Properties Of SiNx Films Research Articles

PECVD grown silicon nitride ultra-thin films for CNTFETs

As-fabricated carbon nanotube field effect transistors (CNTFETs) exhibit p-type nature. In this work, silicon nitride (SiNx) films are deposited on CNTs to realize n-type CNTFETs. This method of fabricating n-type CNTFETs 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 CNTFET based logic inverter. The results indicate that ultra-thin films of SiNx have great potential in future transistor technology.

Dependence of Mechanical Stresses in Silicon Nitride Films on the Mode of Plasma-Enhanced Chemical Vapor Deposition

Films of silicon nitride SiNx, obtained by plasma-enhanced chemical vapor deposition from the monosilane SiH4 and ammonia NH3 gases, are widely used in microelectronics and micro- and nanoelectromechanical systems. Residual mechanical stresses and film composition are important characteristics for many applications. The properties of SiNx films, particularly mechanical stresses and composition, depend largely on the conditions of production, e.g., the ratio of the reacting gas flow rates, the composition of the gas mixture, the power and frequency of the plasma generator, and the temperature and pressure during deposition. Despite the great volume of works on the subject, data regarding the dependence of the properties and composition of SiNx films on the conditions of production remain sparse. This work considers the effect the ratio of the reacting gas flow rates has on the mechanical stresses and composition of silicon nitride films SiNx obtained by plasma-enhanced chemical vapor deposition from gaseous mixtures of SiH4 monosilane and NH3 ammonia using low-frequency plasma. It is found that when the ratio of the gas flow rates of SiH4 and NH3 is raised from 0.016 to 0.25, the compressive mechanical stresses are reduced by 31%, the stoichiometric coefficient falls from 1.40 to 1.20, the refractive index rises from 1.91 to 2.08, the concentration of N–H bonds is reduced by a factor of 7.4, the concentration of Si–H bonds grows by a factor of 8.7, and the concentration of hydrogen atoms is reduced by a factor of 1.5. These results can be used for the controlled production of SiNx films with such specified characteristics as residual mechanical stresses, refractive index, stoichiometric coefficient, and the concentration of hydrogen-containing bonds.

Influences of substrate temperature on crystalline characteristics and mechanical properties of SiNx films deposited by microwave electron cyclotron resonance magnetron sputtering

Hydrogen-free SiNx films were deposited at substrate temperature ranging from room temperature to 700℃ by microwave electron cyclotron resonance plasma enhanced unbalanced magnetron sputtering system. We have studied the influence of substrate temperature on the structural characteristics of deposited films including growth rate, microstructure, grain size, and hardness by using transmission electron microscopy, Fourier-transform infrared spectroscopy, and nano-indentation. The results indicate that the films deposited at room temperature are amorphous, and α-Si3N4 grains with random epitaxial sizes appear when substrate temperature is higher than 300℃. The α-Si3N4 grain size increases with substrate temperature up to 620℃, and then decreases at 700℃. At 700℃, the grains have uniform epitaxial sizes, and value of the film hardness reaches the maximum (36.7GPa).

DIELECTRIC PROPERTIES OF SiNx FILMS DEPOSITED AT LOW TEMPERATURE

The dielectric properties of SiNx films,which were deposited at low temperature by microwave electron cyclotron resonance plasma chemical vapor deposition,have been investigated.The frequency dependence of ε′and ε″ have two kinds of power-law dependence in the frequency range of 5—106Hz due to the fractal structure in nanometer-sized amorphous films.The relationship between ε′and ωn－11 with n1=0.82—0.88- due to electron hopping are obtained at low frequency region,and the relationship between ε′ and- ωn－12 with n2=0.05 due to the fractal structure conduction are- obtained at high frequency region.