Polycrystalline β-SiC, with grain size up to 0.2 μm, was grown on silicon substrate by electron cyclotron resonance chemical vapor deposition (ECR-CVD) from SiH4/CH4/H2 at 178–500 °C. The nucleation process and surface structure of polycrystalline SiC were investigated via observing the film surface by atomic force microscopy (AFM). Reaction species which promote polycrystalline SiC was in-situ monitored by quadruple mass spectrum analysers during deposition process, which is crucial for the control of polycrystalline SiC growth. The microstructure of SiC films were inspected by bright-field imaging, dark-field imaging, and electron diffraction in cross-sectional transmission electron microscopy. This paper will also discuss the key parameters for the nucleation and growth of polycrystalline β-SiC at very low temperature in ECR-CVD system.

The results show that unlike those made by physical vapour deposition, Ti(C,N) coatings made by plasma assisted chemical vapour deposition are composed of two phases, TiN and TiC. With the formation of two phases, the columnar structure vanishes gradually and the crystal size becomes small. The carbon content is the dominant controlling factor for a linear increase in microhardness of the coatings, but the residual macrostress and the adhesive strength evaluated under cyclic contact conditions are dependent to a great extent on the percentage of the two phases. There is an intermediate carbon content for the present Ti(C,N) coatings which yields a fine mixed microstructure and optimum mechanical properties.

Transition metal of nitrides have many desirable properties for application at elevated temperatures because of extremely high melting point, hardness, high temperature strength, good thermal shock resistance, and high thermal conductivity. We have investigated the thin film coatings of nitrides (titanium nitride, and composite carbon nitride) on various commercial useful substrates by the pulsed laser deposition (PLD) method. The PLD method is unique process for depositing high quality thin films with novel microstructure and properties. The laser parameters: energy density, pulse rate, target/substrate distance and substrate temperature have been optimized to improve the quality of thin films. The mechanical properties of the films have been evaluated at different processed conditions by nanoindentation technique. The films were characterized by X-ray diffraction, scanning electron microscope and FTIR techniques. Optimization of laser deposition parameters to obtain high quality thin films will be discussed in detail.

Transmission Electron Microscope (TEM) techniques are applied to study the microstructure of diamond films grown from fullerene precursors. Electron diffraction and electron energy loss spectra (EELS) collected from the diamond films correspond to that of bulk diamond. Microdiffraction, high resolution images and EELS help determine that the first diamond grains that nucleate from fullerene precursors generally form on a thin amorphous carbon nterlayer and seldom directly on the silicon substrate. Grain size measurements reveal nanocrystalline diamond grains. Cross section TEM images show that the nanocrystalline diamond grains are equiaxed and not columnar nor dendritic. The microstructure of small equiaxed grains throughout the film thickness is believed responsible for the very smooth surfaces of diamond films grown from fullerene precursors.

High resolution electron microscopy is employed to study the crystallography and morphology of zirconia nanocrystallites in zirconia-alumina nanolaminates and zirconia films. Unity volume fraction of tetragonal zirconia formed when the zirconia layer thickness was less than 6.2 nm, a theoretically predicted critical size for tetragonal-to-monoclinic zirconia (t -> m-ZrO2) transformation. In thicker layers, monoclinic zirconia formed, accompanied by renucleation and void formation which caused roughness to the zirconia nanolayers. The average position of the voids in the layers was 6.3 nm from the growth interface, coinciding with the critical dimension for t -> m-ZrO2 transformation.

Pulsed excimer-laser crystallization of amorphous silicon on non-crystalline substrates is an important processing technique for large-area polycrystalline silicon films and devices. Interest stems, in large part, from proposals to use polycrystalline silicon on glass in large-area electronic applications, such as flat-panel active matrix displays and two-dimensional imaging systems. The polycrystalline silicon is envisioned to increase the functionality and reduce costs over the current circuits that use amorphous silicon. Also, it is found that laser-crystallized polycrystalline silicon exhibits some interesting materials properties, such as a sharp peak in the average grain size with large lateral grain growth as a function of excimer laser energy density. The average grain size increases with increasing laser fluence and peaks on the order of several microns or two orders of magnitude larger than the film thickness. The grain size then decreases with further increases in laser fluence. This peak in grain size is accompanied by a similar peak in the Hall electron mobility. This is a significant relationship for devices since the grain structure has a substantial influence on electrical properties. But to the detriment of device parameters, this large lateral grain growth occurs over a very arrow range of laser fluences and is accompanied by a corresponding peak in the surface roughness of the films. These relationships between laser processing conditions, materials properties, and device parameters force a compromise between large grain size for high mobility and homogeneity of material for uniformity of device characteristics. A window does exist in process parameter space where good-quality devices with uniform characteristics have been obtained. In addition, these attributes have been achieved under conditions that yield good polycrystalline silicon and good amorphous silicon devices on the same wafer within a mm of one another, allowing for hybrid polycrystalline and amorphous silicon circuits.

We have found, for excimer laser crystallized poly-Si thin films, that there are two different grain growth processes that depend on the energy density. Columnar grains grow laterally at lower energy densities. The other grain growth process at higher energy densities is shown to be secondary grain growth caused by a less oriented structure with fine granular grains. A TFT with the maximum mobility is obtained at the border for the lower energy grain growth. Grain boundary and intragrain defects around grain boundary formed through the secondary grain growth reduce the mobility in spite of considerable grain enlargement.

Polycrystalline silicon is the most widely used structural material for surface micromachined microelectromechanical systems (MEMS). There are many advantages to using thick polysilicon films; however, due to process equipment limitations, these devices are typically fabricated from polysilicon films less than 3 μm thick. In this work, microelectromechanical test structures were designed and processed from thick (up to 10 μm) in situ boron-doped polysilicon films. The elastic modulus of these films was about 150 GPa, independent of film thickness. The thermal oxidation of the polysilicon induced a compressive stress into the top surface of the films, which was detected as a residual stress in the polysilicon after the device fabrication was complete.

Photonic integrated circuits in silicon require waveguiding through a material compatible with silicon VLSI technology. Polysilicon (polySi), with a high index of refraction compared to SiO2 and air, is an ideal candidate for use in silicon optical interconnect technology. Inspite of its advantages, the biggest hurdle to this technology is that losses of 350dB/cm have been measured in as-deposited polySi waveguide structures, as against ldB/cm losses measured in waveguides fabricated in crystalline silicon. We report methods for reducing scattering and absorption, which are the main sources of losses in this system. To reduce surface scattering losses we fabricate waveguides in smooth recrystallized amorphous silicon and Chemo-Mechanically Polished (CMP) polySi, both of which reduce losses by about 40dB/cm to 15dB/cm. Atomic Force Microscopy (AFM) and spectrophotometry studies are used to monitor surface roughness which has been reduced from an RMS roughness value of 19–20nm down to about 4–6nm. Bulk absorption/scattering losses can depend on size, structure, and quality of grains and grain boundaries which we investigate by means of Transmission Electron Microscopy (TEM). Although the lowest temperature deposition has twice as large a grain size as the highest temperature deposition, the losses appear to not be greatly dependent on grain size in the 0.1pm to 0.4pm range. Additionally, absorption/scattering at dangling bonds is investigated before and after a low temperature Electron-Cyclotron Resonance (ECR) hydrogenation step. After hydrogenation, we obtain the lowest reported polySi loss values at λ = 1.54μm of about 15dB/cm.

In this work, polycrystalline SiGe has been viewed as an alternative gate material to polysilicon in single wafer processing for the deep submicrometer VLSI applications. We studied deposition of the silicon-germanium (SiGe) films with different germanium concentrations (up to 85%) on SiO2 in a rapid thermal chemical vapor deposition reactor using GeH4 and SiH4/H2 gas mixture with the temperature ranging from 550°C to 625°C. Since the SiGe RTCVD process is selective toward oxide and does not form nucleation sites on the oxide easily, an in-situ polysilicon flash technique is used to provide the necessary nucleation sites for the deposition of SiGe films with high germanium content. It was observed that with the in-situ polysilicon flash as a pre-nucleation seed, the SiGe deposited on SiO2 forms a continuous polycrystalline layer. Polycrystalline SiGe films of about 2000Å in thickness have a columnar grain structure with a grain size of approximately 1000Å. Compositional analyses from Auger Electron Spectroscopy (AES) and Rutherford backscattering (RBS) show that the high germanium incorporation in the SiGe films has a weak dependence on the deposition temperature. It is also noted that the germanium content across the film thickness is fairly constant which is a critical factor for the application of SiGe films as the gate material. Lastly, we found that the surface morphology of SiGe films become smoother at lower deposition temperature.

The formation of silicon hillocks at the surface of amorphous and polycrystalline LPCVD silicon films, as a function of phosphorus doping was investigated by SEM, TEM replica and X-ray diffraction techniques. The phosphorus doping was performed in the concentration range from 9 × 1019cm-3 tol.5 × 1020cm-3. It was observed that the hillocks size increases with the dopant concentration for the as-doped and for annealed films. The experimental data were analysed in a model involving diffusion of silicon during the doping and recrystallization processes.

Polycrystalline silicon (poly-Si) films are of great interest in the field of TFT fabrication for active matrix liquid crystal display(AM-LCD) applications. Low temperature depositions below 500 °C are necessary for using a glass substrate for the application to large area devices such as display devices. We investigated poly-Si growth at low temperature by plasma enhanced chemical vapor deposition (PECVD). Cathode deposition is used in which substrates are mounted on the powered electrode and a mesh electrode is attached on the cathode for protecting the growing surface from ion impacts. It is found that poly-Si films can be deposited in the wide range of SiH4 concentration even at 100%, and a high deposition rate of 35nm/min has been realized. This investigation gives highly promising results for poly-Si growth technology at low temperature.

Conventional and Rapid Thermal Annealing of Semi-Insulating Polycrystalline Silicon layers obtained by Low Pressure Chemical Vapor Deposition (LPCVD) from disilane Si2H6 have been performed in order to determine the structural modifications induced on the layers by these thermal treatments. The study of these modifications has been carried out by several analysis methods like FTIR, XPS, TEM, RAMAN and ellipsometry. The results obtained are presented, contrasted and discussed in this work.

Single-shot ELA was performed on 45nm-thick amorphous Si films. With an increase in pulse energy density, the cystallinity improved drastically for both samples without heating and with heating at 400°C. Correspondingly, the characteristics of TFT fabricated using a low temperature process improved distinctly. The threshold voltage decreased depending on the decrease in gate voltage swing due to the improvement in crystallinity of Si films. Efficient single-pulse ELA of less than 250MJ/cm2 as the optimum condition for poly Si TFT has been attained as a result of saving an energy amount of 100mJ/cm2 by heating the substrate. Moreover, a uniform distribution of TFT characteristics across the wafer was obtained.

The solid phase crystallization behavior of argon ion (Ar+) implanted very thin polycrystalline silicon (poly-Si) films has been investigated. Poly-Si films of 500Å thickness were deposited at 625°C by low pressure chemical vapor deposition (LPCVD). The films were amorphized by Ar+ implantation with 7 ° tilt angle. The amount of ions implanted was varied from 2.0 × 1013 cm-2 to 1.2 × 1015 cm-2 and the acceleration voltages from 40KeV to 120KeV. The films were recrystallized by furnace annealing at 580°C for 48 hours in N2 atmosphere, followed by 1000°C annealing The crystallinity of the recrystallized Si films and the distribution of the argon atoms in the film were investigated. It was found that the crystallinity strongly depended on the Ar+ implantation dose. The average grain size of Ar+ implanted film was about 0.25μm, which was smaller than that of Si+ implanted film of the same dose, 0.45μm. Ar atoms retarded the grain growth rate during the annealing process and the excess Ar atoms in Si films were segregated at the surface of silicon films after 1000°C annealing Poly-Si thin film transistors (TFTs) were fabricated at high temperature using Ar+ implantation technique. Remarkable electrical characteristics (Ids- Vgs) were obtained such as an electron mobility of 35 cm2/V.s, which was attributed to the enhancement of crystallinity by Ar+ implantation. But, segregated Ar atoms near the interface would give rise to structural deformation and crystalline defects which can act as the scattering and’ trapping centers for carriers.

Thin films of an amorphous Si-B alloy with B contents 1–50% were deposited by low pressure chemical vapor deposition (LPCVD) from diborane (B2H6) and silane (SilH4) gases. XRD patterns of the as deposited films showed them to be completely amorphous. The films were annealed in N2 at 600–800°C for 30 minutes and characterized by Raman spectroscopy. Wet oxidation of the film was carried out 700°C for 30 minutes, and the films examined by XRD. The structural changes induced by B in the a-Si network discussed in the conceptual framework of the continuous random network (CRN) model. We conclude that the boron incorporation enhances the structural disorder and induces topological changes in the amorphous network.

Plasma-enhanced chemical vapor deposition was used to deposit a-Si:H thin films (∼ 1000 Å) at various temperatures below 300°C on Coming 7059 glass substrates using a silane-based plasma. These films were used as precursor materials to produce solid phase crystallized polycrystalline silicon (poly-Si) by conventional furnace annealing at 600°C in N2 ambient. The precursor a-Si and final poly-Si films were examined using spectroscopic ellipsometry and transmission electron microscopy. Precursor film deposition temperatures were found to affect the void density in the a-Si film and grain size in the resulting poly-Si film with lower deposition temperatures leading to higher void density in the a-Si film and larger grain size in the poly-Si film.

P-type polycrystalline silicon films on silicon wafers were obtained by annealing at 575 °C boron-doped amorphous hydrogenated silicon (a-Si:H) films. During the anneal, the internal stress of the film changed from compression to tension. The crystallization kinetics became faster when increasing the boron concentration. The hardness and elastic modulus of each film were determined by nanoindentation. The elastic modulus increased systematically upon crystallization. Wafer curvature monitoring during the thermal cycle allowed us to derive the thermal expansion coefficient of a-Si:H for different boron doping levels. Above a critical temperature of 320°C, the internal stress of the a-Si:H films rapidly changed toward a tensile state, independent of the boron concentration. Analysis of the hydrogen-bonding configurations by Fourier transform infrared spectroscopy indicated that this rapid stress change was due to hydrogen out-diffusion. The evolution of the internal stress with time was followed during the 575°C crystallization isothermal plateau. The circular blistering and spalling observed upon annealing in some cases of low doping levels was correlated with the presence of microvoids and with the internal stress of the a-Si:H film.

Device-quality poly-Si films are used as the active material of poly-Si thin film transistors. Poly-Si films with high crystallinity, which have large grains and/or low intragranular defects, lead to a high device performance. The presence of O or C impurities in the deposited Si films can greatly affect the behavior of crystallization and grain growth of these films, and their resulting crystallinities. A substantial amount of O or C can be introduced in the films during deposition from residual gases in the deposition chamber. Control of base pressure during Si deposition, therefore, will be an important process parameter determining the crystallinity of these films. The effects of the base pressure on the crystallization and grain growth of deposited Si films were investigated using a high vacuum Chemical Vapor Deposition system. Lower base pressure decreases the deposition temperature for the amorphous/crystalline transition of as-deposited films. Crystallization of amorphously deposited films is also affected by base pressure. The kinetics of crystallization and crystallinities of poly-Si films after crystallization are substantially increased by reducing base pressure. Enhanced crystallization kinetics and film crystallinities can be explained by reduced inclusions of O or C impurities in Si films, thus enhancing the atomic mobility. The improved film crystallinity of poly-Si films leads to higher device performance of poly-Si TFT's.

High quality polycrystalline silicon was made on glass from fluorinated precursors by two step growth, i.e., (1) formation of seed crystals on glass by layer-by-layer(LL) technique and (2) grain-growth on the seeds. In LL technique, deposition of ultra-thin films and treatment with atomic hydrogen was repeated alternately. Columnar grains with 200 nm dia were grown epitaxy-like on the seeds by optimizing the deposition parameters under in situ observation with spectroscopic ellipsometry.