Compositional analysis of silicon oxide/silicon nitride thin films (original) (raw)
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Spectroscopy Letters, 2017
The effect of thermal annealing on the optical and physico-chemical properties of hydrogenated silicon nitride films was studied. These films were deposited by plasmaenhanced chemical vapor deposition from a mixture of silane, ammonia and nitrogen. Subsequently, the films were annealed at various temperatures ranging from 400 to 1000 degrees Celsius. The properties of the films were studied using ellipsometry and Fourier transform infrared spectroscopy. The Maxwell Garnet model considers the silicon nitride material as heterogeneous with three distinct phases: silicon, stoichiometric silicon nitride and hydrogen. Based on the ellipsometric analysis, the annealing treatment leads to reduce the volume fraction of both hydrogen and silicon. As a result, the stoichiometry parameter significantly increases from 1.24 to 1.32 making it closer to the stoichiometric silicon nitride one. According to the infrared data, a noticeable decrease in the total hydrogen concentration in the films was obtained with respect to the annealing temperature.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1997
The chemical composition of ultrathin oxide-nitride-oxide multilayer films grown onto p-type silicon substrates and subjected to different annealing processes and to various oxidation times of the nitride layer has been studied by means of x-ray photoelectron spectroscopy and time-of-flightsecondary-ion-mass spectroscopy. Our results show that the annealing process strongly influences the bottom SiO 2 /Si interface allowing the saturation of the dangling bonds present at this interface and decreasing the concentration of free hydrogen. By increasing the oxidation time, a better silicon dioxide layer is formed in the topmost layer of this structure.
2001
The deposition of amorphous hydrogenated silicon oxynitride thin ®lms, varying the nitrogen and oxygen content in the solid phase, is reported. The ®lms were deposited by plasma enhanced chemical vapor deposition at dierent nitrous oxide/silane¯ow ratios, keeping constant the silane¯ow and the deposition temperature at 320°C. The composition of the thin ®lms was determined by Rutherford backscattering spectroscopy (RBS) and the morphological properties were investigated by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The composition data showed that the oxygen content increases and the nitrogen content decreases, inside the ®lms, as the ratio between the nitrous oxide¯ow and silane¯ow goes toward larger values. The oxygen (x) plus nitrogen (y) content in the chemical formula (a-SiO x N y is always close to two, suggesting that these atoms share the same atomic positions around the silicon atoms in a local structure similar to SiO 2. The SAXS results revealed the presence of scatterers with an average radius hRi that varies from small values, like 10 A, up to 100 A. The TEM results showed the formation of particles with a circular cross-section, composed of Si, N and O spread in a matrix with the same elemental composition. These particles have a radius larger than 50 A.
Structural investigation of Si-rich amorphous silicon oxynitride films
Thin Solid Films, 2003
In this work we investigated the structural and chemical properties of amorphous silicon oxynitride thin films, with distinct composition, deposited by plasma enhanced chemical vapor deposition from nitrous oxide and silane gas precursors. The utilized characterization techniques were Rutherford backscattering spectroscopy, X-ray absorption spectroscopy at the Si K-edge, and Fourier transform infrared spectroscopy. The results show a silicon first coordination shell composed of silicon, oxygen and nitrogen atoms, in a proportion that fits their atomic content. The Si-Si bonds are found only in samples having silicon content higher than ;50 at.%. These films also present higher amount of Si-H bonds. The film having the highest Si content, which shows evidences of Si clustering, was annealed in vacuum at 550, 750 and 1000 8C. The results demonstrated that the annealed film is chemically stable under heat treatments in vacuum up to 1000 8C. The hydrogen is totally released at 750 8C. The main effect of the annealing process is to increase the segregation of silicon clusters.
Determination of silicon nitride film chemical composition to study hydrogen desorption mechanisms
Thin Solid Films, 2011
To go further in the comprehension of hydrogen desorption mechanisms from PECVD (Plasma Enhanced Chemical Vapour Deposited) silicon nitride, a method to determine the chemical composition of amorphous silicon nitride films using fast and non destructive characterization techniques has been developed. In particular, Si\H, N\H, Si\Si and Si\N bond concentrations are calculated from Fourier transform infra red spectroscopy, ellipsometry and mass measurement. Next, different PECVD silicon nitride films were annealed at 600°C during 2 min. Results show that hydrogen desorption from PECVD silicon nitride depends on film mass density and main chemical reactions leading to hydrogen desorption are identified thanks to the determination of Si\Si and Si\N bond concentrations.
The effect of thermal annealing on the properties of PECVD hydrogenated silicon nitride
physica status solidi (c), 2012
Silicon nitride (SiN x) thin films were grown on silicon by plasma-enhanced chemical vapor deposition (PECVD) method at low temperature by varying the silane (SiH 4) to nitrogen (N 2) ratio in the plasma. As-deposited samples were investigated by varying annealing temperature from 400 °C to 950 °C in infrared (IR) heated belt furnace, in order to study their properties and correlate them to the chemical composition of the layers to find the optimized condition for application in silicon solar cells.
Experimental and theoretical studies on N 1s levels of silicon oxynitride films
Surface Science, 2002
Nitridation of silicon dioxide layers at low temperatures by the use of nitrogen plasma generated by low energy electron impact has been investigated by means of X-ray photoelectron spectroscopy. The nitrogen concentration is increased by the application of a negative bias voltage to the specimen, indicating that N þ ions are the reacting species. When nitridation is performed above 450°C, only one peak is observed at 397.9 eV, and it is attributed to N(-Si) 3 (nitrogen atom bound to three Si atoms). For the nitridation below 400°C, on the other hand, a peak appears at 399.2 eV in addition to the 397.9 eV-peak. When the film nitrided at 400°C is heated at 700°C in a vacuum, the intensity of the 399.2 eV-peak is slightly decreased, and new peaks appear at 399.9, 400.7 and 402.4 eV. The 399.9, 400.7, and 402.4 eV-species are not formed when the nitrided oxide layers containing no 399.2 eV-species are heated at 700°C, showing that these species are produced from the 399.2 eV-species. Theoretical calculations using a density functional theory method show that O-N(-Si) 2 (nitrogen atom bound to two Si atoms and one oxygen atom) has an N 1s level shifted by þ1.3 eV from that of N(-Si) 3 , indicating that the 399.2 eV-peak is attributable to O-N(-Si) 2 . This species is likely to be easily formed by the insertion of N þ ions to the SiO 2 surface without an extensive atomic rearrangement. The calculations also show that O-N Å -Si (nitrogen radical bound to both one oxygen and Si atoms) and O@N-Si (nitrogen atom with an N@O double bond and an Si-N single bond) have þ1.8 and þ3.1 eV energy shifts, respectively, from the N 1s peak of the N(-Si) 3 species, leading to the attribution of the 399.9 eV-peak to O-N Å -Si and the 400.7 eV-peak to O@N-Si. The calculations also show that the 402.4 eV-peak is attributable to [N(-Si) 4 ] þ (a cation composed by a nitrogen atom bound to four Si atoms). The concentrations of the [N(-Si) 4 ] þ and O@N-Si species are almost constant throughout the nitrided oxide layers, showing that these species result from the reaction between O-N(-Si) 2 and bulk SiO 2 . The concentration of O-N Å -Si species, on the other hand, is low at the surface and high near the interface, showing that O-N Å -Si is formed by the reaction with Si.
Microelectronics Reliability, 2006
This work reports a detailed study of the re-oxidation effects on the hydrogen content and optical properties of silicon oxynitride films grown by plasma enhanced chemical vapor deposition (PECVD) with N 2 O, NH 3 and SiH 4 as the precursors. Results showed that the silicon oxynitride deposited with gas flow rates of NH 3 /N 2 O/SiH 4 = 20/500/20 (sccm) has favorable properties for integrated waveguide applications. The refractive index of this layer is about 1.57 at 632.8 nm wavelength and the layer has a comparative low density of NAH bonds. With a high temperature re-oxidation of the as-deposited film, the hydrogen content of the oxynitride film was reduced from 2.255 · 10 22 to 6.98 · 10 20 cm À3 which is attributed to the removal of excess silicon oxidation and hydrogen bonds.
Characterization of silicon nitride thin films deposited by hot-wire CVD at low gas flow rates
We examined the chemical, structural, mechanical and optical properties of amorphous hydrogenated silicon nitride thin films deposited by hot-wire chemical vapour deposition using SiH 4 , NH 3 and H 2 gases at total flow rates below 33 sccm. Time of flight secondary ion mass spectroscopy reveal that the film surfaces consist of predominantly Si with hydrogenated Si x N y O z species. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy corroborate on the N/Si ratio. Electron energy loss spectroscopy discloses that the thickness of the nitrogen rich oxidized interface between the SiN x films and the c-Si substrate decrease with an enhancing NH 3 flow rate. By varying the NH 3 flow rate, dense SiN x films can be realized with hydrogen content between 16 and 9 at.%, a refractive index between 3.5 and 1.9 and optical band gap ranging from 2 to 4.5 eV. The SiN x film stress is compressive for N/Si < 0.4 and tensile for higher N/Si > 0.55. Mechanisms relating the HWCVD conditions and the film structure and properties are proposed.