films such as refractive index, dielectric constant and stoichiometry. The quality of the SiNx thin films obtained is comparable with several reports that have investigated thicker films Using these ultra-thin SiNx films, we implement a CNTELT based logic inverter. The results indicate that ultra-thin films of SiNx have great potential in future transistor technology.