Low-pressure Chemical Vapor Deposition Reactor Research Articles

Influence of dopant concentration and type of substrate on the local organization of low-pressure chemical vapour deposition in situ boron doped silicon films from silane and boron trichloride

The deposition of in situ boron doped silicon films from boron trichloride BCl 3 and silane SiH 4 in a conventional low-pressure chemical vapour deposition reactor has been studied for high boron doping levels and two kinds of substrates (SiO 2 and Si 3N 4). On the basis of transmission electron microscopy and X-ray photoelectron spectroscopy results, these films appear to be highly sensitive to the local electronic environment of both substrate and deposited atoms. Indeed, beyond a critical doping level, this material becomes more and more amorphous, due to the occurrence of a particular organization of boron atoms in the silicon matrix. This behaviour results in a lowering of the well-known boron enhancement effect for deposition rate and crystalline fraction.

Balancing reactor fluid dynamics and deposition kinetics to achieve compositional variation in combinatorial chemical vapor depositions

A low-pressure chemical vapor deposition (CVD) reactor was modified to produce compositional spreads of TiO 2/HfO 2/SnO 2 and ZrO 2/HfO 2/SnO 2 on a single Si(1 0 0) wafer. Use of anhydrous metal nitrates as single-source precursors allowed the deposition kinetics to be matched. The compositions were mapped using X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. On a single wafer, an array of capacitors each with a dimension of 100 μm×100 μm was used to map the effective dielectric constant of the films. The dielectric constant reached a maximum in the regions with the high TiO 2 or ZrO 2 content. A unique crystalline phase having the orthorhombic α-PbO 2 structure was detected in the films grown at or above 450 °C.

Combinatorial Chemical Vapor Deposition of Metal Silicate Films Using Tri(t -butoxy) silanol and Anhydrous Metal Nitrates

ABSTRACTA modified low-pressure chemical vapor deposition reactor was used to create compositional spreads of MO2/SiO2 films (M = Hf, Zr and Sn) using tri(t-butoxy) silanol and anhydrous metal nitrates of hafnium, zirconium and tin at temperatures below 250 °C. The compositional spreads formed by this process were characterized by ellipsometry and Rutherford backscattering spectrometry. A survey of possible reactions involved in the deposition is included.

Combinatorial Chemical Vapor Deposition. Achieving Compositional Spreads of Titanium, Tin, and Hafnium Oxides by Balancing Reactor Fluid Dynamics and Deposition Kinetics

A low-pressure chemical vapor deposition (CVD) reactor was modified to produce a continuous compositional spread of titanium, tin, and hafnium dioxides on a single Si(100) wafer. The corresponding anhydrous metal nitrates, Ti(NO 3 ) 4 , Sn(NO 3 ) 4 , and Hf(NO 3 ) 4 , were used as single-source precursors to the component oxides. The compositions were mapped using X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. On a single wafer an array of 100 μm x 100 μm capacitors was used to map the effective dielectric constant (κ eff ) of the films. For compositional spreads grown at 400 and 450°C κ eff reached a maximum value in regions with the highest concentrations of TiO 2 . The formation of the orthorhombic α-PbO 2 phase for a composition near Hf 0.75 Sn 0.25 O 2 was also observed in the 450°C compositional spread.

IR and Raman absorption spectroscopic studies of APCVD, LPCVD and PECVD thin SiN films

Silicon nitride films prepared by different chemical vapour deposition (CVD) techniques are studied by infrared (IR) and Raman spectroscopy. The main peak in the IR spectrum for films obtained in atmospheric pressure CVD (APCVD) and low pressure CVD (LPCVD) reactors is at 830 and at 811 cm −1, respectively, while for plasma-enhanced CVD (PECVD) films it is at 826 cm −1. For layers deposited by PECVD small peaks are observed at about 3300 cm −1 and in the region 3200–3500 cm −1 which indicates the presence of N–H and O–H bonds. Scanning electron microscopy (SEM) shows that the surface of the LPCVD samples is smoother than the surfaces of the APCVD and PECVD samples. A correlation between the layer characteristics such as the refractive index ( n), the dielectric constant ( ε), the etching rate ( v etch), the IR spectrum, etc. and the type of the deposition system is established.

Non-destructive characterization of strontium bismuth tantalate films

Optical, compositional, and structural properties of strontium bismuth tantalate (SBT) films deposited in a high throughput low-pressure chemical vapor deposition reactor using liquid metal-organic precursors were characterized using three non-destructive techniques, spectroscopic ellipsometry (SE), Rutherford backscattering spectrometry (RBS), and X-ray diffraction (XRD). The thicknesses and the refractive indices of the SBT layers were calculated with SE using different parametric dielectric function models. The samples were characterized with RBS using different tilt angles and probe ions to enhance the depth resolution and the mass separation. Comparison with SE measurements supports the results of Bahng et al. revealing an increasing refractive index ( n) with increasing Bi/Sr ratio. The decreasing grain size measured by XRD was reflected as a decrease of n in the SE measurement. We show that RBS, XRD, and SE supply a wide range of information about the SBT layers, which can be used for qualification as well as for feedback to layer production. The results suggest that by SE, being used as in situ or in line characterization tool, the control of even complex MOCVD deposition looks feasible.

Numerical modeling of silicon oxide particle formation and transport in a one-dimensional low-pressure chemical vapor deposition reactor

A numerical model is presented for particle formation and transport during low-pressure chemical vapor deposition of silicon dioxide films from silane and oxygen. A detailed chemical kinetics approach was used to model silicon oxide clustering that leads to homogeneous nucleation. A moment-type aerosol dynamics model was developed, which includes particle growth by surface reactions and coagulation, and particle transport by convection, diffusion and thermophoresis, assuming a lognormal particle size distribution function. A chemical clustering mechanism was coupled to the aerosol dynamics model in an axisymmetric stagnation–flow reactor. Simulations were conducted to predict steady-state spatial distributions of major particle characteristics such as particle concentration, diameter and volume fraction. The effects of various system parameters were assessed for conditions around 1.5 Torr (200 Pa) , 800°C, 200 sccm and an inlet oxygen-to-silane ratio of 20. Model predictions are shown to be in good agreement with experimental data and indicate that, unlike the case of particle formation in silane pyrolysis, the results are relatively insensitive to temperature. On the other hand, we observe a large sensitivity to pressure change, which is corroborated by experiment.

Combinatorial Chemical Vapor Deposition of Metal Dioxides Using Anhydrous Metal Nitrates

Modification of a low-pressure CVD reactor and the similar deposition chemistries of Ti(NO3)4, Sn(NO3)4, and Hf(NO3)4 allowed the growth of films on silicon exhibiting a compositional spread of the respective metal dioxides. Electrical measurements of 100 × 100 μm capacitors (shown in the picture) suggest that the dielectric constant of the film can be estimated by a weighted average of the dielectric constants of the individual oxides.

Crack formation due to annealing of Al2O3 films grown on Si(100) by MOCVD

ABSTRACTWe report crack formation in alumina films grown on Si(100), caused by annealing in a controlled oxidizing ambient. The films were grown in a low-pressure CVD reactor, using aluminium acetylacetonate as precursor. High purity argon and nitrous oxide were employed as carrier and oxidizing gas, respectively. The films were characterized by optical microscopy and SEM/EDAX. The proportion and chemical nature of the heteroatoms, namely C and H, incorporated into the films from the precursor, were characterized by XPS, and FTIR. As-deposited films do not exhibit any cracks, while post-deposition annealing results in cracks. Apart from the delamination of the films, annealing in nitrous oxide ambient leads to an unusual crack geometry, which we term the “railway-track”. These twin cracks are very straight and run parallel to each other for as much as several millimeters. Often, two such linear tracks meet at exactly 90°. Between some of these tracks lie bullet-like structures with very sharp tips, oriented in a specific direction. As cracks are generally activated by residual stress, both thermal and intrinsic, the origins of the stresses that generate these linear cracks are discussed. The redistribution of stress, arising from the removal of C and H during annealing, will also be discussed. An attempt has been made to correlate the formation of cracks with the crystal structure of the film.

Visualization and numerical simulation of fine particle transport in a low-pressure parallel plate chemical vapor deposition reactor

The behavior of fine particles in a low-pressure parallel plate chemical vapor deposition reactor was investigated by constructing a system that permits particle motion in the reactor to be visualized. The test spherical silica aerosol particles, which were 1.0 μm in diameter and dispersed in argon gas, were fed into the reactor from the outside and particle motion was detected by a laser light scattering method. The effect of operating conditions, such as pressure and temperature, on particle transport in the reactor was investigated. The pressure was varied from 2.0 to 4.0 Torr and the wafer-substrate plate temperature was varied over the range of 25°C to 300°C. A three-dimensional numerical simulation was performed using the commercially available computational fluid dynamics code Fluent. A detailed configuration of the reactor, including the showerhead structure was considered when investigating this mechanism. It is found, both experimentally and by numerical simulation that, when the wafer-substrate plate is not heated, the effect of pressure on particle trajectory in the space between plates cannot be observed. However, at elevated temperature, i.e. when the wafer-substrate plate is heated, the particle trajectory is apparently influenced by pressure. In addition, the effect of thermophoresis, as the result of a temperature gradient by heating of the wafer-substrate plate is very pronounced for gas pressures of both 2.0 and 4.0 Torr . The experimentally observed phenomena were satisfactorily reproduced by simulation.

Growth of AlN–SiC solid solutions by sequential supply epitaxy

Achieving p-type conductivity in the wide-bandgap semiconductors is still a major research challenge. The AlNSiC alloys have the potential for p- and n-type conductivity based on the properties inherited from the easily-to-dope SiC alloy. However, the growth of high quality AlN–SiC alloys was not achieved yet. In this work we propose a new approach for the growth of AlN–SiC alloys by sequential supply epitaxy (SSE) in a low-pressure metalorganic chemical vapor deposition reactor. The alternated supply of trimethyl aluminum and tetraethyl silane during a first sequence followed by the supply of ammonia and ethylene during a second sequence is used to reduce down to almost eliminating the gas-phase reactions. Also, the SSE technique makes it possible to grow the AlN–SiC solid solutions at temperatures rather low, in the range 1200–1300°C. Solid solutions with a rich content of AlN were investigated. The electron spectroscopy for chemical analysis (ESCA) measurements show that SiC is incorporated in AlN and solid solution is actually achieved. The alloy compositions as revealed by ESCA were in agreement with those estimated from X-ray diffraction. The full width at half maximum of the AlN–SiC diffraction peak is in the range 200–300 s. The surface of the epilayers was mirror-like and had a roughness with a RMS value <5 nm.

Low-Pressure Chemical Vapor Deposition of Semi-insulating Polycrystalline Silicon Thin Films: I. Experimental Study and Proposal of New Kinetic Laws

In the case of the semi-insulating polycrystalline silicon (SIPOS) low-pressure chemical vapor deposition (LPCVD) process, the influence of the two most important operating parameters, gas inlet composition and process temperature, on the evolutions of the deposition rate and of the film oxygen content along the reactor load and on-wafer, has been experimentally studied. This set of experimental results was then used as a database to develop a new kinetic model, using a local numerical simulation code for LPCVD reactors, named CVD2. This new kinetic model certainly summarizes numerous poorly known gas phase and surface reactions involved in SIPOS deposition. Its validation has been successfully performed by comparison with specific experimental data, both along the load and on-wafer. An efficient mathematical tool is then available to better control and optimize the performances of SIPOS low-pressure deposition processes. © 2001 The Electrochemical Society. All rights reserved.

Chemical Vapor Deposition (CVD) of Tungsten Nitride for Copper Diffusion Barriers

ABSTRACTA new process was developed for deposition of the tungsten nitride at moderate substrate temperatures (350-400 °C). The tungsten source bis (tert-butylamido)bis(tertbutylimido) tungsten, (tBuNH)2(tBuN)2W, reacts with ammonia in a low-pressure CVD reactor. Growth rates ranged from about 0.6 to 4.1 nm per minute. The stoichiometry of the films varied from WN1.2O1.7 to WN1.6o0.25, depending mainly on deposition temperature. The films are amorphous by X-ray diffraction, and smooth by scanning electron microscopy. Step coverage is nearly 100% in vias with an aspect ratio of 6:1 for films deposited at 400 °C or lower. Barriers 45 nm thick resist diffusion of copper up to temperatures of 600 °C. Adhesion is strong to all substrates tested, including silicon, silicon dioxide, soda-lime glass, glassy carbon, aluminum and stainless steel. This new halogen-free process avoids halogen contamination of films and corrosion of equipment. Uniformity of thickness and stoichiometry are readily achieved. This process is a promising method for forming copper diffusion barriers in future generations of microelectronics.

Effect of oxygen pressure upon composition variation during chemical vapor deposition growth of lead titanate films from tetraethyl lead and titanium tetraisopropoxide

Lead titanate (PbTiO 3) films have been prepared from mixtures of tetraethyl lead (Pb(C 2H 5) 4), titanium tetrasiopropoxide (Ti(i-OC 3H 7) 4) and oxygen (O 2) by a low-pressure chemical vapor deposition (LPCVD) reactor. The effects of O 2 to the film growth including growth rate, crystalline property, and composition are investigated. Without adding O 2, the film formed at 823 K shows only TiO 2 XRD diffraction pattern, whereas stoichiometric PbTiO 3 is formed after adding 1 vol.% of O 2. Based on RBS composition analyses, increasing surplus O 2 concentration not only decreases the amount ratio of Pb but also causes concentration profile of Pb in the films. The deviation of Pb composition is reduced by raising the substrate temperature up to 873 K. A thermodynamic calculation of the stability domain of the Pb–O system suggests that the formation of high valence lead oxides having high volatility during film deposition is responsible for the Pb-deficient phenomenon in this CVD process.

Synthesis of Pyrite (FeS2) Thin Films by Low-Pressure MOCVD

Thin films of iron disulfide have been prepared by low-pressure CVD (LPCVD) from iron(III) acetylacetonate (Fe(acac) 3 ), tert-butyldisulfide (TBDS), and hydrogen. The influence of the relevant CVD parameters on the growth rate, chemical composition (stoichiometry), morphology, crystalline phases, and contaminants has been examined. Pyrite thin films with a uniformity variation of less than 5 % over a length of 10 cm are obtained in a hot-wall LPCVD reactor. The present study shows that these films are deposited without detectable iron sulfide (FeS) phases at temperatures from 300 °C up to 340 °C on glass and silicon substrates. Growth rates vary between 0.2 nm min -1 and 12 nm min -1 . In all cases, the films are polycrystalline pyrite with an indirect bandgap of 0.95 ± 0.05 eV, and a dark specific resistance of 0.5-1.0 Ω cm. The absorption coefficient of the films is 3 ± 1 × 10 5 cm -1 at λ = 500 nm.

Low temperature Si epitaxy in a vertical LPCVD batch reactor

Silicon epitaxy on wafers is becoming more and more important for substrates in CMOS mass production, and has traditionally been used for bipolar and BiCMOS devices. This paper presents a new process solution in a vertical low-pressure chemical vapor deposition reactor allowing low cost batch processing for deposition of thin Silicon epitaxial layers at temperatures not exceeding 800°C. In situ cleaning of wafers in the reactor prior to the SiH 4 deposition process shows significant influence on the quality of epitaxial layers. The problem of deposition on hot reactor walls has been solved by integration of remote plasma enhanced dry etching. We will present test results demonstrating the capabilities of the epitaxy process in this new tool. Finally, cost of ownership calculations will be presented showing the economic attraction of this new solution in comparison with single-wafer high temperature techniques.

Study of the growth mechanisms of low-pressure chemically vapour deposited silica films

We have studied the surface morphology evolution of SiO 2 films grown at 20 nm/min in a low-pressure chemical vapour deposition reactor from SiH 4 /O 2 mixtures at low (611 K) and high (723 K) temperatures. Films have been deposited for times ranging from 10 min up to 48 hours. It is shown that the SiO 2 growth at high temperature becomes stable, whereas at low temperature it is unstable (i.e., the surface roughness increases continuously with deposition time). This clear difference is explained on the basis of the different growth mechanisms operating under both experimental conditions. These results are compared with the predictions of the few theoretical works on growth evolution by chemical vapour deposition.

MOCVD of ferroelectric thin films

Ferroelectric thin films of lead titanate (PbTiO 3 ) and lead zirconate titanate (PZT) were grown in a cold-wall low-pressure chemical vapor deposition reactor on silicon substrates with diameters up to 150mm using liquid metal organic precursors including a novel zirconium precursor. Film thickness ranged from 10nm to 700nm. The films were characterized regarding their electrical, optical, and structural properties depending on film composition and deposition conditions. In this paper, we report our results regarding composition effects, the electrical polarization behavior and optical properties like refractive indices and absorption coefficient, which were investigated by spectroscopic ellipsometry for a wide wavelength range. Furthermore some temperature dependent effects of the platinum electrodes are described.

Phase controlled low-pressure chemical vapor deposition of iron(di)sulfide

Thin films of iron(di)sulfide pyrite, marcasite, and pyrrhotite have been prepared on glass substrates by low-pressure chemical vapor deposition (LPCVD) from iron(III)acetylacetonate (Fe(acac) 3 ) and tert-butyl disulfide (TBDS), using a cold-wall LPCVD reactor. It is found that the temperature determines the crystalline phases of the films. Deposition temperatures of 350 and 375°C yield pure polycrystalline pyrite with an indirect and a direct band gap of 0.95 and 1.45 eV, respectively. By increasing the temperature up to 425°C, a mixture of pyrite, marcasite, and pyrrothite is formed, while between 425 and 450 °C mixtures of pyrite and pyrrhotite are obtained Temperatures of 480 °C cause the formation of pyrrothite films.

Synthesis of pyrite (FeS2) thin films by low pressure metal-organic chemical vapor deposition

Thin films of iron disulfide have been prepared by Low-Pressure Chemical Vapor Deposition (LPCVD) from iron(III)acetylacetonate (Fe(acac) 3 ). lert-butyl disulfide (TBDS), and hydrogen. The influence of the relevant CVD parameters on the growth rate, chemical composition (stoichiometry), morphology, crystalline phases, and contaminants have been examined. Pyrite thin films with a uniformity variation of less than 5% over a length of 10 centimeters are obtained in a hot wall LPCVD reactor. We are able to deposit these films without detectable iron sulfide (FeS) phases at temperatures from 300 °C up to 340 °C on glass, titanium dioxide, and silicon. Growth rates vary between 0.2 and 12 nm/min. In all cases, the films are polycrystalline pyrite with an indirect band gap of 0.95 ± 0.05 eV, a direct band gap between 1.4 and 1.5 eV, and a dark specific resistance of 0,5 - 1.0 Ωcm. The absorption coefficient of the films is 3 ± 1 x 10 5 cm -1 at λ = 500 nm. The Seebeck coefficient is between 30 and 70 μVK -1 and is always positive which indicates p-type conductivity.