Characterization Of Silicon Nitride Films Research Articles

Characteristic Study of Silicon Nitride Films Deposited by LPCVD and PECVD

This paper analyzes and compares the characteristics of silicon nitride films deposited by low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD), with special attention to the hydrogenation and chemical composition of silicon nitride films. Three different LPCVD processes at various DCS and NH3 gas flow rates and deposition temperatures, together with PECVD using SiH4 and NH3 and ICP CVD using SiH4 and N2, were compared. The silicon nitride film deposition rate decreases with an increasing NH3/DCS ratio in LPCVD, which also leads to an increase in the refractive index and a decrease in the residual stress in the film. There is nearly no hydrogen incorporated in the LPCVD films, which differs from PECVD and ICP CVD that show significant Si-H and N-H bonds. The chemical composition of silicon nitride films is mostly Si-rich, except for the LPCVD process at high NH3/DCS ratio with near stoichiometric chemistry.

A study of deposition conditions on charging properties of PECVD silicon nitride films for MEMS capacitive switches

The present paper aims to provide a better insight to the electrical characteristics of silicon nitride films that have been deposited with PECVD method under different conditions. The effect of film thickness, substrate temperature and the frequency that produces the plasma in PECVD method on the dielectric charging phenomenon in silicon nitride films has been investigated with the aid of thermally stimulated depolarization currents (TSDC) and Kelvin Probe (KP) techniques. The results indicate that the decrease of film thickness and substrate temperature as well as the deposition at high frequency plasma (13.56MHz) seems to produce silicon nitride films that are less prone to dielectric charging and thus better candidates for MEMS capacitive switches.

Characteristics of Silicon Nitride Films Deposited by Cat-CVD at a Low Temperature (100 ℃)

Silicon nitride (SiNx) films for use as gate dielectric layers in thin-film transistors (TFTs) were deposited by catalytic chemical vapor deposition (Cat-CVD) at a low substrate temperature (100 ºC). Filament geometry, spacing between the filament and the substrate, and process pressure were optimized to deposit reliable dielectric films at 100 ºC. Silane (SiH4), ammonia (NH3) and hydrogen (H2) were used as source gases, and the flow ratios of NH3 / SiH4 and H2 / SiH4 were varied from 10 to 60 and from 20 to 200, respectively. An in-situ chemical annealing was performed by using H2 during the deposition process. As a result, SiNx films having a composition close to stoichiometry, having an electrical resistivity of 1012 ohm∙cm and a breakdown field strength of 7 MV/cm, were obtained. These films are believed to be applicable to TFTs on plastic substrates.

Characteristics of Silicon Nitride Films Deposited by Cat-CVD at a Low Temperature (100 °)

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Infrared ellipsometric characterization of silicon nitride films on textured Si photovoltaic cells

AbstractWe present an infrared spectroscopic ellipsometry investigation of SixNyfilms deposited on textured Si substrates employed for photovoltaic cells. A multiple-sample data analysis scheme is used in order to determine the SixNydielectric function and thickness parameters regardless of the surface morphology of the substrate. We observe changes in the dielectric function of the silicon nitride film which suggest variations in the chemical composition of the films depending on the substrate morphology.

Reliability of Silicon Nitride Gate Dielectric in Vertical Thin-Film Transistors

AbstractIn this work, we have conducted a systematic investigation of leakage current and electrical breakdown of plasma enhanced chemical vapor deposited (PECVD) silicon nitride, both for planar films and deposited films on the vertical sidewall for the application of the vertical thin film transistors. The thickness evolution of physical properties and electrical characteristics of silicon nitride films in the range of 50 to 300 nm are investigated. Electrical breakdown strength for 150-300nm thick films was approximately 7 MV/cm, whereas the value dropped to ~3MV/cm for 50nm thick films deposited under the same process conditions. It is shown that the early failure of the thin nitride is accompanied by the increase of the pinholes number. For the vertical thin film transistors, the experimental result shows the reliability and leakage current of the gate dielectric depends on the step coverage of the silicon nitride film on the vertical sidewall.

Characterization of silicon nitride films prepared by MW-ECR magnetron sputtering

Hydrogen-free silicon nitride films were deposited at room temperature by microw ave electron cyclotron resonance (ECR) plasma source enhanced unbalanced magnetr on sputtering system. Fourier-transform infrared spectroscopy and X-ray photoele ctron spectroscopy were used to study the bond type, the change of bond structur es, and the stoichiometry of the silicon nitride films. Atomic-force microscopy and nano-indentation were used to study the morphological features and mechanica l characteristics of the films. The results indicate that the structure and char acteristics of the films deposited by this technique depend strongly on the dens ity of sputtered Si in plasma and the films deposited at 4 sccm N2 fl ow show excellent stoichiometry and properties.

Investigations of silicon nitride layers deposited in pulsed microwave generated ammonia–silane plasmas

Pulsed plasmas are of increasing importance for applications of high rate film deposition or etching processes under low plasma induced damage. The deposition rate and the characteristics of silicon nitride films can be strongly influenced by a suitable choice of the pulse parameters like pulse/pause ratio, the pulse frequency and the composition of the reactants. The intention of these investigations is to optimise the deposition of silicon nitride films in pulsed microwave plasmas.

Growth and characterization of silicon nitride films for optoelectronics applications

Abstract Silicon nitride (Si3N4) films have been deposited by thermal-CVD system and characterized by the ellipsometry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The present paper reports the effect of deposition temperature on the physical and optical properties of deposited Si3N4 films. The stress of the film has been observed to be tensile in nature and it is found to be decreased by increasing the deposition temperature through ellipsometric study. The increase in refractive index of the film has been observed with increasing deposition temperature. The Si–H, N–H and Si–N–Si stretching characteristic peaks of Si3N4 films have been observed with significant intensities by using FTIR spectroscopy. The peak positions of Si–N–Si stretching absorption band and the corresponding full width at half maxima (FWHM) have also been analyzed. The FWHM observed to be increasing on corresponding increase in the deposition temperature, which indicates the improvement in the deposited films quality. However, films deposited in the temperature range of 780–850 °C, have some amount of H contents. The total H concentration in the films decreases with corresponding increase in deposition temperature, which reveals that the densification of deposited films increases on increasing the deposition temperature. The SEM and EDAX have been used to carry the morphological and compositional analysis of the deposited films, respectively.

High rate deposition of silicon nitride films by APCVD

Silicon nitride films have been prepared by atmospheric pressure chemical vapor deposition (APCVD) on moving glass substrates from a gas mixture of monosilane, ammonia and nitrogen. The CVD reactor system used in this work is similar to those used in APCVD during a float glass production process (on-line CVD). At the substrate temperature of 830 °C, we prepared silicon nitride films and the deposition rate was over 10 nm/s. The deposition rates measured are not high enough at the temperatures typical of most on-line processes (650–750 °C). The deposition rate and the characteristics of silicon nitride films have been investigated using ellipsometry, X-ray photoemission spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). The obtained film is transparent and the refractive index at the wavelength of 550 nm is 1.90–1.97. The film composition depends on the ratio of NH 3 to SiH 4 in the source gas and the hydrogen concentration is approximately 15%. It seems that hydrogen atoms incorporated in the film affect properties of the films.

Growth Processes and Electrical Characteristics of Silicon Nitride Films Formed on Si(100) by Radical Nitrogen

We have investigated nitridation processes on clean Si(100)-2×1 surfaces and the electrical characteristics of metal-insulator-semiconductor (MIS) capacitors with nitride films formed by radical nitrogen. The radical nitrogen exposure to Si surfaces at 500°C initially causes both nitridation of Si and local detachment reactions on the surface. It is found from scanning tunneling microscopy and scanning tunneling spectroscopy that the nitridation proceeds in a layer-by-layer manner in which a continuous film is formed by the coalescence of two-dimensional islands. At nitride thicknesses above 0.6 nm, the nitride film is homogeneously formed over the entire surface. The MIS capacitor with a 5.4-nm-thick nitride film formed by radical nitrogen shows low hysteresis of less than 0.1 V and low leakage current density. These electrical properties indicate that the nitride films formed by radical nitrogen are applicable to gate insulators.

Growth and characterization of silicon nitride films on various underlying materials

Characteristics of silicon nitride (SiNx:H) films, grown by plasma enhanced chemical vapor deposition (PECVD) on various metals such as Ta, IrMn, NiFe, Cu, and CoFe at various temperatures down to 100 °C, were studied using measurements of BHF etch rate, surface roughness and Auger electron spectroscopy (AES). The results were compared with those obtained for SiNx:H films on Si. The deposition rate of SiNx:H films increased slightly as deposition temperature decreased, and showed a weak dependence on the underlying materials. The surface of the nitride films deposited on all underlying materials at lower temperatures (below 150 °C) became rougher. In particular, a bubble-like surface was observed on the nitride film deposited on NiFe at 100 °C. At higher deposition temperatures (above 200 °C), SiNx:H films on all the above metals had small RMS values, except for films on Cu which cracked at 250 °C. BHF (10:1) etch rate increased dramatically for nitride films deposited below 150 °C. For different underlying films, the BHF etch rate was quite different, but exhibited the same trend with decrease in deposition temperature. AES measurements showed that Si and N concentrations in the SiNx:H films were only slightly different for the various deposition temperatures and underlying materials. AES depth profile of nitride films indicated that both surface O content and the depth of oxygen penetrating into SiNx:H increased for low temperature-deposited films. However, there was no observed oxygen signal from within the films, even for films deposited at 100 °C, and both Si and N concentrations were uniform throughout the film.

The characterization of silicon nitride films by contactless transient photoconductivity measurements

It is shown by non-invasive photoconductivity measurements that the coating of Si wafers by silicon nitride films leads to the increase of number of excess charge carriers generated in the silicon substrate by visible light due to the antireflection properties of the films. The silicon surface is electrically passivated by the deposition of these films on top of it.

Remote plasma-enhanced CVD of silicon nitride films: effects of diluting nitrogen with argon. Part I: effect on nitrogen plasma parameters studied by emission spectroscopy

In a series of two papers we describe the effect of argon dilution of the nitrogen passed through the RF discharge region on the plasma composition, growth rate and some characteristics of silicon nitride films deposited by remove PECVD. In this part we report the results of an emission spectroscopic study of the plasma obtained in an SiH4–N2–Ar mixture. It is shown that argon in metastable electronic excited states plays an important role during the RPECVD of silicon nitride films by providing a high concentration of atomic nitrogen which is necessary for the promotion of film growth. In Part II the influence of argon dilution on the growth rate, composition and some properties of silicon nitride films deposited by capacitively and inductively coupled remote PECVD is discussed. © 1998 John Wiley & Sons, Ltd.

Remote plasma‐enhanced CVD of silicon nitride films: effects of diluting nitrogen with argon. Part I: effect on nitrogen plasma parameters studied by emission spectroscopy

In a series of two papers we describe the effect of argon dilution of the nitrogen passed through the RF discharge region on the plasma composition, growth rate and some characteristics of silicon nitride films deposited by remove PECVD. In this part we report the results of an emission spectroscopic study of the plasma obtained in an SiH4–N2–Ar mixture. It is shown that argon in metastable electronic excited states plays an important role during the RPECVD of silicon nitride films by providing a high concentration of atomic nitrogen which is necessary for the promotion of film growth. In Part II the influence of argon dilution on the growth rate, composition and some properties of silicon nitride films deposited by capacitively and inductively coupled remote PECVD is discussed. © 1998 John Wiley & Sons, Ltd.

Electronic properties of silicon-nitride films deposited by low-energy ion-beam bombardment

Ultrathin silicon-nitride films have been synthesized on silicon substrates by low-energy nitrogen-ionbeam bombardment. The thicknesses of the obtained films are found to increase slightly with the duration of bombardment. Capacitance-voltage and current-voltage characteristics of silicon-nitride films prepared at different bombarding times show that the density of damages, charges in the films and interface states, the capacitance of the obtained ultrathin silicon-nitride films, the flat-band capacitance and the flat-band voltage increase with the duration of the bombarding process. The results of these analyses suggest a short bombarding processing for such a silicon-nitridation technique proposed here.

Plasma-enhanced silicon nitride deposition for thin film transistor applications

The characteristics of silicon nitride films deposited in a multiprocess reactor have been investigated to determine the most suitable layers for dielectric and passivation applications. Process parameters such as rf power, temperature and gas flow ratios have been varied to control the stoichiometry of the films, and associated parameters such as refractive index, BHF etch rate, relative permittivity and breakdown field. Using these results, silicon nitride films with favourable characteristics have been deposited and used successfully in thin film transistors.

Optical characterization of silicon nitride films deposited by ECR-CVD

Optical properties (refractive index and band gap) and atomic bonding structure of silicon nitride films deposited at room temperature by the ECR-CVD method are analysed as a function of two main production parameters: microwave power (50–200W) and N 2/SiH 4 ratio (1.6–9). Transmission and reflection measurements in the UV-VIS-NIR region show that optical properties of the films are strongly dependent on the deposition conditions: refractive index values from 2.8 to 1.7 and band gap values in the 2.1–5.3 eV range are obtained depending on deposition conditions. The FTIR spectra analysis show that silicon-rich films are obtained at low microwave powers and low N 2/SiH 4 ratios, whereas films with oxygen contamination are deposited at high powers for every flow ratios. Close to stoichiometric silicon nitride films are obtained at 100 W with N 2/SiH 4 ratios higher than 5.

Influence of Surface Preparation Prior to Thermal Nitridation on the Electrical Characteristics of Silicon Nitride Films Deposited on Polycrystalline Silicon Films

ABSTRACTRapid thermal nitridation of the polycrystalline silicon film prior to the deposition of the silicon nitride dielectric film has been shown to be very effective in improving the dielectric characteristics for thin films. The changes at the polysilicon-silicon nitride interface has been further investigated using an in-situ clean process. This pre-treatment reduces the oxygen levels at the interface and improves the time dependent dielectric breakdown. The leakage current increases slightly due to the thinning of the silicon dioxide film at the interface.

Growth and characterization of silicon nitride films produced by remote microwave plasma chemical vapor deposition

Films of silicon nitride have been grown in an ultrahigh vacuum system by the reaction of silane with nitrogen remotely excited in a microwave plasma at pressures in the range 0.1–0.9 Torr with substrate temperatures in the range 70–350 °C. Growth rates have been determined as a function of silane–nitrogen flow ratio, pressure, microwave power, and substrate temperature in order to give some insight into the growth mechanism. Results indicate that the rate of film deposition is governed by the arrival rate of active nitrogen species at the surface. The films have been characterized by 15N nuclear reaction profiling and Rutherford backscattering analysis to determine the hydrogen, silicon, and nitrogen contents. Hydrogen contents are comparable to those obtained with parallel-plate plasma enhanced chemical vapor deposition reactors while near stoichiometric, nitrogen rich films can be obtained over a wide range of deposition parameters. Floating double probe measurements used to obtain the electron temperatures and ion densities verify that substrate bombardment by charged or energetic particles is not a factor in the growth of these films.