Pressure Chemical Vapor Deposition System Research Articles

TiO2 DLAR coatings for planar silicon solar cells

AbstractIn this paper we demonstrate that a double‐layer anti‐reflection (DLAR) coating can be fabricated using only titanium dioxide (TiO2). Two TiO2 thin films were deposited onto planar silicon wafers using a simple atmospheric pressure chemical vapour deposition (APCVD) system under different deposition conditions. Weighted average reflectances of 6.5% (measured) and 7.0% (calculated) were achieved for TiO2 DLAR coatings in air and under glass, respectively. An increase in the short‐circuit current density of Δ Jsc = 2.5 mA/cm2 can be expected for an optimised TiO2 DLAR coating when compared with a commercial TiO2 single‐layer anti‐reflection coating. Copyright © 2003 John Wiley & Sons, Ltd.

LPCVD of tungsten by selective deposition on silicon

Tungsten has been deposited in a low pressure chemical vapor deposition (LPCVD) system by silicon reduction of WF6. Hydrogen passivation of the silicon was found essential to inhibit native oxide formation on the silicon. A self-limiting W thickness of 100 nm was achieved at a deposition temperature of 440 °C. A typical layer sheet resistance of 2 Ω/□ was obtained. Layers deposited at higher temperature yielded greater thickness, but showed the inclusion of higher resistivity β phase W.WSi2 also observed, indicating solid phase reaction between the silicon and the deposited W. A reduced self-limiting thickness of W was observed when heavily doped single-crystal substrates were employed. This reduction in thickness was also observed when polycrystalline samples were employed.

A Study on unique Crystal Morphology observed in the Polycrystalline Copper CVD

ABSTRACTNanostructure copper whisker growth was observed in an atmospheric pressure chemical vapor deposition (CVD) system, which used copper acetylacetonate vapor and 10-15 torr of water vapor as reactants, with 0.04-0.10 torr of chromium acetylacetonate vapor added as growth promoting catalyst. Water vapor initiated nucleation of these helical, spiral shape Cu(111) and (200) polycrystalline whiskers. While chromium acetylacetonate accelerated the growth rate. Copper whiskers had radii from 0.1 to 0.24 μm, lengths from 1 to 10 μm, and distribution density of 0.20-3.6 whiskers/μm2. Dependence of such whisker characteristics on temperature, partial pressures of H2O and chromium acetylacetonate was used to construct a kinetic model. From the Arrhenius equation, data analysis for whisker growth rate against deposition temperature showed that the activation energy for whisker growth along radial direction is 12.4 kcal/mol, and 19.6 kcal/mol for growth along axial direction. Based on such data and SEM observations, a base vapor-liquid-solid (VLS) model involving BCF theory was proposed to describe the governing mechanism for the axial growth. This model interpreted the competitive growth phenomena in both radial and axial directions, and controlling steps for radial and axial growth being assigned to mass transfer and surface reaction, respectively.

Epitaxial growth of Si1−x−yGexCy film on Si(100) in a SiH4-GeH4-CH3SiH3 reaction

Epitaxial growth of Si1−x−yGexCy epitaxial films on Si(100) has been investigated at 550°C in a SiH4-GeH4-CH3SiH3-H2 gas mixture using an ultraclean hot-wall low pressure chemical vapor deposition (LPCVD) system. With increasing CH3SiH3 partial pressure, the deposition rate decreases depending on the Ge fraction, the C concentration increases linearly up to about 1021 cm−3, and the Ge fraction increases at a high CH3SiH3 partial pressure. These characteristics can be explained by the modified Langmuir-type formulation with the assumption that CH3SiH3 is adsorbed more preferably at the Si-Ge pair site, suppressing SiH4 and GeH4 adsorption. The electrical characteristics of the P-implanted Si1−x−yGexCy epitaxial film were evaluated and it was found that electrically inactive P increases at a C concentration over 3×1020 cm−3, which corresponds to the concentration where the lattice constant deviates from that calculated using Vegard's law.

Selective Area Chemical Vapor Deposition of Si1 − xGex Thin Film Alloys by the Alternating Cyclic Method: Experimental Data: II. Morphology and Composition as a Function of Deposition Parameters

Selective area deposition of thin films, with x as large as 0.63, on oxide masked silicon wafers, was carried out in a hotwall, low pressure chemical vapor deposition system, using an alternating cyclic method described in the companion paper. Part I. In order to remove any previously deposited on the walls of the system, an HCl clean of the system was performed prior to every deposition, thereby enabling good control over the composition of the deposited films. The effect of various processing conditions, such as deposition temperature, input gas phase composition, and deposition time on the resulting film composition, morphology, and crystalline perfection were studied. For a particular film composition, there exists a morphological thickness, , at a particular deposition temperature, at which the films make a transition from smooth to rough morphology. The rough films are in a relaxed state and exhibit three‐dimensional growth. Below , the films exhibit a smooth morphology. With lowering of deposition temperature while keeping all other conditions constant, the films become richer in Ge. Thermodynamic calculations were found to be in agreement with this observation. Energy dispersive X‐ray spectroscopy using an environmemal scanning electron microscope technique was used for composition determination purpose, and transmission electron microscopy was performed to study the crystalline quality of the selectively deposited films. © 2000 The Electrochemical Society. All rights reserved.

CVD of conformal alumina thin films via hydrolysis of AlH3(NMe2Et)

Deposition of highly conformal alumina thin films has been carried out by hydrolysis of the liquid alane precursor, AlH3(NMe2Et). Depositions onto Si wafers, quartz and carbon fibres were all carried out utilizing a hot-wall atmospheric pressure chemical vapour deposition (APCVD) system. Optimum growth conditions were found to be at 165°C and with an AlH3(NMe2Et):H2O ratio of less than 1:25. Films were characterized by SEM, microprobe and electrical conductivity measurements. Growth rates were of the order of 40–80 Å min−1 at 165°C. The conformality of the films was illustrated using silicon wafers that were etched prior to deposition. Deposition onto ZnS EL-phosphor particles was accomplished in a simple fluidized-bed APCVD reactor. The deposited films were conformal and continuous. No significant reduction in the initial brightness or change in the colour balance of the phosphor was observed from the coating process. Copyright © 2000 John Wiley & Sons, Ltd.

Low Temperature Lateral Epitaxial Growth of Silicon Carbide on Silicon

ABSTRACTTo reduce the defect density inherent in conventional heteroepitaxial growth of SiC on Si, selective epitaxy followed by lateral epitaxial growth was performed in a conventional atmospheric pressure chemical vapor deposition (APCVD) system. The source gas was primarily hexamethyldisilane (HMDS). Hydrogen was used as the carrier gas and small amounts of hydrogen chloride (HCl) were added to improve the selectivity. Si(001) wafers, with an oxide layer (∼ 700 nm thick) as a mask, were used as substrates. The grown films were analyzed using optical microscopy and scanning electron microscopy (SEM). In earlier work, we had demonstrated the problems associated with the application of this technique – viz., oxide degradation and high growth temperature. Using HMDS, the growth temperature has been considerably reduced allowing the continued use of an oxide mask. Selective growth was demonstrated in films grown at 1250° and below.

Diagnostic system to determine the in-service life of dry vacuum pumps

A diagnostic system for dry pumps is proposed. It predicts future pump motor current from time-series in-situ measurements. The prediction system has been constructed using a data acquisition system with an online system identification software algorithm. A field test on a low pressure chemical vapour deposition (LPCVD) system for the silicon nitride process predicted large values of motor current, some of which correlated well with actual motor currents as the pump became clogged. The combined use of the predicted motor current and the stability criteria shows promise in predicting the actual service life of a dry pump.

Amorphous SiGe deposition by LPCVD from Si2H6 and GeH4 precursors

This paper presents results on the deposition of Si 1-x Ge x layers in a hot wall low pressure chemical vapor deposition system, using disilane and germane as source gases, and hydrogen as carrier gas. The effect of the composition of the gas (with disilane flow rates between 4 and 20 sccm, germane flow rates between 0 and 20 sccm and hydrogen flow rates between 0 and 120 sccm), the deposition temperature (between 450 and 600°C) and the total pressure (between 300 mTorr and 1 Torr) on the growth rate, composition and crystallinity of the film has been investigated. The growth rate depends linearly on the composition of the gas when a carrier gas is used, but the dependence changes to a more complicated U-shaped dependence for depositions with pure precursors atmosphere. The film composition depends mainly on the composition of the gas, but it is also affected by the precursors partial pressure. The H 2 carrier gas acts only as a dilution agent and does not affect the hydrogen desorption from the surface, which is the mechanism that limits the growth. Depositions at temperatures below 500°C produce an amorphous material but films grown at higher temperatures are polycrystalline.

Copper Chemical Vapor Deposition Films Deposited from Cu(1,1,1,5,5,5-hexafluoroacetylacetonate) vinyltrimethylsilane

Copper chemical vapor deposition (Cu CVD) from Cu(hfac)vinyltrimethylsilane was studied using a low pressure chemical vapor deposition (LPCVD) system of a cold-wall vertical reactor. It was found that the resistivity of the chemical vapor deposited Cu films was dependent on the film's microstructure and impurity content, which in turn were dependent on the deposition conditions. Using H2 as the carrier gas, we were able to deposit Cu films of low impurity content at deposition rates as high as 150 Å/min. The lowest resistivity Cu films can be deposited at a temperature of 180°C and a pressure of 300 mTorr.

The CVD growth of Cu films using H2 as carrier gas

Copper chemical vapor deposition from Cu(hexafluoroacetylacetonate)trimethylvinylsilane (Cu(hfac)TMVS) was studied using a low pressure chemical vapor deposition system of a cold wall vertical reactor. The Cu films deposited using H2 as a carrier gas revealed no impurities in the films within the detection limits of Auger electron spectroscopy and x-ray photoelectron spectroscopy. Using hydrogen as a carrier gas, the hydrogen not only acts as a reducing agent, but also reacts with the residual fragment of precursor. As a result, using H2 as a carrier gas for Cu(hfac)TMVS resulted in Cu films of lower resistivity, denser microstructure and faster deposition rate than using Ar or N2 as the carrier gas. Moreover, we found that N2 plasma treatment on the substrate surface prior to Cu deposition increased the deposition rate of Cu films.

Doping and electrical characteristics of in situ heavily B-doped Si 1− xGe x films epitaxially grown using ultraclean LPCVD

Doping and electrical characteristics of in situ heavily B-doped Si 1− x Ge x ( 0.15 < x < 0.80) films epitaxially grown on Si(110) were investigated. The epitaxial growth was carried out at 550 °C in a SiH 4-GeH 4-B 2H 6-H 2 gas mixture by using an ultraclean hot-wall low pressure chemical vapor deposition (LPCVD) system. With increasing B 2H 6 partial pressure, the deposition rate decreased only at the higher GeH 4 partial pressure, and the B concentration ( C B ) in the film increased proportionally up to 10 22 cm −3. The Ge fraction scarcely changed with the B 2H 6 addition. The carrier concentration was nearly equal to cb up to about 2 × 10 20 cm −3, and it tended to be saturated at around 5 × 10 20 cm −3 at C B < ~ 10 22 cm −3 . In other words, electrically inactive B increased with increasing C B above 2 × 10 20 cm −3. The resistivity decreased with increasing carrier concentration at c b <~ 10 22 cm −3 and was influenced by alloy scattering. Discrepancy of the lattice constants from Vegard's law was observed at higher cb in the order of 10 20 cm −3 and above, which corresponded with the saturation of the carrier concentration.

Chemical Vapor Deposition of Conformal Alumina Thin Films

AbstractDeposition of highly conformal alumina thin films has been carried out by hydrolysis of the liquid alane precursor, AlH3(NMe2Et). Deposition onto Si wafers, quartz and carbon fibers were all carried out utilizing a hot-wall atmospheric pressure chemical vapor deposition (APCVD) system, while deposition onto ceramic particles was accomplished in a simple fluidized-bed APCVD reactor. Films were characterized by SEM, microprobe and electrical conductivity measurements. Growth rates were on the order of 40 - 80 Å.min−1at 165 °C. The conformality of the films was illustrated using silicon wafers that were etched prior to deposition.

Selective epitaxial growth of Si1−xGex/Si strained-layers in a tubular hot-wall low pressure chemical vapor deposition system

Selective epitaxial growth (SEG) of SiGe on patterned-oxide silicon substrates, using a tubular hot-wall low pressure chemical vapor deposition (LPCVD) system, has been demonstrated. This conventional LPCVD system was proposed as a low cost alternative for SiGe epitaxial growth. Dichlorosilane (SiH2Cl2) and germane (GeH4) were used as the reactant gases with hydrogen as a carrier gas, with no addition of HCl needed to achieve selectivity in quality epitaxial growth of SiGe. Nomarski microscopy showed good selectivity with no nucleation occurring on the SiO2 areas. A low defect silicon buffer layer grown under SEG conditions was key in obtaining high-quality growth. Cross-sectional transmission electron microscopy showed that the SiGe strained layers grown at 700 °C, 750 °C, and 800 °C were of high quality.

High quality epitaxial Si grown by a simple low pressure chemical vapor deposition at 550 °C

We have designed a simple-hot wall low pressure chemical vapor deposition (LPCVD) system to grow high quality epitaxial Si films from 550 to 900 °C. The epitaxial film has been examined by scan electron microscopy for surface morphology, and by x-ray diffraction and cross-sectional transmission electron microscopy for crystallinity. Its quality has been found comparable to that of the substrate. Reduction of moisture and oxygen in the ambient is critical to the success of the growth at low temperatures. A combination of a leak-tight LPCVD reactor, a high flow rate of 61/min of H2 purge, and a pre-bake at high temperature of 950 °C has been used to achieve the reduction of moisture and oxygen. Degraded films form with increasing full width at half maximum of x-ray diffraction peak when a pre-bake at lower temperature is used.

High phosphorus doping of epitaxial silicon at low temperature and very low pressure

In situ phosphorus doped Si epitaxial layers have been grown at 600 °C in a very low pressure chemical vapor deposition system, using SiH4 and PH3 diluted in H2. The presence of H2 was found to decelerate the epitaxial growth rates. Secondary-ion mass spectrometry measurement shows that the constant phosphorus concentration with depth for a steady flow of PH3 was achieved. Namely, dopant concentration is a function of gas phase dopant concentration. Chemical concentration as high as 2.5×1020 P/cm3 was obtained in Si epitaxial layers though with very low growth rate. Epilayers with constant doping levels from 1.5×1018 P/cm3 to 1.2×1020 can readily be grown. Despite the relatively low growth rate, there is no evidence of a time-dependent accumulation of phosphorus on the growth surface or the reactor wall. The reasons accounting for this phenomenon are discussed.

Selective Epitaxial Growth of Strained Silicon-Germanium Films in Tubular Hot-Wall Low Pressure Chemical Vapor Deposition Systems

AbstractSelective epitaxial growth (SEG) of silicon-germanium (SiGe) films on patterned-oxide silicon substrates, using a tubular hot-wall low pressure chemical vapor deposition (LPCVD) system, is demonstrated in this study. This conventional system is proposed as a low cost alternative for SiGe epitaxial growth. Three process improvements needed to achieve quality growth are discussed. First, the hydrogen bake process is modified to eliminate Ge-outgassing. Secondly, a Si SEG buffer layer is deposited prior to SiGe SEG. Finally, a small flow of dichlorosilane is introduced during the temperature ramp-down period prior to SiGe SEG. The growth results are discussed in terms of growth selectivity, thickness uniformity, growth rate, defect density, SiGe film composition, and electrical properties.

Low pressure chemical vapor deposition of molybdenum oxides from molybdenum hexacarbonyl and oxygen

Thin films of molybdenum oxides were deposited at 300–500 °C and 200–1014 m Torr (26.6–135 Pa) from Mo(CO)6, O2, and H2O using an inductively heated low pressure chemical vapor deposition system. Two oxygen gas flow rates of 5 and 15 sccm were used. α-MoO3 films were deposited at temperatures of 425–450 °C, pressures of 660–1014 m Torr (88.0–135 Pa), with an O2 flow rate of 5 sccm; and at 450–500 °C, 300–500 m Torr (40.0–66.7 Pa), with an O2 flow rate of 5 sccm. The polycrystalline films were deposited on silicon (100) wafers and exhibited preferred orientations. Gas phase decomposition of the precursor was significant with temperatures ≫400 °C and pressures ≫600 m Torr (88.0 Pa), with an O2 flow rate of 15 sccm. Owing to decomposition of the precursor in the gas phase and low gas velocities, the films decreased in thickness in the direction of flow. Thermodynamic equilibrium calculations indicated that α-MoO3 was the most stable phase for all deposition conditions. However, α-MoO3 was deposited only at high temperatures and pressures. A quadratic model of α-MoO3 formation was developed using experimental design for the 5 sccm deposition data as a function of temperature and pressure. Both parameters were significant in the formation of α-MoO3 films. The films were characterized using X-ray diffraction and X-ray photoelectron, Auger, and laser Raman spectroscopies.

Novel Oxygen Free Titanium Silicidation (OFS) Processing for Low Resistance and Thermally Stable SALICIDE (Self-Aligned Silicide) in Deep Submicron Dual Gate CMOS (Complementary Metal-Oxide Semiconductors)

A low resistance and thermally stable TiSi2 self aligned silicide (SALICIDE) for deep submicron p+ and n+ dual gate complementary metal-oxide semiconductors (CMOS) has been developed. This was achieved through the use of a novel oxygen free silicidation (OFS) process using a reaction between a titanium included nitrogen ( Tix Ny ) and an oxygen free poly-Si-gate. The oxygen free poly-Si was realized using low pressure chemical vapor deposition (LPCVD) system with nitrogen flow Load-Lock chamber. The OFS TiSi2 film did not agglomerate after the treatment of the RTA at 1050° C for 20 s in a N2 atmosphere and the additional furnace annealing at 900° C for 30 min. in a N2 atmosphere. For both n+ and p+ gates, low sheet resistances (about 2.8 Ω /square.) were achieved under the 0.2 µ m size.

High temperature deposition of SiN films using low pressure chemical vapor deposition system for x-ray mask application

SiN films for x-ray mask membranes were prepared using a low pressure chemical vapor deposition system designed for high temperature deposition and low impurity incorporation. The physical and optical properties of the films such as stress, uniformity, optical transmittance, and absorption were investigated. Film composition and impurities were also evaluated. The SiN film deposited at a substrate temperature of 1000 °C showed suitable properties for x-ray mask membrane, such as well controlled tensile stress of about 5×107 Pa, high optical transmittance over 95% at 500 to 800 nm, and low impurity concentration.