Titanium nitride films were formed by chemical vapor deposition from titanium tetrabromide and ammonia at atmospheric pressure and substrate temperatures from about 400 to 600 °C. Although titanium tetrabromide is a highly hygroscopic solid at room temperature, it can be handled conveniently as a very concentrated liquid solution (85 weight percent) in bromine as a solvent. This solution can be vaporized by a direct liquid injection system. Alternatively, the solution can be pumped into a bubbler, from which the bromine solvent is then removed by fractional distillation. Rutherford Backscattering Spectroscopy was used to determine that the bromine content of TiN deposited at 500°C was about one atomic per cent. Growth rates were about 17 nm/min, and electrical resistivity was found to be about 200 μΩ-cm.

Depositions of high quality zirconium nitride, (Zr3N4), films using the metal-organic precursor Zr(Net2)4 were carried out in a microwave argon/ammonia plasma (2.45 GHz). The films were deposited on crystalline silicon wafers and quartz substrates at temperatures of 200–400 °C. The transparent yellow films have resistivity values greater than MΩ cm. The stoichiometry is N/Zr = 1.3, with less than 5 atom % carbon and little of no oxygen. The hydrogen content is less than 9 atom %, and it does not vary with deposition temperature. The growth rates range from 600 to 1200 Å/min, depending on the flow rates and precursor bubbler temperature. X-ray diffraction studies show a Zr3N4 film deposited at 400 °C is polycrystalline with some (220) orientation. The crystallite size is approximately 30 Å. The band gap, as estimated from transmission spectra, is 3.1 eV.

Tantalum nitride thin films were produced by nitridation of sol-gel tantala thin films. The oxidation kinetics and the activation energy for oxidation were investigated and compared to those of sputtered tantalum nitride thin films. Data was gathered from in situ sheet resistance measurements taken between 550 and 720 K. Sol-gel films exhibited parabolic oxidation kinetics and had an activation energy of 1.9 eV. Sputtered films displayed quartic oxidation kinetics at lower temperatures tending toward cubic kinetics at higher temperatures and had an activation energy of 1.6 eV.

A study has been conducted on the mechanical, tribological and chemical properties of pulsed laser deposited (PLD) TiC, VC and TiCNC thin films. The TiC films were deposited at 375°C and 5 mTorr Ar, while the TiCNC films were deposited from a composite target at 475°C at pressures of base vacuum and 50 mTorr Ar. XRD analysis revealed the films had the expected B1 structure, although XPS analysis showed a significant oxygen content. Tribological studies were conducted using a ball-on-disk test, and the wear behavior depended on the surface condition and film composition. One TiCNC film exhibited little wear but caused significant ball wear, indicating mixed carbide films are promising candidates for wear-resistant coatings.

We present an in situ study of the growth of boron nitride thin films by real time ellipsometry. Films were produced in a PECVD reactor by rf glow discharge decomposition of ammonia (pure) and diborane (1% in hydrogen), on Ni-Cr coated c-Si substrates placed either on the powered electrode or on the grounded electrode of the reactor. A fast phase-modulated ellipsometer performed the real time monitoring of the growth processes at 350 nm. The ellipsometric angle trayectories were obtained through an autocalibrated method, especially suitable for the in situ optical analysis of transparent thin films. We applied several thin film growth optical models (homogeneous, two-layer, surface roughness) to analyze parameters of the films such as refractive index, extinction coefficient, roughness and deposition rate. In all the cases studied, the two-layer model fits well with the ellipsometric measurements, but a more sofisticated model considering a variable refractive index could better describe these films.

Covalent carbon nitride films have been synthesized by laser ablation and ion-beam coprocessing. Different laser ablations give different ablated graphite plasma. Beta- C3N4 polycrystalline has been found in the deposited films. Under laser energy of 50 mJ per pulse, the adoption of 532 nm laser used for ablation of graphite is proposed for the purpose of production of good carbon nitride films. The C-N crystal structures can be improved by followed ion-beam processing.

Crystalline carbon nitride films have been synthesized in a rf plasma assisted hot filament chemical vapor deposition system. Large crystalline grains up to ∼10 μm in size as well as film-like regions are observed in the morphology of the films. β-C3N4 with two groups of lattice parameters ( one is consistent with the theoretical value and the other is 3% smaller) in the deposited films on polycrystalline Ni substrate has been revealed by x-ray diffraction spectrum (XRD). No Raman shift peaks have been found evidently by Raman scattering measurement, but some presently unknown diffraction peaks appeared in the XRD spectrum. It is proposed that there are possible unknown structures of crystalline C-N in the films. Heteroepitaxial growth of crystalline β-C3N4 has also been tried via a buffer layer of α-SiC on Si (100) substrate. The XRD pattern of a film show that there are only two main peaks at 2.79 Å and 1.87 Å corresponding to the (200) and (300) crystalline planes of the theoretical β-C3N4 The two main peaks indicate heteroepitaxial growth along the (100) direction of β-C3N4.

We attempted to deposit carbon nitride films on flat Si (111) substrates and on sharp <111>-oriented silicon needles in a radio frequency (rf) inductively coupled plasma system utilizing a graphite source and a nitrogen plasma. The resultant polycrystalline films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS). Both selected area electron diffraction (SAED) and lattice imaging were used to identify and characterize the particles, which grew as faceted crystals up to 1 Rm in size. From SAED, high resolution TEM, and EELS, it was found that the particles on the Si needles were α-Si3N4 and that those on the Si wafer were mostly β-Si3N4 and β-C3N4, with some β-C3N4 possible. Auger quantitative analysis suggests that β-C3N4 could be stabilized by the presence of silicon, resulting in a material with compositions CxSiyNz.

The two most common and most studied forms of SiC are 6H-SiC and 3C-SiC. The 3C-SiC, or cubic modification shares the zincblend lattice structure with other well developed semiconductor materials, such as GaAs and InP. We have grown thick 3C-SiC by the sublimation method. Our results show that it is possible to maintain the 3C polytype even at growth temperatures of 2000°C. Using the sublimation technique we have obtained growth rates as high as 130 microns/hr.

In order to ensure reproducible and reliable SiC semiconductor device characteristics, controlled dopant incorporation must be accomplished. Some of the many factors which greatly influence dopant incorporation are the site-competition effect, SiC(0001) substrate polarity, substrate temperature, and the dopant-source reactor concentration. In this paper, dopant incorporation is considered and compared for various dopants in the context of dopant incorporation efficiency. By using secondary ion mass spectrometry (SIMS), the relative dopant incorporation efficiencies were calculated by dividing the SIMS determined dopant concentration in the resulting epitaxial layer by the intentional gas phase dopant concentration used during the SiC CVD. Specifically, the relative magnitudes of dopant incorporation efficiencies for nitrogen, phosphorus, and boron in 6H-SiC (0001) Si-face epitaxial layers are compared as a function of the site-competition effect and the dopant-source reactor concentrations. This serves as a first approximation for comparison of the relative “doping potencies” of some common dopants used in SiC CVD epitaxial growth.

We have grown thin films of SiC by pulsed laser deposition on silicon (100) and vicinal and non-vicinal 6H SiC (0001) substrates using a quadrupled YAG laser and a high purity dense polycrystalline SiC target. Epitaxy on all three substrate types was confirmed by x-ray diffraction, transmission electron microscopy and electron diffraction. Composition of the films was measured by Rutherford backscattering spectrometry and Scanning Auger Microprobe.

Optically transparent SiC deposits were grown via atmospheric pressure chemical vapor deposition (APCVD) on graphite substrates from methyltrichlorosilane (MTS) in hydrogen in a cold-walled, RF-induction furnace. Structural morphology was examined by scanning electron microscopy and correlated to substrate temperature, MTS/H2 ratio, and hydrogen flow. Photoluminescence revealed that high quality cubic material was grown. The PL spectra exhibited a zero phonon line (2.3787 eV) attributable to an exiton bound to a neutral nitrogen donor, in addition to TA, LA, TO, and LO phonon replicas. Observed broadening and splitting of the PL spectral lines was associated with the morphological habit and internal strain of individual crystallites. In addition, the PL spectra for samples grown at higher MTS/H2 ratios and low H2 flows exhibited weak shoulders on the low energy side of the five-line spectra which might be associated with nonstoichiometric defects such as Si interstitials or C vacancies.

This paper addresses the initial stage of epitaxial growth of SiC on thin (about 300A) and thick (2000Å) Si films. Our results as obtained by Rutherford backscattering spectroscopy (RBS), Auger spectroscopy, and plan-view/cross-sectional TEM, demonstrate epitaxial growth of 3C-SiC structures on ultrathin Si films (even under non-optimized growth conditions). These preliminary results indicate that the crystalline quality of SiC on thin SIMOX is better than that grown on thick SIMOX or bulk Si substrates. Growth of SiC epi on thin Si will pave the way for growth of SiC directly on SiO2 (a compliant substrate) by carbonization of the entire thin Si top layer of SIMOX.

The extreme thermal, mechanical, corrosion resistant and electronic properties of SiC provide multiplicative combinations of attributes which allow a variety of products for very different applications. The emphasis herein will be the consideration of both the constant stress creep properties of several types of polycrystalline SiC materials and the characteristics of different SiC-based devices having high power, high frequency and switching applications and which are operational at ≥573K. The controlling mechanism in reaction-bonded SiC within the ranges of temperature and stress of 1848K-1923K and 110–220 MPa, respectively, is glide/climb controlled by climb. The controlling creep mechanism in CVD material at T<1873K is dislocation glide controlled by the Peierls stress; above this temperature, the evidence suggests that dislocation glide/climb controlled by climb becomes an increasingly important mechanism. For sintered α-SiC within the respective temperature and stress ranges of 1670K-2073K and 138–414 MPa, the controlling creep mechanisms are grain boundary sliding accommodated by grain boundary diffusion at T<1800K and lattice diffusion at T> 1920K. By contrast, the continual development of SiC thin film deposition and the device related technologies of doping, contacts and dry etching have culminated in a host of microelectronic devices operable at high temperatures, namely, MOSFET high power devices, MESFET high frequency devices, and switches including p-n junctions and thyristors. The properties of selected devices and circuits made from them are described with an emphasis on their operation at high temperature.

To assess the adhesion of nitride coatings on metals, titanium 6% aluminum 4% vanadium substrates were coated with titanium nitride (TiN) using both cathodic arc and electron beam evaporation. Titanium aluminum nitride ((Ti, Al)N) was also deposited using cathodic arc evaporation. The interfaces of the coated samples were loaded in tension using a high speed shock wave which caused spallation either at the interface, in the coating or in the metal. Scanning acoustic microscopy analysis of the spalled samples detected delaminations at the interface in the samples deposited by cathodic arc evaporation. DYNA2D modeling of plate impact spallation experiments revealed the tensile adhesion strength for TiN deposited by both techniques was ≈ 2.0 GPa. The tensile adhesion strength for (Ti, Al)N was less than 1.5 GPa.

Chemically inert ceramic coatings are currently being investigated to extend the lifetime of metallic components operating in severe environments. Polycrystalline ZrN and amorphous SiC coatings were deposited by cathodic arc evaporation and by PACVD, respectively, on Titanium Grade 12 and Incoloy 825 metal substrates. The structure of the coatings was verified by SEM and XRD. Residual stress analyses were performed on the ZrN coatings via XRD using the sin2 φ method. Compressive stresses of 3.7 GPa and 2.5 GPa were calculated in the ZrN on the Incoloy and Titanium substrates, respectively. Studies of the interfacial chemistry via AES revealed chemically abrupt interfaces. Scratch tests were employed to assess the critical load for interfacial failure and fracture mechanisms for the various coating systems. Critical loads, charaterized by a kidney-shaped crack patterns found in the scratch tracks, occurred at 12 N for ZrN on Titanium and 20 N for ZrN on Incoloy. Interfacial failure of SiC on Titanium was dominated by brittle fracture of the SiC coating at 3N loads.

The hydrolytic stability of aluminum nitride (AlN) is an important issue from the standpoint of technology development of AlN as an electronic packaging material. Although numerous studies have been made of the hydrolysis of AlN and characterization of the reaction products, an understanding of the interaction between surface sites and molecular species is still lacking.

A combination of Magic-Angle-Spinning Nuclear Magnetic Resonance (MAS NMR) and in-situ Fourier Transform Infrared (FTIR) spectroscopies was used to study the surface reactivity of AlN. The specimens used were specially fabricated self-supported AIN films of high-surface-area (∼25 m2/g), made by nitridation of sol-gel derived pseudoboehmite (AIO(OH)). The in-situ FTIR spectra suggest the formation of a surface layer on the AlN films upon storage. MAS NMR was used to further characterize the surface layer. Using the chemical shifts obtained by 1H-27Al Cross Polarization (CP) MAS NMR experiments, we were able to identify the surface cation sites. The assignment of these sites to Al3+ cations in either tetrahedral coordination with nitrogen or octahedral coordination with oxygen was used to monitor the evolution of the surface upon exposure to the atmosphere. The results indicate that high-surface-area AlN rapidly acquires a surface layer (probably AlO(OH)/Al(OH)3) upon exposure to the atmosphere.

Silicon oxynitride (Si2N2O) ceramics were oxidized in 1 atm dry oxygen at 11 00IC and 13000C. The oxidized samples were studied using x-ray photoelectron spectroscopy and crosssectional transmission electron microscopy in conjunction with energy dispersive x-ray analysis. TEM characterization revealed the chemical abruptness of the SiO2 and Si2N2O interface. Further investigation indicated the inclusions of residual SiO2 in Si2N2O, which contributed to the broad XPS elemental distribution in the oxide-substrate interface region.

Deposition of elemental S on Si(100)2×1 surfaces at room temperature changes the reconstructed Si(100)2×1 to its original bulk-terminated Si(100)l×l surface. Sulfur forms initially a (2×l) on the Si(100)2×l surface and subsequently a (l×1) on the Si(100)l×l. Above 1ML, sulfur is diffused into the Si bulk near the surface. The sticking coefficient of S on Si(100) surface is constant up to 2 ML. Deposition of S at RT up to 1 ML increases the work function of the surface by about.3±0.05 eV. Above I ML, as the S is diffused into the Si bulk, the work function decreases.

A ternary titanium aluminide alloy, Ti-46Al-3Cr (at%), was discontinuously reinforced with 5 vol% titanium diboride (TiB2), by an in-situ synthesis technique, resulting in a two phase γ(TiAl) (mainly) and α2(Ti3Al) matrix with randomly dispersed TiB2 particle. Interfaces of TiB2-TiAl were investigated by Analytical Electron Microscopy (AEM) and High Resolution Electron Microscopy (HREM). No consistent crystallographic orientation relationship was observed between TiB2 particle and TiAl matrix, and there was no evidence of alloying elements (such as Cr) segregation or interphase formation at the TiB2-TiAl interface. HREM results indicated that no semi-coherent interface between TiB2 and TiAl has been observed. There existed a thin amorphous layer (0.5 to 1.3 nm) at the TiB2-TiAl interface, which may accommodate the large lattice misfit across the interface and enhance the interfacial bonding.