Characterization Of Silicon Nitride Films Research Articles

Growth and characterization of silicon-nitride films by plasma-enhanced chemical vapor deposition

Thin films of silicon nitride were deposited on Si wafers by plasma-enhanced chemical vapor deposition (PECVD). For deposition we designed and made hot wall capacitively coupled PECVD equipment which has a radial flow reactor. Using an RF generator of frequency 13.56 MHz and SiH 4 (5% SiH 4 in N 2) + NH 3 and N 2 as reactive gases and the carrier gas, respectively, we systematically varied the substrate temperature (240–360°C), the partial pressure of reactive gases (0.35 <P SiH 3 P SiH 4 <1.32, 5% of S iH 4 in N 2) and the RF power (20–160 W), as deposition parameters. The characteristics of the films such as composition, deposition rate, refractive index and hydrogen content were investigated by AES, ellipsometry, FTIR spectrometry, nanospec and spectroscopic ellipsometry. As a result of these measurements, well-known characteristics were observed as a function of the substrate temperature and the partial pressure of the reactive gases. However, in our investigation of the RF power dependence of the refractive index of the film, we found that the refractive index increases and then decreases as we increase the RF power. To explain this, we considered the RF power-dependent heating effect in the glow discharge process and the amount of NH radicals which increases with the RF power.

ChemInform Abstract: Characterization of Silicon Nitride Films Deposited on GaAs by RF Magnetron Cathodic Sputtering. Effects of Power Density and Total Gas Pressure

Abstracton the film composition, stress, and critical electric field are studied.

Characterization of Silicon Nitride Films Deposited on GaAs by RF Magnetron Cathodic Sputtering: Effects of Power Density and Total Gas Pressure

Deposition of silicon nitride films on by RF magnetron reactive sputtering of an elemental silicon target in a nitrogen/argon 1:1 plasma has been investigated. Deposition parameters, such as power density and total gas pressure, have been studied in relation to film atomic composition, oxygen contamination, stress, and the critical electric field. The refractive index, measured by ellipsometry, has been correlated to the film composition measured by nuclear reaction analysis. AES profiling of the interfaces after annealing (850°C) showed that magnetron sputtered silicon nitride films are suitable for encapsulation. Furthermore, preliminary electrical results of annealed materials showed that, under correct deposition parameters, critical fields as high as are readily attainable.

Characterization of silicon nitride films formed in an RF glow discharge

Silicon nitride (SiN) thin films have been deposited using radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD) methods. The RF sputtering is carried out in a mixture of Ar and N 2 gases with a Si 3N 4 target. In the PECVD method, a mixture of SiH 4 and NH 3 gases is decomposed by a glow discharge (GD). The relations between the deposition parameters and the properties of the SiN films are investigated for both methods. The formed films are characterized by measurements of refractive index, optical band gap and infrared absorption. The results indicate that the refractive index of RF sputtered films changes from that of pure Si to that of Si 3N 4 formed by a thermal decomposition method as the flow rate of N 2 gas increases, while the optical band gap does not expand. On the other hand, the refractive index of PECVD films is nearly constant under various conditions and is less than that of Si 3N 4, and the optical band gap increases with an increase in the flow ratio of NH 3 to SiH 4. Moreover, the infrared absorption spectra show several bonding modes in the films such as Si-N, Si-H, N-H stretching and N-H, N-H 2 bending modes, and the peak intensities change depending on the deposition conditions. It is suggested from the results that the PECVD films correspond to Si(NH) 2 rather than Si 3N 4. The results obtained by Auger electron spectroscopy and Raman spectroscopy are also used for the discussion.

Characteristics of Thermal Silicon Nitride Films Grown in Argon‐Diluted Ammonia

Characteristics of silicon nitride films thermally grown in argon‐diluted ammonia have been studied. Typical film thicknesses were 30–45Å after nitridation for 10 min to 2h at 1150°C. The as‐grown films are oxynitrides with similar oxygen depth profiles irrespective of their different growth conditions. Origin of the observed high surface oxygen content in the films is suggested to be due to oxidation during wafer unloading. As the oxygen content of the film increases, the Si‐N infrared absorption band shifts toward higher wave numbers. Reduction of the interstitially dissolved oxygen in the silicon substrate was detected by infrared spectroscopy after the thermal nitridation cycle. This process is apparently accelerated by the injection of vacancies at the interface during direct nitridation of silicon. Steam oxidation resistance of thermal nitrides was found to be sensitive to the oxidation temperature and the thermal nitride growth conditions.

Infrared Spectroscopic Characterization of Silicon Nitride Films—Optical Dispersion Induced Frequency Shifts

Films of Si3N4 on Si substrates were prepared by both sputtering and low pressure chemical vapor deposition. Infrared transmission measurements of the strong 800–900 cm−1 Si-N absorption show large (up to 50 cm−1) shifts as a function of film thickness in the range ∼0.1 to 1.2 μm. The agreement between experimental spectra and simulated spectra calculated from parallel layer optical theory indicates that these shifts can be attributed primarily to optical dispersion distortion effects. However, there is some discrepancy between experiment and theory at the extreme ends of the thickness range for the sputtered films which suggests small intrinsic structural changes of these films may arise as a function of deposition thickness. These results point out the importance of considering optical effects in the interpretation of thin film spectra.

Characterization of Si-N films prepared by reactive ion beam sputtering

Application of silicon-nitride (Si-N) as a passivant in com-pound semiconductor technology requires a low-temperature deposition process to prevent dissociation of the volatile constituents of the semiconductor. With this in mind, an exploratory study of Si-N films prepared at room temperature using low-energy, reactive ion-beam sputtering has been carried out. The electrical and optical characteristics of the films have been studied, and an annealing step is found necessary to reduce the conductivity of the nitride and im-prove the interfacial properties.

DC Conduction in Si3N4 Films Grown by the Pyrolytic Reaction between Silane and Ammonia

The present paper describes experimental studies of the electrical characteristics of silicon nitride films deposited pyrolytically by the reaction between silane and ammonia. The substrates were n- and p-type silicon of various resistivities and also silicon with a tungsten layer on to which the nitride was deposited. The majority of the samples show symmetric behaviour with bias and therefore indicate bulk-conduction processes involving field-assisted hopping in localized levels (the Poole–Frenkel Conduction). A polarity dependent conduction is also observed which can not be explained on the simple space-charge-limited currents theory. For the tungsten-coated samples, a high power law is seen to be operative in the conduction process.

Characterization of Silicon Nitride Films

Various “silicon nitride” films have been prepared from , N2, , and in an rf‐promoted glow discharge reaction. These films are described primarily through the use of infrared absorption. Aided by ultraviolet absorption, the inclusion of excess silicon or of oxygen in the films is readily followed. Changes in index of refraction, etch rates in HF acid, and electrical conductivity of the films are correlated with the optical absorption study. Comparisons of these films with those formed by pyrolysis or by reactive sputtering are made. Some reproducible physical properties of an amorphous film are stated.

Electrical Characteristics of Silicon Nitride Films Prepared by Silane‐Ammonia Reaction

The d‐c conduction and complex dielectric constant of silicon nitride films prepared by silane‐ammonia reaction have been studied as a function of the composition of the gaseous ambient in which they were formed. The d‐c conductivity of the material increases sharply when the silane‐ammonia ratio increases above 0.1. The increased conductivity is characterized by a lowering of the activation energy to about 1.0 ev from 1.5 ev for high resistivity nitride. The current‐voltage characteristics display a In dependence at high fields in the temperature range 200°–500°K. Measurement of the magnitude of the slope of this characteristic and its dependence on film thickness, index of refraction, temperature, and bias polarity suggests that conduction arises from field aided thermal ionization of trapping centers in the bulk of the film, the Poole‐Frenkel effect. It is noted that the magnitudes of the slopes of the experimental In plots, which are twice as large as Schottky emission slopes, are derivable within the framework of the Poole‐Frenkel mechanism only under a special assumption regarding the statistics governing the occupancy of the traps.The relative dielectric constant, , of the films has a constant value of approximately 7 for silane‐ammonia ratios below 0.1 and increases gradually to about 10 for a silane‐ammonia ratio of unity. Very small variations in with frequency and temperature were noted in the range of the measurements, and 200°–500°K. Values of dielectric loss, , lower than 10−3 have been observed for the low silane‐ammonia ratio films, but these are also dependent on substrate surface preparation. An observed dependence of on sample area in some cases suggests the presence of localized film defects in the less carefully prepared samples. No structure in the loss‐frequency‐temperature characteristics of the material has been observed in the above‐mentioned ranges of temperature and frequency that cannot be related to the d‐c conductance of the silicon nitride or to the substrate resistance.