Ammonia Annealing Research Articles

Surface Conditioning of a Cold-Rolled Dual-Phase Steel by Annealing in Nitriding Atmospheres Prior to Hot-Dip Galvanizing

The development of steel grades for automotive applications in the recent years has been driven on by two trends: lightweight and improved crash safety. By using steels like DP (dual phase) the goals of passenger safety, fuel efficiency and environmental friendliness can be met at reasonable price. The favorite corrosion protection method for sheet steels in the car industry is the hot-dip galvanizing process. Here, an approach was made to reduce the surface enrichment of critical alloying elements of a dual phase steel grade by reactive annealing in ammonia containing atmospheres. The effects of this treatment on mechanical properties and hot-dip coating behavior are reported.

Interfacial properties of ZrO2 on silicon

The interface of zirconium oxide thin films on silicon is analyzed in detail for their potential applications in the microelectronics. The formation of an interfacial layer of ZrSixOy with graded Zr concentration is observed by the x-ray photoelectron spectroscopy and secondary ion mass spectrometry analysis. The as-deposited ZrO2/ZrSixOy/Si sample is thermally stable up to 880 °C, but is less stable compared to the ZrO2/SiO2/Si samples. Post-deposition annealing in oxygen or ammonia improved the thermal stability of as-deposited ZrO2/ZrSixOy/Si to 925 °C, likely due to the oxidation/nitridation of the interface. The as-deposited film had an equivalent oxide thickness of ∼1.3 nm with a dielectric constant of ∼21 and a leakage current of 3.2×10−3 A/cm2 at −1.5 V. Upon oxygen or ammonia annealing, the formation of SiOx and SiHxNyOz at the interface reduced the overall dielectric constants.

Gallium nitride surface preparation optimised using in situ scanning tunnelling microscopy

Effective preparation of clean GaN surfaces is vital for surface studies, and also has a key role to play in the development of nitride-based electronic devices, due to the importance of forming good metal–semiconductor contacts. We identify the effect of two common surface cleaning treatments (annealing in ammonia, and sputtering in nitrogen followed by in vacuo annealing) on surface reconstruction, morphology and stoichiometry, by employing a combination of in situ RHEED and scanning tunnelling microscopy (STM), and ex situ X-ray photoelectron spectroscopy (XPS). We show how the defect densities in as-treated GaN surfaces may be reduced by growing thin layers of GaN by low-pressure MBE, a technique compatible with most experimental surface science systems. By using a combination of in situ etching and low-pressure growth, we show that it is possible to obtain very similar surface structures to those obtained by full-scale MBE.

Dielectric property and thermal stability of HfO2 on silicon

A stoichiometric, uniform, and amorphous hafnium oxide thin film is deposited by an atomic layer deposition process. The as-deposited hafnium oxide films showed superior electrical properties compared to zirconium oxides, including a dielectric constant of 23, a flatband voltage shift of +0.3 V, a hysteresis of 25 mV, an interfacial trap density of 1.8×1011 cm−2 eV−1, and a leakage current density several orders of magnitude lower than SiO2 at an equivalent oxide thickness of 9.3 Å, suitable for metal–oxide–semiconductor device applications. The thermal stability of hafnium oxide on silicon was determined to be better than that of zirconium oxide. Post-deposition annealing in oxygen and ammonia further improved the thermal stability of HfO2 to 1000 and 1100 °C, respectively.

Nitriding of iron boride to hexagonal boron nitride

A process for preparing hexagonal boron nitride (h-BN) from iron boride (FeB) has been described for the first time. FeB powder was nitrided in ammonia at 700 K for 24 hours yielding non-crystalline BN and ζ-Fe2N. Subsequent annealing in ammonia for 1 hour at 1273 K resulted in a mixture of crystalline h-BN together with α-Fe, e-Fe3N and γ′-Fe4N. The morphology of the product grains is described. This comprises an iron nitride core loosely encapsulated in a foliated BN layer. The open nature of the product layer may account for the relatively low temperature (700 K) required for the nitriding reaction. These iron containing phases were removed with dilute mineral acid leaving h-BN and trace amounts of FeB49.

Electrical Characteristics of TaOxNy for High-k MOS Gate Dielectric Applications

ABSTRACTIn this paper, we report a process for the preparation of high quality amorphous tantalum oxynitride (TaOxNy) via ammonia annealing of Ta2O5 followed by wet reoxidation for use in gate dielectric applications. Compared with tantalum oxide(Ta2O5), a significant improvement in the dielectric constant was obtained by the ammonia treatment followed by light reoxidation in a wet ambient. We confirmed nitrogen incorporation in the tantalum oxynitride (TaOxNy) by Auger Electron Spectroscopy. By optimizing the nitridation and reoxidation process, we obtained an equivalent oxide thickness of less than 1.6nm and a leakage current of less than 10mA/cm2 at -1.5V. Compared with NH3 nitridation, nitridation of Ta2O5 in ND3 improve charge trapping and charge-to-breakdown characteristics of tantalum oxynitride.

Extrinsic dislocation loop behavior in silicon with a thermally grown silicon nitride film

The effect of a thermally grown silicon nitride (SiNx) film on end-of-range extrinsic dislocation loops in a silicon substrate was investigated by transmission electron microscopy. A layer of extrinsic dislocation loops was formed by annealing a Si wafer amorphized by a Ge+ ion implant. A nitride film was grown on the Si by further annealing in ammonia (NH3) at 810 and 910 °C for 30–180 min. Wafers with a loop layer were also annealed in argon (Ar) at the same conditions as the NH3-annealed wafers to determine loop behavior in an inert environment. Samples annealed in NH3 had a significant decrease in the net number of interstitials bound by the loops, while those annealed in Ar showed no change. The results are explained by a supersaturation of vacancies caused by the presence of the nitride film, resulting in loop dissolution. By integrating the measured vacancy flux over the distance from the nitride/Si interface to the loop layer, we extract an estimate for the relative supersaturation of vacancies at 910 °C, CV/CV*∼4, where CV is the concentration of vacancies and the asterisk denotes equilibrium. We rule out interstitial undersaturation-induced loop dissolution based on loop stability with temperature and oxidation-enhanced loop growth calculations. A comparison with estimated CV/CV* values from a previous report using the same processing equipment and parameters but monitoring the change in Sb diffusivity with nitridation shows excellent agreement.

Effect of rapid thermal annealing on the electrical and physical properties of metalorganic chemical-vapor-deposited TiN

This work reports on the effect of postdeposition thermal treatment using rapid thermal annealing on the physical and electrical properties of metalorganic chemical-vapor-deposited (MOCVD) titanium nitride (TiN) thin films. When ammonia is used as the annealing ambient, the resistivity decreases with increasing annealing temperature. The resistivity of MOCVD TiN was reduced from 6000 to 320 μΩ cm after 800 °C rapid thermal annealing in ammonia (RTN). Annealing in nitrogen ambient was found to be not nearly as effective as that in ammonia. The decrease in resistivity may be attributed to a reduction in the carbon and oxygen content, growth in grain size through polycrystalline recrystallization, as well as to an increase in film density.

Titanium nitride films for barrier applications produced by rapid thermal CVD and subsequent in-situ annealing

TIN films with a thickness of typically 50 nm were deposited by rapid thermal chemical vapour deposition (RTCVD) using a TiCl 4 NH 3 process. The deposition temperature was varied between 300 °C and 600 °C. The aim was to develop a low-temperature CVD process with low film contamination for diffusion barriers. We achieved this by an in-situ annealing step immediately after deposition. A step coverage of nearly 100% and an excellent yield concerning barrier failures could be reached. The composition of the films was characterized by Rutherford backscattering spectroscopy, the structure by X-ray diffraction. The chlorine and oxygen contents highly depend on the chemical reactivity of the annealing gas. Deposition at 450 °C and subsequent annealing in ammonia at 450 °C leads to a very low chlorine content (<1.5 at.%) and a low specific resistivity of 250 μΩ cm. Apparently the chlorine can be mobilized during annealing and desorbed effectively from the surface by using an appropriate annealing gas. The chlorine uptake and loss can be traced by the lattice parameter as an indicator. At deposition temperatures higher than 350 °C, the films show a columnar growth with a 〈100〉 texture. Below 350 °C, chlorine-rich fine-grained polycrystalline TiN is deposited and can be purified by annealing. The crystallinity is not changed essentially by the anneal step. Its main action is to remove defects remaining after low-temperature deposition. With its low fabrication temperature and good film properties, this process can be used for barrier applications in multilayer metallization.

The hydridation and nitridation of GeSi oxide annealed in ammonia

A 110-nm-thick Ge0.38Si0.62O2 film on Ge0.38Si0.62 was annealed in NH3 at 700 °C for 4 h and analyzed by Auger electron spectroscopy, backscattering spectrometry, x-ray photoelectron spectroscopy, and secondary-ion mass spectrometry. In the surface region of the oxide film, this annealing results in an incorporation of nitrogen bonded to germanium by the nitridation of GeO2. In the bottom region of the oxide film near the GeSi/oxide interface, elemental Ge appears. We attribute this process to the hydridation of GeO2 with hydrogen that comes from dissociated ammonia. Results obtained at 800 °C for a 380-nm-thick oxide film are similar. A model is proposed to explain the observed changes of the oxide after the ammonia annealing.

Chemical Surface Modification of Porous Silicon

Resistance to room temperature oxidation and control over wetting properties can be achieved by chemical modification of a porous‐silicon surface. Fourier transform infrared spectroscopy was used in the transmission mode to monitor the surface chemistry of both treated and untreated porous‐silicon samples before and after exposure to humid air at room temperature. Surface modification methods investigated include: (i) vapor‐phase silation using either hexamethyl‐disilazane or trimethylchlorosilane, and (ii) rapid thermal annealing in nitrogen, ammonia, or argon ambients. The silation treatments, carried out in the presence of trace moisture, were successful both in creating surface trimethylsilyl groups and in suppressing room temperature oxidation. Rapid thermal annealing at temperatures as low as 500°C for 30 s eliminates all silicon hydrides. Nitrided porous‐silicon layers are formed at 1100°C in either ammonia or nitrogen; in both cases the silicon nitride infrared absorption peaks scale with the porous layer thickness, indicating that the compounds are distributed throughout the porous layer.

Phase transition in B1-type Mo 1− xNb xN sputtered films under ammonia annealing

B1-type solid solution Mo 1− x Nb x N sputtered films were annealed at 500–900°C for 5–100 hr under flowing ammonia, in order to investigate the stability of B1 structure and phase transition in the solid solution as a function of annealing temperature and chemical composition x. The B1 phase of the MoN films ( x = 0) transferred to a hexagonal phase above 600°C. In the Mo-rich solid solution films with x ≦ 0.23, the B1 phase was converted to the γ-Mo 2N-type phase between 600°C and 800°C, and the transition temperature increased with increases in x. A hexagonal solid solution with WC-structure was formed in the films with x ≦ 0.38 at 900°C. No phase transition occurred until 900°C in the Nb-rich solid solution films with x ≧ 0.59. The result indicates that the stability of B1 structure in the solid solution was increased by the addition of NbN.

Charge-trapping properties of ultrathin nitrided oxides prepared by rapid thermal annealing

Ultrathin (8 nm) oxides were nitrided by lamp-heated rapid thermal annealing in ammonia at 900-1150 degrees C for 5-300 s. Measurements indicate that both the nitrogen concentration near the Si-SiO/sub 2/ interface (N)/sub int/ and the hydrogen concentration in nitrided oxides (H) increase monotonically as nitridation proceeds. The flat-band voltage shift Delta V/sub VB/ and the increase of the midgap interface state density Delta D induced by the constant-current stress were investigated. While Delta V/sub FB/ increases monotonically as nitridation proceeds, Delta D is found for the first time to show a turnaround with nitridation time: it increases, reaches a maximum at a certain nitridation time, and then decreases gradually to a value that is lower, in some cases, by more than one order of magnitude than that of a thermal oxide. It is found for the first time that Delta V/sub FB/ increases in proportion to (H). Based on the turnaround behavior of Delta D, a two-factor model is proposed in which one factor, (H), increases delta D and the other one, (N)/sub int/, reduces it.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electrical and physical characteristics of thin nitrided oxides prepared by rapid thermal nitridation

Ultrathin oxides (5-12 nm) were nitrided by lamp-heated rapid thermal annealing in ammonia at temperatures of 900-1150°C for 5-300 s. Elemental depth profiles were measured by Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS). Both the nitrogen concentration measured by AES and the hydrogen one measured by SIMS for a nitrided oxide are found to increase monotonically as nitridation proceeds. The AES depth profiles of oxygen show that the Si-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> interface does not move during nitridation. Dependences of midgap interface state density ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D_{it}_{m}</tex> ) and fixed charge density (N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</inf> ) on nitridation temperature and on oxide thickness were studied. For a given temperature, both <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D_{it}_{m}</tex> and (N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</inf> ) are found to show turnarounds as nitridation time increases in a similar manner: at first both increase, reach respective maxima at a certain nitridation time <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t_{\max}</tex> , and then decrease gradually. The ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D_{it}_{m}</tex> ) and (N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</inf> ) increase more rapidly and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t_{\max}</tex> is shorter as the nitridation temperature is raised or the oxide film is thinner. The maximum of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D_{it}_{m}</tex> increases as the oxide film is thinner. A two-step model is newly proposed to explain the turn-around behaviors of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D_{it}_{m}</tex> and N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</inf> : the first step is defect formation as a result of nitrogen incorporation and the second step is reduction of the defects by an annealing-type process. The simulation reproduces the turnaround behaviors very well.

Formation and Passivation of New Paramagnetic Defects Associated With Thermal Oxides On Silicon

AbstractA new spin resonance spectrum has been observed with electron paramagnetic resonance in thermal oxides grown on (111) silicon. Our analysis indicates that this new spectrum consists of two isotropic resonances. One resonance has a g-value of 2.0026 and a linewidth (FWHM) of 1.2 G (labeled SL8); the other resonance has a g-value of 2.0029 and a linewidth (FWHM) of 5 G (labeled SL9). These spectra might be due to impurity contamination resulting from the oxidation process and associated with defects at interior surfaces. The SL8 resonance in particular appears to be located within the as-grown thermal oxide. The effects of 60Co gamma irradiation and annealing in either hydrogen or ammonia on these spectra are also presented in this paper.

Preparation and characterization of fcc MoxNb1−x(NyC1−y)z thin films

In an attempt to make the predicted high superconducting transition temperature (Tc) form of MoN, we have prepared and characterized thin films of MoxNb1−x(NyC1−y)z, where 0.93&amp;gt;x&amp;gt;0, 1.0&amp;gt;y&amp;gt;0.8, and 1.0&amp;gt;z&amp;gt;5. These films were reactively rf sputtered in a UHV system using an evenly split Nb–Mo split target and mixtures of argon, nitrogen, and cyanogen gases. Films prepared at elevated substrate temperatures (600–800 °C) were all of single phase NaCl (or Bl) structure with varying amounts of nitrogen deficiencies. Both the lattice parameter and Tc were found to be smoothly varying functions of composition and to correlate with deviations from stoichiometry of the molybdenum-rich samples. Ion implantation of nitrogen into several of the more nitrogen deficient films resulted in both the lattice parameter and the Tc moving toward the values expected for stoichiometric films of the same Mo content. Results of postdeposition plasma nitriding and thermal ammonia annealing are also discussed.

Radiation effects in nitrided oxides

Electron radiation effects on silicon dioxide films, before and after ammonia annealing (nitridation), have been studied. The most striking result is that the generation of radiation-induced interface states is nearly eliminated in the nitrided oxides.