Chemical Vapor Deposition Chamber Research Articles

Industrialization of Hot Wire Chemical Vapor Deposition for thin film applications

The consequences of implementing a Hot Wire Chemical Vapor Deposition (HWCVD) chamber into an existing in-line or roll-to-roll reactor are described. The hardware and operation of the HWCVD production reactor is compared to that of existing roll-to-roll reactors based on Plasma Enhanced Chemical Vapor Deposition. The most important consequences are the technical consequences and the economic consequences, which are both discussed. The technical consequences are adaptations needed to the hardware and to the processing sequences due to the different interaction of the HWCVD process with the substrate and already deposited layers. The economic consequences are the reduced investments in radio frequency (RF) supplies and RF components. This is partially offset by investments that have to be made in higher capacity pumping systems. The most mature applications of HWCVD are moisture barrier coatings for thin film flexible devices such as Organic Light Emitting Diodes and Organic Photovoltaics, and passivation layers for multicrystalline Si solar cells, high mobility field effect transistors, and silicon heterojunction cells (also known as heterojunction cells with intrinsic thin film layers). Another example is the use of Si in thin film photovoltaics. The cost perspective per unit of thin film photovoltaic product using HWCVD is estimated at 0.07€/Wp for the Si thin film component.

Synthesis of Iron Oxide Nanoparticles from Iron Acetylacetonate and Cyclopentadienyliron Dicarbonyl Dimer in Low Pressure Plasma — Effect of Plasma Parameters on Morphology and Magnetic Properties

Iron oxide nanoparticles are synthesized using organometallic precursors namely, iron (III) acetylacetonate and cyclopentadienyliron dicarbonyl dimer in a capacitively coupled low pressure plasma system. They are characterized using High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD), magnetization studies and Raman spectroscopy. The role of hydrogen and RF (Radio Frequency) power on the crystalline and magnetic properties of the nanoparticles is studied. Incorporation of hydrogen to the Plasma-Enhanced Chemical Vapor Deposition (PECVD) chamber during the synthesis facilitates both crystallization of iron oxide nanoparticles and reduction of carbon content in the product. The saturation magnetization of iron oxide nanoparticles synthesized using iron (III) acetylacetonate and cyclopentadienyliron dicarbonyl dimer in presence of hydrogen at 200 W RF power is higher than that synthesized in the absence of hydrogen at 50 W RF power. In case of nanoparticles synthesized using iron (III) acetylacetonate, the saturation magnetization increases from 1.5 emu g-1 to 19 emu g-1, and for the same synthesized from cyclopentadienyliron dicarbonyl dimer it increases from 3.2 emu g-1 to 22.4 emu g-1.

Investigation of isochronal annealing on the optical properties of HWCVD amorphous silicon nitride deposited at low temperatures and low gas flow rates

Hydrogenated amorphous silicon nitride (a-SiNx:H) is used as anti-reflection coatings in commercial solar cells. A final firing step in the production of micro-crystalline silicon solar cells allows hydrogen effusion from the a-SiNx:H into the solar cell, and contributes to bulk passivation of the grain boundaries. In this study a-SiNx:H deposited in a hot-wire chemical vapour deposition (HWCVD) chamber with reduced gas flow rates and filament temperature compared to traditional deposition regimes, were annealed isochronally. The UV-visible reflection spectra of the annealed material were subjected to the Bruggeman Effective Medium Approximation (BEMA) treatment, in which a theoretical amorphous semiconductor was combined with particle inclusions due to the structural complexities of the material. The extraction of the optical functions and ensuing Wemple-DeDomenici analysis of the wavelength-dependent refractive index allowed for the correlation of the macroscopic optical properties with the changes in the local atomic bonding configuration, involving silicon, nitrogen and hydrogen.

Characterization of silicon nitride layers deposited in three-electrode plasma-enhanced CVD chamber

Two series of amorphous silicon nitride films were deposited using a chemical vapour deposition (CVD) reactor with two and three electrodes. Nitrogen gas and silane diluted with argon mixture (5% SiH4 + 95% Ar) were used as the working gas. The silicon nitride films were deposited at the same time on CaF2 and aluminium-coated glass substrates at 300 °C. Changing of the injected gas ratios allowed us to shift the band gap of the films in the 1.85–5.15 eV range. From AFM analysis it was found that the samples deposited in a three-electrode chamber demonstrated lower surface roughness. The electrical measurements revealed that the samples deposited in the three-electrode CVD reactor demonstrated lower leakage current and higher breakdown voltage. The composition of layers was investigated using energy-dispersive X-ray (EDS) and Fourier transform infrared (FTIR) spectroscopies. Additionally, the composition of the deposited films was evaluated from the refractive indexes, which have been estimated by fitting the spectroscopic ellipsometry data using the Tauc-Lorenz model.

Influence of sublayer thickness on electroluminescence from a-Si:H/SiNx superlattice structures

Luminescent a-Si:H/SiNx superlattice structures (SLs) with different thicknesses of sublayers were fabricated on indium tin oxide coated glass by three electrode chemical vapour deposition chamber. Transmission electron micrograph revealed small amount of silicon nanocrystallites embedded between two SiNx sublayers. Electroluminescence (EL) and electrical properties of the SLs were investigated. The dominant current mechanism is considered to be Fowler–Nordheim tunnelling under high electric field. EL mechanism is attributed to bipolar recombination of hole–electron pairs. EL spectrum of the SLs was deconvoluted into two Gaussian peaks with a major band at around ~700nm and minor at ~560nm. EL spectra blue-shift with decreasing the thickness of a-Si:H sublayers.

Carbon nanomaterials synthesized using a spray pyrolysis method

Carbon nanomaterials were synthesized using a spray pyrolysis chemical vapor deposition system (SPCVD). By varying the reaction temperature or flow rate of the carbon source, the structure or morphology of the synthesized carbon nanocoils (CNCs) can be controlled. A vertical chemical vapor deposition (CVD) furnace with a three-stage heating zone was employed to synthesize carbonaceous nanomaterials using nano-Pd catalysts at growth temperatures of 600, 700, and 800 °C. The morphology of the synthesized carbon products and the relationship between the carbon source concentration and its yield were evaluated. The results showed that CNCs formed at a lower temperature (600 °C), whereas straight carbon nanotubes were obtained at a higher temperature (700 or 800 °C). The structure and morphology of the carbonaceous samples were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Their graphite crystallinity was analyzed using Raman spectroscopy. When the three heating zones of the vertical CVD chamber were set to different temperatures, a unique nano-carbonaceous material with a special morphology similar to an octopus tentacle was formed.

Investigation of Plasma Enhanced Chemical Vapor Deposition Chamber Mismatching by Photoluminescence and Raman Spectroscopy

Slight differences between supposedly identical process chambers are a well known problem in semiconductor manufacturing. In particular, individual plasma-aided process chambers are difficult to characterize and tune to match each other because plasma is a non-equilibrium state and can leave its “footprint” in subtle ways on a wafer. This process chamber mismatching phenomena was investigated in a dual chamber, commercial, high density plasma chemical vapor deposition system by monitoring SiO2/Si interface quality using multiwavelength room temperature photoluminescence and Raman spectroscopy. Effects on the SiO2/Si interface quality, from altering the gas flow pattern in the plasma process chamber, are also studied.

Large improvement of phosphorus incorporation efficiency in n-type chemical vapor deposition of diamond

Microwave plasma enhanced chemical vapor deposition is a promising way to generate n-type, e.g., phosphorus-doped, diamond layers for the fabrication of electronic components, which can operate at extreme conditions. However, a deeper understanding of the doping process is lacking and low phosphorus incorporation efficiencies are generally observed. In this work, it is shown that systematically changing the internal design of a non-commercial chemical vapor deposition chamber, used to grow diamond layers, leads to a large increase of the phosphorus doping efficiency in diamond, produced in this device, without compromising its electronic properties. Compared to the initial reactor design, the doping efficiency is about 100 times higher, reaching 10%, and for a very broad doping range, the doping efficiency remains highly constant. It is hypothesized that redesigning the deposition chamber generates a higher flow of active phosphorus species towards the substrate, thereby increasing phosphorus incorporation in diamond and reducing deposition of phosphorus species at reactor walls, which additionally reduces undesirable memory effects.

Curvature of Substrates is Measured by Means of a Self-Mixing Scheme

We present a new method for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> measurement of substrate camber, the deformation introduced by the epitaxial layer being grown on the substrate. Similar to the currently employed laser beam deflection method, we measure the radius of curvature from the inclination angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\alpha \) </tex-math></inline-formula> (z) of the wafer surface, during the wafer rotation under the observation window of a metal–organic chemical vapor deposition (MOCVD) chamber. But, instead of the commonly used triangulation, based on a laser plus a position-sensitive detector, we employ a noncontact self-mixing interferometric detector, based on a diode laser projecting a spot onto the wafer surface and detecting the backreflection with the laser itself. Advantage of the new method is that separation of source and detector is eliminated and a smaller MOCVD window can be used. Ultimate sensitivity is improved because the angular resolution is better than with a normal detector. The experimental data show that the range of curvature radius measurable with the new method spans from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\approx 10\) </tex-math></inline-formula> m up to >10 km.

Fast and simultaneous growth of graphene, intermetallic compounds, and silicate on Cu–Ni alloy foils

A graphene bilayer was grown on copper–nickel alloy foils (30 at-% Ni: 70 at-% Cu designated as a 30Ni–70Cu) via an inductively coupled plasma–chemical vapor deposition chamber, and was characterized. The first layer fully covered the foil, while there was partial coverage of the second layer. At the same time, the alloy catalyst produced a compound of magnesium silicate in some regions and of copper sulfide in other regions on which a graphene monolayer simultaneously grew without any discontinuity or boundaries of the 1st graphene monolayer between simultaneous growth and graphene-only growth regions. Compared with Cu foils, the alloy foils led to faster growth of the graphene film in graphene-only growth regions, while maintaining the same quality, homogeneity, and thickness uniformity as a monolayer graphene grown on Cu. Raman spectroscopy and scattering demonstrated that the 2D and D bands of the Raman spectra were in the same position for the monolayer graphene on 30Ni–70Cu regardless of the grown regions and for the graphene on the Cu with a full width at half maximum of ∼38 cm−1 ranging from 30 to 55 cm−1 of 2D, and without a D band in the spectra of the graphene monolayer and bilayer. Thus the resulting graphene growth is affected primarily by the Cu catalyst, partly by the compounds grown simultaneously with the graphene monolayer on the foil surface via thermal reactions of the impurities dissolved in the alloy matrix, and partly by the Ni. The quality of the graphene is dependent on the major composition of Cu catalyst in the alloy foils. On the other hands, the alloying element of Ni governs the growth kinetics unless the alloy foils is covered with the intermetallic compounds and silicate.

Study of thermal stability of distributed Bragg reflectors based on epitaxial rare-earth oxide and silicon heterostructures

Thermal stability of rare-earth oxide/silicon multilayer heterostructure-based distributed Bragg reflectors under typical metal organic chemical vapor deposition process temperatures with an ambience of typical process gases was studied. Gadolinium oxide or erbium oxide based two period (¼λ oxide, ¾λSi) blue light (λ = 450 nm) mirrors with Si layer on the top were annealed in H2, N2, and H2 + NH3 gases for 20 min at 1015 °C in a metal organic chemical vapor deposition chamber. Changes in the structure were analyzed using x-ray diffraction and transmission electron microscopy. Reflectivity measurements were used for evaluation of optical properties of the reflectors before and after annealing. Chemical reaction between gadolinium oxide and silicon are revealed by reduction of reflectivity of Gd2O3/Si based distributed Bragg's reflector and GdSi2-x attributed peaks detected by x-ray diffraction. No major changes were detected in the Er2O3/Si heterostructure-based reflector, indicating good chemical and crystal stability of erbium oxide.

Improved Synthesis of Carbon-Clad Silica Stationary Phases

Previously, we described a novel method for cladding elemental carbon onto the surface of catalytically activated silica by a chemical vapor deposition (CVD) method using hexane as the carbon source and its use as a substitute for carbon-clad zirconia.1,2 In that method, we showed that very close to exactly one uniform monolayer of Al (III) was deposited on the silica by a process analogous to precipitation from homogeneous solution in order to preclude pore blockage. The purpose of the Al(III) monolayer is to activate the surface for subsequent CVD of carbon. In this work, we present an improved procedure for preparing the carbon-clad silica (denoted CCSi) phases along with a new column packing process. The new method yields CCSi phases having better efficiency, peak symmetry, and higher retentivity compared to carbon-clad zirconia. The enhancements were achieved by modifying the original procedure in three ways: First, the kinetics of the deposition of Al(III) were more stringently controlled. Second, the CVD chamber was flushed with a mixture of hydrogen and nitrogen gas during the carbon cladding process to minimize generation of polar sites by oxygen incorporation. Third, the fine particles generated during the CVD process were exhaustively removed by flotation in an appropriate solvent.

The novel chamber hardware design to improve the thin film deposition quality in both 12″ (300 mm) and 18″ (450 mm) wafers with the development of 3D full chamber modeling and experimental visual technique

The thin film deposition property and the process difference during the wafer size migration from 12″ (300mm) to 18″ (450mm) in the Chemical Vapor Deposition (CVD) equipment is improved and reduced, respectively, when the chamber hardware is designed with the help of 3D full chamber modeling and 3D experimental visual technique developed in this work. The accuracy of 3D chamber simulation model is demonstrated with the experimental visual technique measurement. With the CVD chamber hardware design of placing the inlet position and optimizing the distance between the susceptor edge and the reactor wall, the better thin film deposition property and the larger process compatibility during the wafer size migration from 12″ (300mm) to 18″ (450mm) for the industry cost reduction can be achieved. Non-dimensional Nusselt parameter is also found to be the effective indicator to monitor the thin film deposition property.

Nanocrystalline silicon deposition at high rate and low temperature from pure silane in a modified ICP-CVD system

An inductively coupled plasma (ICP) chemical vapor deposition (CVD) chamber has been modified to include a grounded, perforated, separator plate below the high density plasma source. A low-temperature (150 °C) ICP-CVD process for nanocrystalline Si (nc-Si) deposition has been developed using the modified plasma chamber. The separator plate causes an increase in hydrogen partial pressure from the species released from the deposit on itself and also minimizes the ion bombardment of the substrate placed on the grounded electrode below it. As a result, nc-Si deposition was achieved with high growth rates (>6 Ås−1) and without having to dilute the SiH4 precursor gas with H2. The films are characterized by Raman spectroscopy, x-ray diffraction, and photo-conductivity measurements. The developed process, scalable to large areas, is advantageous for devices with large area and flexible electronics such as solar cells and thin-film transistors.

The novel chamber hardware design to improve the thin film deposition quality in both 12″ (300 mm) and 18″ (450 mm) wafers with the development of 3D full chamber modeling and experimental visual technique

The thin film deposition property and the process difference during the wafer size migration from 12″ (300 mm) to 18″ (450 mm) in the Chemical Vapor Deposition (CVD) equipment is improved and reduced, respectively, when the chamber hardware is designed with the help of 3D full chamber modeling and 3D experimental visual technique developed in this work. The accuracy of 3D chamber simulation model is demonstrated with the experimental visual technique measurement. With the CVD chamber hardware design of placing the inlet position and optimizing the distance between the susceptor edge and the reactor wall, the better thin film deposition property and the larger process compatibility during the wafer size migration from 12″ (300 mm) to 18″ (450 mm) for the industry cost reduction can be achieved. Non-dimensional Nusselt parameter is also found to be the effective indicator to monitor the thin film deposition property.

Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on &lt;100&gt; silicon wafers

In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>−oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm−2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors.

SF6 usage and emission trends in the TFT-LCD industry

Several fluorinated compounds (FCs) used in electronics manufacturing, including SF6, perfluorocarbons (PFCs), and hydrofluorocarbons (HFCs) are extremely potent greenhouse gases. These compounds are classified as global warming pollutants to be controlled by the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol. Thin film transistor liquid crystal display (TFT-LCD) manufacturing is a major source of SF6 emissions, in which these gases are used for equipment cleaning and plasma etching. The respective Environmental Protection Administration of the Republic of China, Taiwan and the Environmental Protection Agency of the United States collaboratively strive in encouraging high technology manufacturers to improve annual reporting of FCs emissions and implement emission reduction practices and technologies.In the TFT-LCD industry, FCs account on average for 30% of total greenhouse gas emissions; 80% of emissions originate from the etching process and 20% from the chemical vapor deposition (CVD) chamber cleaning process, which is in compliance with Taiwan EPA data reports from 2005 to 2010. The leading TFT-LCD manufacturers are Japan, Korea, and Taiwan. The World LCD Industry Cooperation Committee (WLICC) subsequently established an aggressive climate protection action plan in 2001. This study focuses specifically on SF6 usage and emission factors reflecting common TFT-LCD manufacturing practices.

Effect of CO on Ru Nucleation and Ultra-Smooth Thin Film Growth by Chemical Vapor Deposition at Low Temperature

Ruthenium was deposited on SiO2/Si(001) substrates at 473 K by chemical vapor deposition (CVD) using triruthenium dodecacarbonyl with and without an overpressure of CO. Carbon monoxide was employed to inhibit the growth of previously nucleated islands to allow the formation of additional nuclei. Carbon monoxide also competed with the precursor for free hydroxyl sites on SiO2 sites where precursor adsorption and decomposition is favored. Total pressure was maintained at 84 mTorr, and CO was introduced at partial pressures of 2.5 and 8.4 mTorr at various intervals during 15 min growth runs. The nucleation density decreases with increasing CO overpressure when CO and precursor are injected simultaneously from the beginning; in this case, CO blocks the free hydroxyls where the Ru precursor dissociates. When 8.4 mTorr CO is introduced for 5 min to the CVD chamber after a 10 min period of deposition without CO, the maximum nucleation density was achieved (16.4 × 1011/cm2), which is twice as much as the Ru parti...

Catalyst-assisted vertical growth of carbon nanotubes on Inconel coated commercial copper foil substrates versus sputtered copper films

We have compared the growth of multi-walled carbon nanotubes using thermal chemical vapor deposition (CVD) on two types of substrates, copper foils and sputtered copper films. In both cases an initial 12nm thin film of Inconel is first deposited on the Cu before growing the nanotubes. The Inconel thin film can act as both a catalyst for nanotube growth as well as a support for the additional Fe catalyst that is supplied in the form of ferrocene during CVD growth. The surfaces of the underlying copper substrates are very different and play a role in the resulting carbon nanotube density. A quantitative analysis of the density and alignment of the resulting carbon nanotubes using scanning electron microscopy shows that the smooth surface of the sputtered copper substrate leads to improvement in vertical growth and density of nanotubes as opposed to the much rougher electropolished Cu foil. We show that this is related to the differences in catalyst islands distributions and graphitic crystallinity seen on the surfaces of the two types of substrates after heating the samples in the CVD chamber. This demonstrates that the surface of the starting substrate plays an important role in the subsequent catalyst surface distribution and therefore the resulting nanotube density.

Characteristics of Silicon Nanowire Field Electron Emission

Silicon nanowires with fine tip curvature and high aspect ratio are the promising alternative as the electron emitter to promote field electron emission characteristics. The fabrication of silicon nanowires based on the vapor-liquid-solid (VLS) mechanism was performed in the low pressure chemical vapor deposition chamber in the present work. The gold has its lower eutectic point than other materials and deposited on silicon wafer as the catalyst for silicon nanowire synthesis. The structural properties of the nanowires, including number density, size, aspect ratio and tapering geometry, were optimized by various experimental recipes. The results showed that the low turn-on filed of the nanowire was comparable with the published materials. The 1.2 V/μm low turn-on field was detected from the silicon nanowires which have high aspect ratio and tapered tip emitter when the silicon nanowires were synthesized under the reaction conditions at 620 °C grown for 60 minutes with silane and nitrogen flow rates at 100 SCCM.