L.M. Zambov

Optical, electrical and mechanical properties of nitrogen-rich carbon nitride films deposited by inductively coupled plasma chemical vapor deposition

An inductively coupled plasma utilizing chemical transport reactions has been used to deposit thin carbon nitride films with a high nitrogen content [N/(C+N) of approximately 0.5 or higher]. We report on the characterization of the application relevant properties of these films, especially the optical (refractive index, transmission), electrical (dielectric constant, resistivity) and mechanical characteristics (stress, hardness, wear resistance). The refractive index is in the order of 1.5–1.8 depending on the deposition conditions; furthermore, the films are highly transmitting for wavelengths above 600 nm. C–V curves indicate the insulating character of the CNx films which was confirmed by I–V measurements yielding resistivities up to 1011 Ω cm at room temperature. The layers possess marginal stress as measured by the bending method on silicon cantilevers. The hardness is in the range of 1 GPa, and a friction coefficient of 0.6 was determined by ball-on-disc tests against stainless steel balls. The investigations showed that these films may be suited especially for optical and electrical applications. Finally, we correlate the films characteristics with the composition and structure of the coatings.

The effect of d.c. substrate bias on the properties of nitrogen-rich CNx films

The influence of d.c. substrate bias on the properties of nitrogen-rich CNx films deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) utilizing transport reactions has been investigated. The film forming species are CN and/or (CN)2 generated by the interaction of the atomic nitrogen from the ICP with a solid pure carbon mesh; they are deposited on the substrate in the presence of nitrogen species from the plasma. A study of the surface topography of the coatings by atomic force microscopy (AFM) shows that the average roughness slightly increases from below 1 nm without bias to 1.6 nm at −300 V. The deposition rate decreases by a factor of 1.3–1.5 (depending on the working pressure) with increasing the bias up to −300 V, mainly as a result of desorption of CN species from the substrate enhanced by the ion bombardment. The CNx films deposited with bias exhibit nitrogen atomic fraction N/(C+N) in the range of 50–60%, as revealed by surface and bulk techniques. The chemical bonding structure of the layers investigated by Fourier transform infrared (FTIR) spectroscopy showed only a marginal influence of the d.c. substrate bias. The increase of the refractive index n from 1.6 to 1.8 is probably due to slight densification of the films deposited with substrate biasing as a result of reduction of voids.

THIN CNX FILMS PREPARED BY VACUUM RAPID THERMAL ANNEALING

Abstract The properties of thin CNx layers prepared by rapid thermal annealing (RTA) are compared with CNxlayers obtained from N2 plasma treatment. Carbon films of 6000 A thickness were deposited by magnetron sputtering system on p-type silicon substrates. The samples were treated in an RTA system in N2 atmosphere at a temperature above 800C. Some of the samples were treated in an N2 plasma. The resulting CNx layers were analyzed by XPS (X-ray photoelectron spectroscopy) technique. The concentration of the incorporated nitrogen and carbon in the layer depths were analyzed by consecutive etching and measurement of the XPS spectra. This showed that maximum depth of incorporated nitrogen atoms in the carbon layer after 800C, 1 min RTA in N2 was about 100 A , while in the N2 plasma treated samples a nitrogen concentration of 6% was observed at 150 A . The electrical resistance of the layers rose with increase of the nitrogen concentration in the layers.

Design of Injection Feed Multiwafer Low‐Pressure Chemical Vapor Deposition Reactors

A two-dimensional model has been developed for low-pressure chemical vapor deposition reactors with injection feeding of gas components. The classical methods for linear differential equations are applied to obtain analytical solutions of the model both with and without main gas flow in the system. Analysis of the model reveals a relationship between the reactor geometry and the process parameters for maintaining constant reagent concentration in the system. Injection design is determined by means of simulation study of definite deposition processes.