Properties Of Silicon Nitride Films Research Articles

Dielectric properties of silicon nitride films deposited by microwave electron cyclotron resonance plasma chemical vapor deposition at low temperature

The dielectric properties of amorphous silicon nitride (SiNx) films that were prepared by microwave electron cyclotron resonance plasma chemical vapor deposition at low temperature in the frequency range 5 Hz–1 MHz have been investigated. The dielectric dispersion in the frequency range exhibits two fractional power laws of (ε′−ε∞′)∝ω−p1 and (ε′−ε∞′)∝ωn1−1 with p1=0.12–0.18 and n1=0.95–0.96. These are close to the result predicted by the many-cluster anomalous conduction theory of fractal structure.

Gate dielectric properties of silicon nitride films formed by jet vapor deposition

High-quality silicon nitride (or oxynitride) films made by a novel jet vapor deposition (JVD) technique are described. The JVD process utilizes a high-speed jet of light carrier gas to transport the depositing species onto the substrate to form the desired films. The film composition has been determined to consist primarily of Si and N, with some amounts of O and H. MNS capacitors based on the JVD nitride films deposited directly on Si exhibit relatively low densities of interface traps, fixed charge, and bulk traps. The interface traps at the nitride/Si interface exhibit different properties from those at the SiO 2/Si interface in several aspects. In contrast to the conventional CVD silicon nitride, the high-field I-V characteristics of the JVD silicon nitride fit the Fowler-Nordheim tunneling theory over 4–5 orders of magnitude in current, but do not fit at all the Frenkel-Poole transport theory. This is consistent with the much lower concentration of electronic traps in the JVD silicon nitride. Results from the carrier separation experiment indicate that electron current dominates the gate current with very little hole contribution. Both theoretical calculation and experimental data indicate that the gate leakage current in JVD silicon nitride is significantly lower than that in silicon dioxide of the same equivalent oxide thickness. Compared to their MOSFET counterparts, MNS transistors exhibit reduced low-field transconductance but enhanced high-field transconductance, perhaps due to the presence of border traps.

The investigation of properties of silicon nitride films obtained by RPECVD from hexamethyldisilazane

The silicon nitride films were obtained by remote plasma enhance chemical vapor deposition (RPECVD) using hexamethyldisilazane or its mixture with ammonia in the range 373–773 K. The correlations between the chemical composition, deposition rates, optical, electrical and structural properties and the growth conditions were established. It was found that the formation of two polycrystalline hexagonal phases SiC and Si 3N 4 was realized by using pure hexamethyldisilazane as precursor. The ammonia addition in gas mixture leaded to change of the chemical composition and structure of silicon nitride films, namely, the disappearance of carbon-bonding and SiC formation, and the order of hexagonal silicon nitride.

Nitrogen plasma instabilities and the growth of silicon nitride by electron cyclotron resonance microwave plasma chemical vapor deposition

Nitrogen plasma instabilities have been identified through fluctuations in the ion current density and substrate floating potential. The behavior of the plasma instabilities was found to be confined to the pressure regime 0.9 mTorr<P<1.6 mTorr. The onset of instabilities in the nitrogen plasmas occurred following the transition from an underdense to overdense plasma, where an overdense plasma is defined for densities greater than the critical density nc=7.4×1010 cm−3. The instabilities are a consequence of the nonlinear dynamics present in electron cyclotron resonance (ECR) plasmas and indicative of a transition between plasma modes as the pressure increases from 0.9 to 1.6 mTorr. The plasma instabilities are suppressed with the introduction of silane for the deposition of silicon nitride, although the plasma still undergoes a transition from an underdense to overdense plasma at 1.0 mTorr. The transition pressure delineated regions of poor and optimum electrical properties of silicon nitride films deposited from a dilute nitrogen-silane (N2/SiH4=5) plasma. To evaluate growth conditions, the flux of energetic ions to deposited atoms was approximated by examination of the ratio of ion current density to deposition rate. This ratio was found to be well correlated to the electrical properties of ECR microwave plasma deposited silicon nitride films for pressures above the underdense to overdense transition at 1.0 mTorr.

Electrical properties of silicon nitride films grown on a SiGe layer by distributed electron cyclotron resonance plasma-enhanced chemical vapor deposition

Silicon nitride films have been deposited on relaxed Si 0.83Ge 0.17 films using distributed electron resonance plasma-enhanced chemical vapor deposition without intentional substrate heating. The electrical properties of metal–insulator–semiconductor structures have been investigated. The electrical properties are strong functions of the post-processing treatment. The hysteresis of C–V curves can be reduced significantly after 30 min post-metallization annealing at 450 °C in forming gas. The flat-band voltage is then very low, thereby indicating that positive charges retained in the silicon nitride films are compensated for by negative charges located at the interface with the SiGe alloy. Conduction properties have also been analyzed from I–V measurements. A critical field of ≈2 MV cm −1 and a high resistivity of ≈2×10 15 Ω cm have been obtained. For higher electric fields, the leakage current is governed by a Poole–Frenkel conduction mechanism.

Gate quality Si3N4 prepared by low temperature remote plasma enhanced chemical vapor deposition for III–V semiconductor-based metal–insulator–semiconductor devices

We report the properties of silicon nitride films deposited by the electron cyclotron resonance remote plasma enhanced chemical vapor deposition method on Si substrates using SiH4 and N2. The effects of nitrogen/silane gas ratio (R=N2/SiH4), electron cyclotron resonance power, substrate temperature, and H on growth, refractive index, chemical composition, and etch rate were investigated. Nominally stoichiometric Si3N4 films were obtained with a refractive index of 1.9∼2.0 at a wavelength of 632.8 nm. The etch rate of the films in a buffered HF solution (7:1) was low (∼0.7 nm/min) and increased with increasing H2 gas flow rate and decreasing substrate temperature during deposition. Fourier transform infrared spectroscopy and high temperature thermal evolution experiments showed very small amounts of H in the films. A leakage current less than 100 pA/cm2 at a field of 2 MV/cm, a resistivity of ≳4×1017 Ω cm, and breakdown strengths of 6–11 MV/cm at a current density of 1 μA/cm2 were observed. These properties are comparable to those of Si3N4 prepared by conventional high temperature (700 °C) chemical vapor deposition. The performance of GaAs-based field-effect-transistors in switching and power applications can be enhanced substantially by employing a metal-insulator-semiconductor structure. By taking advantage of an in situ process approach, insulator-GaAs structures were successfully gated with excellent interfacial properties.

Synthesis and corrosion properties of silicon nitride films by ion beam assisted deposition

Silicon nitride films SiN x were deposited on 316L austenitic stainless steel substrates by silicon evaporation and simultaneous nitrogen ion irradiation with an acceleration voltage of 2 kV. In order to study the influence of the nitrogen content on changes in stoichiometry, structure, morphology, thermal oxidation behaviour and corrosion behaviour, the atom to ion transport ratio was systematically varied. The changes of binding states and the stoichiometry were evaluated with XPS and AES analysis. A maximum nitrogen content was reached with a Si N transport ratio lower than 2. The films are chemically inert when exposed to laboratory atmosphere up to a temperature of more than 1000°C. XRD and SEM measurements show amorphous and featureless films for transport ratios Si N from 1 up to 10. The variation of the corrosion behaviour of coated stainless steel substrates in sulphuric acid and hydrochloric acid shows a minimum at medium transport ratios. This goes parallel with changes in porosity and adhesion. Additional investigations showed that titanium implantation as an intermediate step improves the corrosion resistance considerably.

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.

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

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

Optical properties of silicon nitride films deposited by hot filament chemical vapor deposition

Silicon nitride films were deposited at low temperatures (245–370 °C) and high deposition rates (500–1700 Å/min) by hot filament assisted chemical vapor deposition (HFCVD). Optical properties of these amorphous silicon nitride thin films have been extensively characterized by absorption, photoluminescence (PL), photoluminescence excitation, and electroluminescence measurements. The optical band gap of the films was varied between 2.43 and 4.74 eV by adjusting the flow rate of the disilane source gas. Three broad peaks at 1.8, 2.4, and 3.0 eV were observed in the PL spectra from these films. A simple qualitative model based on nitrogen and silicon dangling bonds adequately explains the observed PL features. The photoluminescence intensity observed in these films was 8–10 times stronger than films deposited by plasma enhanced chemical vapor deposition, under similar conditions. The high deposition rates obtained by HFCVD is believed to introduce a large number of these optically active defects.

Properties of silicon nitride films prepared by magnetron sputtering

Numerous silicon nitride films were prepared using different target materials (Si3N4 or Si) and different discharge gases (Ar or N2). In the case with an Si4N4 target and Ar gas pressure (1 Pa), the N-to-Si atomic ratio of the film was stoichiometric, 1.33, even when the substrate temperature was changed considerably. When the As gas pressure was increased from 1 7 Pa, the nitrogen content increased while the deposition rate decreased. In the case with an Si3N4 or Si target and N2 gas, the nitrogen content increased while the deposition rate decreased with the increase in N2 pressure. The change in deposition rate due to the pressure was investigated using optical emission spectroscopy.X-ray photoelectron spectroscopy analysis showed that the binding energy is the same if the N-to-Si ratio was in the range from 1.33 to 1.70. It was found by X-ray diffraction analysis that crystallization occured when the substrate temperature was higher than about 1173 K.

Vibrational property of the slow N 2 + ions deposited SiNx films

We have investigated vibrational properties of silicon-nitride films, SiNx (0.3≤×≤1.33), produced by a non-thermal method using high-resolution electron energy loss spectroscopy. The results, based on a continuous random network model assuming a planar XY3 vibrational bond unit, show that the Si-N bonds in the films closely resemble those in typical thermal silicon nitride although nitrogens occupy some metastable binding sites. We estimate force constants of the restoring forces for a Si3N bond unit, which tend to increase gradually with increasing nitrogen content x. In particular, the central force constant k1 for the in-plane stretching mode of silicon atoms varies with x in the range 297≤k≤331 N/M, larger than the theoretical value for a nitrogen atom imbedded in a pure Si crystal.

Total Pressure Effects on the Properties of Silicon Nitride Films Fabricated by Photoenhanced Chemical Vapor Deposition

Silicon nitride ( SiNx ) films were deposited on (100)Si substrates using silane and ammonia gases by the direct-photolysis photoenhanced chemical vapor deposition method at 280° C. The depositions were performed with emphasis on the total pressures, which ranged from 0.51 Torr to 4.04 Torr. As the total pressure increased, the film resistivity decreased from 3.7×1015 Ω· cm to 4.8×109 Ω· cm. The effective trapped carrier density at the SiNx /(100)Si interface reached a minimum value (2.1×1010 cm-2) at 1.52 Torr. The film included silicon bonded with silicon (Si–Si) components as well as nitrified silicon (Si–N) components. The Si–Si components increased and the Si–N components decreased in number as the total pressure increased. Based on these results and gas analysis findings, two important reactions to characterize the film properties were discussed.

Electrical Properties of Silicon Nitride Films Prepared by Photo-Assisted Chemical Vapor Deposition under Controlled Decomposition of Ammonia

Silicon nitride (SiNx) films have been deposited at lower substrate temperatures (≤500°C) by direct (without Hg-sensitization) photo-chemical vapor deposition (photo-CVD) with a low-pressure Hg lamp using SiH4 and NH3. The resistivity was as high as 5×1016 Ωcm. The minimum value of interface-trap density in Al/SiNx/Si metal-nitride-semiconductor (MNS) diodes was estimated to be 9×1010 cm-2 eV-1 by a quasi-static capacitance-voltage measurement. In contrast to conventional plasma CVD of SiNx, the formation of intermediate species is controlled by the decomposition of NH3 which is decomposed to a lesser extent in a plasma process, based on analyses of film structures and transient mass spectroscopy. This effect causes the properties of SiNx to not change in a wide range of NH3/SiH4 gas composition.

Properties and Thermal Behaviour of Si3N4 Thin Films

AbstractThe applications of thin film technologies are increasing. A variety of different ceramic and hard coating materials are deposited. Silicon nitride is one of the materials which seems to be quite interesting for the use as coating material. An use as a wear and corrosion protective coating seems to be conceivable. Silicon nitride is known to have a good thermalshock resistivity, thermal and chemical stability and good mechanical and wear resistant properties. If these properties are also given for deposited metastable PVD Si-N-coatings has to be evaluated yet.This paper describes the influence of different coating process parameters of the MSIP process like DC and RF mode, reactive and non reactive sputter processes and target orientation on the properties of silicon nitride films. It is shown, that coatings deposited with a 100 oriented single crystal target have the highest deposition rate and the best mechanical properties. The thermal stability of these thin films is insufficient although it can be improved by a carbon incorporation.

Effect of substrate bias on properties of silicon nitride films prepared by activated reactive evaporation

Substrate biasing was explored to improve the quality of activated reactive evaporation processed (ARE) silicon nitride films. The samples were prepared at various r.f. (radio frequency) substrate bias power for a given electron beam current, pressure, and r.f. discharge powet. The quality of the ARE silicon nitride deposited at over 150 W of substrate bias was comparable with high temperature processed CVD films. These films showed a refractive index of 2.00, an absorption edge of 4.9 eV, a dielectric constant of 7.2–7.7 and hydrogen and oxygen concentrations far less than 1 at.%.

Characterization of Reactively Sputtered Silicon Nitride

The properties of silicon nitride films, formed by the reactive sputtering of a silicon target using various gas flow ratios, are presented. The variation in physical, optical, and electrical properties of this silicon nitride series is examined. The electrical properties of these films on Si wafers are examined and compared with those of other silicon nitride films. The potential of passivating electronic devices with the films is investigated.

Composition, structure and properties of silicon nitride films grown from dichlorosilane and ammonia at low pressure

The influence of the synthesis temperature on the composition, structure and physico-chemical properties of silicon nitride films, produced from dichlorosilane and ammonia at low pressure is investigated. It is found that films, grown in the temperature range 750–840°C, are amorphous, close to the stoichiometric ones, and are homogeneous in composition and properties. Increasing the deposition temperature results in a decrease of the etching and oxidation rates. These relationships become saturated in the temperature range 800–850°C. The films have good dielectric properties.

Spectroscopic ellipsometric measurements of plasma-enhanced chemical vapour deposition-grown SiN x InP structure

InP has received considerable attention due to its large saturated electron drift velocity and the lower density of surface states at an insulator-Inp interface than at an insulator-GaAs interface. Silicon nitride films, formed by plasma-enhanced chemical vapour deposistion (PECVD), have many applications in compound semiconductor device fabrication and have been used mainly as passivation films for optoelectronic devices based on InP [1]. There have been various investigations into the structural properties of silicon nitride films on an InP substrate, viz. Auger electron spectoscopy (AES) [2], X-ray photoelectron spectroscopy (XPS) [3] and electron-spin resonance (ESR) [4] measurements, etc., but analysis based on the spectroscopic ellipsometer is rare. A spectoscopic ellipsometer is a surface analyser surpassing the limitations of the conventional ellipsometer, which is used in the non-destructive measurement of the thickness and quality of very thin films by using the characteristics of light, the phase of which is very sensitively changed with the existence of very thin films. Thus, its availability has extended to various surface and multilayer analyses [5 -81. In this letter we report spectroscopic ellipsometry measurements of SiNxln p (n-type) grown by PECVD with various NH3:SiH 4 ratios. A PECVD apparatus designed in-house [9] with a hot-wall capacitively coupled-type reactor was used to deposit the silicon nitride film using a diluted silane (5% Sill4 in N2), ammonia (99.999% purity) and nitrogen (99.9999% purity) gas mixture, on n-type wafers with (100) orientation and 1.3 x 1018 cm -3 electron concentration. The wafers were sequentially cleaned by standard organic solutions (trichloroethylene, acetone and methanol), and then rinsed in deionized water. The native oxide on the surface of the wafer was etched in an acid solution ( H 2 S O 4 : H 2 0 2 : H 2 0 = 3:1:1 ) for 60s and subsequently in an HF (49%) solution (HF:H20 = 1:1 ) for another 60 s. After rinsing in deionized water the wafers were blow-dried with nitrogen. For oxygenfree silicon nitride film the reactor was heated at 300 °C and purged with dry N2 gas flow for 1 h before silicon nitride deposition. We varied the NH3/SiH4 gas flow ratios from 0.205 to 0.686 at a substrate temperature of 300 °C, r.f. power of 60 W and total operation pressure of 66.7 Pa. The forma-

Effects of wet oxidation on the electrical properties of sub-10 nm thick silicon nitride films

Capacitors with sub- 10 nm thick oxidized nitride layers formed by wet oxidation of 8 nm thick silicon nitride films deposited on a polysilicon substrate were prepared. The effects of the wet oxidation time on the electrical properties of the silicon nitride film itself have been investigated with oxide/nitride composite film and oxidized nitride film by removing the top oxide from the oxide/nitride composite film. The capacitance of the capacitors consisting of oxide/nitride composite film decreases sharply and their breakdwon fields increase with increasing thickness of the top oxide layer. On the contrary, the capacitance and breakdown fields of silicon nitride layer, which was created by removing the top oxide layers grown thermally on silicon nitride, increase with increasing wet oxidation time. The reduction of thickness and the improved quality of silicon nitride are responsible for the improved capacitance and increased breakdown fields of nitride layer, respectively. In addition, wet oxidation improves the intrinsic TDDB characteristics and the early breakdown failure rate of silicon nitride film itself, probably due to the reduction of defects in the silicon nitride. Consequently, silicon nitride film created by removing top oxide is suitable for dynamic memories as a thin dielectric film.