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1.
B-doped a-Si 1−xC x:H films for a window layer of Si thin film solar cells have been prepared by the Cat-CVD method. It is found that C is effectively incorporated into the films by using C 2H 2 as a C source gas, where an only little C incorporation is observed from CH 4 and C 2H 6 under similar deposition conditions. Using a-Si 1−xC x:H films grown from C 2H 2, heterojunction p–i–n solar cells have been prepared by the Cat-CVD method. The cell structure is (SnO 2 Asahi-U)/ZnO/a-Si 1−xC x:H(p)/a-Si:H(i)/μc-Si:H(n)/Al. The obtained conversion efficiency was 5.4%. 相似文献
2.
We have investigated the stress behaviors and a mechanism of void formation in TiSi x films during annealing. TiSi x thin films were prepared by DC magnetron sputtering using a TiSi 2.1 target in the substrate temperature range of 200–500 °C. The as-deposited TiSi x films at low substrate temperature (<300 °C) have an amorphous structure with low stress of 1×10 8 dynes/cm 2. When the substrate temperature increases to 500 °C, the as-deposited TiSi x film has a mixture of C49 and C54 TiSi 2 phase with stress of 8×10 9 dynes/cm 2. No void was observed in the as-deposited TiSi x film. Amorphous TiSi x film transforms to C54 TiSi 2 phase with a random orientation of (311) and (040) after annealing at 750 °C. The C49 and C54 TiSi 2 mixture phase transforms to (040) preferred C54 TiSi 2 phase after annealing over 650 °C. By increasing substrate temperature, the transformation temperature for C54 TiSi 2 can be reduced, resulting in relieved stress of TiSi 2 film. The easy nucleation of the C54 phase was attributed to an avoidance of amorphous TiSi x phase. We found that amorphous TiSi x→C54 TiSi 2 transformation caused higher tensile stress of 2×10 10 dynes/cm 2, resulting in more voids in the films, than C49→C54 transformation. It was observed that void formation was increased with thermal treatment. The high tensile stress caused by volume decreases in the silicide must be relieved to retard voids and cracks during C54 TiSi 2 formation. 相似文献
3.
Physical and electrical properties of hafnium silicon oxynitride (HfSi xO yN z) dielectric films prepared by UV ozone oxidation of hafnium silicon nitride (HfSiN) followed by annealing to 450 °C are reported. Interfacial layer growth was minimized through room temperature deposition and subsequent ultraviolet/ozone oxidation. The capacitance–voltage ( C– V) and current–voltage ( I– V) characteristics of the as-deposited and annealed HfSi xO yN z are presented. These 4 nm thick films have a dielectric constant of 8–9 with 12 at.% Hf composition, with a leakage current density of 3×10 −5 A/cm 2 at Vfb+1 V. The films have a breakdown field strength >10 MV/cm. 相似文献
4.
Crystallization by excimer-laser annealing (ELA) for hydrogenated amorphous silicon (a-Si:H) films with low hydrogen content ( CH) prepared by catalytic chemical vapor deposition (Cat-CVD) was systematically studied. From optical microscopy images, no hydrogen bubbling was observed during ELA, even without a dehydrogenation process. As the laser energy density was increased to 300 mJ cm −2, the full width at half-maximum of the Raman signal from the crystalline phase decreased to approximately 4 cm −1. This value is almost equal to or even smaller than that reported for polycrystalline Si (poly-Si) films prepared from plasma-enhanced CVD (PECVD) a-Si:H films by ELA so far. The average grain size, estimated from scanning electron microscopy, was approximately 500 nm for CH of 1.3 at.%. On the other hand, the grain size of poly-Si films prepared from PECVD a-Si:H films with a dehydrogenation process was only 200 nm. The technique using Cat-CVD films is expected to be used for fabrication of low-temperature high-mobility thin-film transistors. 相似文献
5.
We review the recent progress of Cat-CVD research in Japan since the 1st Cat-CVD conference in Kanazawa in 2000. Some groups, including ours, succeeded in realizing large-area deposition of amorphous silicon (a-Si) of approximately 1 m size, and thin film transistors (TFTs) with a mobility over several 10s of cm 2 V −1 s −1 are fabricated using Cat-CVD polycrystalline silicon (poly-Si) films. Extensive studies of in situ cleaning methods revealed that a high rate of chamber cleaning is possible in Cat-CVD systems. Solar cell research is now carried out within the New Energy and Industrial Technology Development Organization (NEDO) project, and the study of Cat-CVD Si 3N 4 films prepared at lower than 100 °C is now a Japan Science and Technology Corporation (JST) project to use them as coatings on organic devices. The feasibility of Cat-CVD for various applications has been widely demonstrated, along with further understanding of the fundamental mechanism of the Cat-CVD process. 相似文献
6.
(Ti 1−xAl x)N films were prepared on a Si wafer at 700°C from toluene solution of alkoxides (titanium tetraetoxide and aluminum tri-butoxide) in an Ar/N 2/H 2 plasma by the thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrical resistivity, and Vickers micro-hardness. Single phase TiN formed at an Al atomic fraction of 0–0.2, with a mixed TiN and AlN phase occurring up to 0.6 and single phase AlN forming above 0.8. The films had relatively sooth surfaces, 0.4 μm thick at an Al atomic fraction of 0.2, and thickened with increasing Al fraction. The atomic concentration of Ti, Al, N, O, and C determined from their respective XPS areas showed that the Ti and Al contents of the films changes with the solution composition in a complementary way. The impurities were about 10 at.% oxygen and carbon. The electrical resistivity was almost unchanged from the value of 10 3 μΩ cm at 0–0.6 Al but then suddenly increased to 10 4 μΩ cm at higher Al contents. The hardness showed a synergic maximum of about 20 GPa at an Al fraction of 0.6–0.8. 相似文献
7.
The changes of the crystallinity of μc-Si phase are studied in samples deposited with hydrogen dilution ratio, H 2/SiH 4, from 9.0 to 19.0 by hot-wire CVD (Cat-CVD). In the samples deposited at filament temperature, Tf, of 1850 °C, the crystalline fraction and the crystallite size of μc-Si phase increased with increasing the H 2/SiH 4. The carbon content, C/(Si+C), was almost constant. In the XRD patterns, the intensity of Si(1 1 1) peak decreased and that of Si(2 2 0) peak increased with increasing the H 2/SiH 4. In the samples deposited at Tf of 2100 °C with H 2/SiH 4 over 11.4, the μc-Si phase was not formed and the C/(Si+C) increased. The growth mechanism of μc-Si in hetero-structured SiC x alloy films is discussed. 相似文献
8.
Growth of large-grain polycrystalline silicon has been demonstrated using silicide-mediated crystallization of amorphous silicon (a-Si) by a pulsed rapid thermal annealing (RTA). The Ni atoms in concentration of 4.6×10 12/cm 2 on the a-Si surface were heated at 700 °C in the RTA system for 10 s, ten times with 60 s intervals between the heat pulses. The Ni atoms on a-Si aggregate together, forming NiSi 2 precipitates. The crystallization proceeds from the NiSi 2 nuclei until the neighboring crystallites collide and forms distinct grain boundaries. It was found that 3.6×10 7 Ni atoms form a seed for metal induced crystallization and the grain size was 40 μm when the Ni density was 4.6×10 12/cm 2 on the a-Si. The grain size increases with decreasing metal density on a-Si. 相似文献
9.
Cat-CVD method has been applied to the growth of Si–C and Si–C–O alloy thin films. Growth mechanism has been studied with emphasis on the effects of filament materials. Growth rates and alloy compositions were measured for W, Ta, Mo and Pt filaments at the filament temperatures ranging from 1300 to 2000 °C. Si 1−xC x films with x ranging from 0.38 to 0.7 could be grown by using single molecule source Si(CH 3) 2H 2 (dimethylsilane). Si–C–O ternary alloy films was successfully prepared by using Si(OC 2H 5) 4 (tetraethoxysilane) and Si(CH 3) 2(OCH 3) 2 (dimethyldimethoxysilane) molecules. 相似文献
10.
Using the catalytic chemical vapor deposition (Cat-CVD) method, a-Si and SiN x films have been the main focus of studies. SiO 2 films have not been studied because of the limited life of catalysts such as tungsten or molybdenum in an oxidative atmosphere. In this report, we describe oxide film preparation using an iridium catalyst. We determined the most appropriate catalyst material for the oxide film process by exposing heated materials in tetraethoxysilane (TEOS) or O 2 gas. As the result, it was confirmed that the Ir catalyst works in a slow oxidative atmosphere. Using the Ir catalyst, SiO 2 films were deposited in two gas combinations: TEOS and N 2O, and SiH 4 and N 2O. Although the SiO 2 film processed with the combination of TEOS and N 2O was stoichiometric, its breakdown voltage is not sufficient. The SiO 2 film processed with the combination of SiH 4 and N 2O showed good electrical property. 相似文献
11.
A series of 0.2–0.6 μm thick SnO x films were deposited onto borosilicate and sodalime silica glass substrates by atmospheric plasma discharge chemical vapor deposition at 80 °C. SnO x films deposited from monobutyltin trichloride contained a large percentage of SnCl 2:2H 2O, and therefore were partially soluble in water. SnO x coatings deposited from tetrabutyltin were not soluble in water or organic solvents, had good adhesion even at growth rates as high as 2.3 nm/s, had high transparency of 90% and electrical resistivity of 10 7 Ω cm. As-grown tin oxide coatings were amorphous with a small concentration of SnO 2, SnO and Sn crystalline phases as determined by grazing angle X-ray diffraction and X-ray photoelectron spectroscopy measurements. Upon annealing in air at 600 °C the resistivity of SnO x films decreased to 5–7 Ω cm. Furthermore, optical and X-ray measurements indicated that SnO x was converted into SnO 2 (cassiterite) with a direct band gap of 3.66 eV. Annealing of as-grown SnO x films in vacuum at 340 °C led to formation of the p-type conductor SnO/SnO x. The indirect band gap of SnO was calculated from the optical spectra to be 0.3 eV. 相似文献
12.
Amorphous Si (a-Si) films with lower hydrogen contents show better adhesion to glass during flash lamp annealing (FLA). The 2.0 µm-thick a-Si films deposited by plasma-enhanced chemical vapor deposition (PECVD), containing 10% hydrogen, start to peel off even at a lamp irradiance lower than that required for crystallization, whereas a-Si films deposited by catalytic CVD (Cat-CVD) partially adhere even after crystallization. Dehydrogenated Cat-CVD a-Si films show much better adhesion to glass, and are converted to polycrystalline Si (poly-Si) without serious peeling, but are accompanied by the generation of crack-like structures. These facts demonstrate the superiority of as-deposited Cat-CVD a-Si films as a precursor material for micrometer-thick poly-Si formed by FLA. 相似文献
13.
We investigate residual forms of hydrogen (H) atoms such as bonding configuration in poly-crystalline silicon (poly-Si) films formed by the flash-lamp-induced crystallization of catalytic chemical vapor deposited (Cat-CVD) a-Si films. Raman spectroscopy reveals that at least part of H atoms in flash-lamp-crystallized (FLC) poly-Si films form Si-H 2 bonds as well as Si-H bonds with Si atoms even using Si-H-rich Cat-CVD a-Si films, which indicates the rearrangement of H atoms during crystallization. The peak desorption temperature during thermal desorption spectroscopy (TDS) is as high as 900 °C, similar to the reported value for bulk poly-Si. 相似文献
14.
Thin film transistor incorporating silicon nitride (SiN x) films deposited by catalytic chemical vapor deposition (Cat-CVD) on silicon exhibit some problems such as a large-threshold voltage shift and a large hysteresis loop width of the capacitance vs. voltage ( C–V) characteristics. In this work, in order to solve these problems, the surface of the silicon substrate is catalytically nitrided before SiN x deposition. Inserting the nitridation layer, injection-type hysteresis loop of C–V curve is reduced from 1.3 to 0.05 V and large threshold voltage shift to the negative direction is reduced from 4 to 1.8 V. 相似文献
15.
(Ti, Al)N films have drawn much attention as alternatives for TiN coatings, which are oxidized easily in air above 500 °C. We have investigated the effect of Al content on the oxidation resistance of (Ti 1 − xAl x)N films prepared by r.f. reactive sputtering. (Ti1 − xAlxN films (O ≤ x ≤ 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite targets with five kinds of Al-to-Ti area ratio were used. The sputtering gas was Ar (purity, 5 N) and N2 (5 N). The flow rate of Ar and N2 gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all experiments. Substrates were not intentionally heated during deposition. The deposited films (thickness, 300 nm) were annealed in air at 600 900 °C and then subjected to X-ray diffractometer and Auger depth profiling. The as-deposited (Ti1 − xAlx)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute for Ti in lattice sites. The preferential orientation of the films changed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature increased. The thickness of the oxide layer grown on the film surface decreased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prevent further oxidation. All of the films, however, were oxidized by 900 °C annealing, even if the Al content was increased up to 0.55. 相似文献
16.
Microcrystalline phase-involved oxygen-rich a-Si:H (hydrogenated amorphous silicon) films have been obtained using catalytic chemical vapor deposition (Cat-CVD) process. Pure SiH 4 (silane), H 2 (hydrogen), and O 2 (oxygen) gases were introduced in the chamber by maintaining a pressure of 0.1 Torr. A tungsten catalyzer was fixed at temperatures of 1750 and 1950 °C for film deposition on glass and crystalline silicon substrates at 200 °C. As revealed from X-ray diffraction spectra, the microcrystalline phase appears for oxygen-rich a-Si:H samples deposited at a catalyzer temperature of 1950 °C. However, this microcrystalline phase tends to disappear for further oxygen incorporation. The oxygen content in the deposited films was corroborated by FTIR analysis revealing SiOSi bonds and typical SiH bonding structures. The optical bandgap of the sample increases from 2.0 to 2.7 eV with oxygen gas flow and oxygen incorporation to the deposited films. In the present thin film deposition conditions, no strong tungsten filament degradation was observed after a number of sample preparations. 相似文献
17.
Silicon nitride thin films have been deposited on InP-based structures at both room and high temperatures in an RF-inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) equipment. Metal insulating semiconductor (MIS) diodes have been widely investigated using either SiH 4+NH 3 or SiH 4+N 2 gas phase. I–V measurements conducted on these diodes reveal high resistivity and breakdown electric field even at low deposition temperature (50°C). Double channel (DC) High electron mobility transistors (HEMTs) have been passivated by SiN x films deposited at room temperature using SiH 4+NH 3 precursors. Passivated devices exhibit a very low drift over a 45 h period of stress under high gate-drain electric field. 相似文献
18.
In 2O 3 thin films have been prepared from commercially available pure In 2O 3 powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500°C for 24 and 1 h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500°C the films’ microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In 2O 3−x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In 2O 3 (HVTE) and nearly stoichiometric In 2O 3−x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO 2 gas (0.7–7 ppm concentration range), at 250°C working temperature. At this temperature and 0.7 ppm NO 2 the calculated sensitivities ( S= Rg/ Ra) yield S=10 and S=7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In 2O 3 films to CO and CH 4. Negligible H 2O cross has resulted in the 40–80% relative humidity range, as well as to 1 ppm Cl 2 and 10 ppm NO. Only 1000 ppm C 2H 5OH has resulted to have a significant cross to the NO 2 response. 相似文献
19.
Catalytic chemical vapor deposition (Cat-CVD) has been developed to deposit alumina (Al 2O 3) thin films on silicon (Si) crystals using N 2 bubbled tri-methyl aluminum [Al(CH 3) 3, TMA] and molecular oxygen (O 2) as source species and tungsten wires as a catalyzer. The catalyzer dissociated TMA at approximately 600 °C. The maximum deposition rate was 18 nm min −1 at a catalyzer temperature of 1000 °C and substrate temperature of 800 °C. Metal oxide semiconductor (MOS) diodes were fabricated using gates composed of 32.5-nm-thick alumina film deposited at a substrate temperature of 400 °C. The capacitance measurements resulted in a relative dielectric constant of 7.4, fixed charge density of 1.74×10 12 cm −2, small hysteresis voltage of 0.12 V, and very few interface trapping charges. The leakage current was 5.01×10 −7 A cm −2 at a gate bias of 1 V. 相似文献
20.
Thin films of polycrystalline β-FeSi 2 were grown on (100) Si substrates of high resistivity by electron beam evaporation of Si/Fe ultrathin multilayers and subsequent annealing by conventional vacuum furnace (CVF) and rapid thermal annealing (RTA) for 1 h and 30 s, respectively, in the temperature range from 600 to 900°C. X-ray diffraction, Raman spectroscopy, spectroscopic ellipsometry, resistivity and Hall measurements were employed for characterization of the silicide layers quality in terms of the annealing conditions. For the silicide layers prepared by CVF annealing, although the grain size increase with increasing the annealing temperature, the optimum temperature to obtain the higher material quality (carrier mobility of the order of 100 cm 2 Vs −1 and carrier concentration of about 1 × 10 17 cm −3) is about 700°C. At higher annealing temperatures, the quality of the material is degraded due to the presence of the oxide Fe 2O 3. In the case of the silicides prepared by RTA, the quality of the material is improved progressively with increasing the annealing temperature up to 900°C. 相似文献
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