Low-pressure Chemical Vapor Deposition Reactor Research Articles

Design and Performance of an LPCVD Reactor for the Growth of 3C-Silicon Carbide

This paper discusses the design of a low pressure chemical vapor deposition (LPCVD) reactor and growth of β silicon carbide (3C-SiC) thin films on Si. The reactor’s hot-zone configuration radiatively couples the graphite heater (no physical contact) to Si substrates with realized temperatures . We implemented a four-stage growth procedure using silane and propane precursors and hydrogen as the carrier gas. Temperatures, pressures, and flows varied from , from , and from during growth, respectively. Growth of 3C-SiC was confirmed using X-ray diffraction (XRD) with the observation of a (200) peak located at 41.4°. Activation energies of 21.5 and were calculated for the kinetically and mass-transport-limited regimes for polycrystalline 3C-SiC growth. The polycrystalline 3C-SiC films with fewest defects and smallest XRD full width at half-maximum were deposited at with a growth rate of using flow rates of , , and of (conc. 1.16%). The composition of the films measured by X-ray photoelectron spectroscopy shows that the films are slightly carbon rich with oxygen as the main source of contamination. Voids were observed at the film–substrate interface for samples grown at high precursor concentrations.

Electrical and Mechanical Characterization of Doped and Annealed Polycrystalline 3C-SiC Thin Films

+Deposition of doped polycrystalline 3C-SiC thin films from the precursors 1,3-disilabutane (DSB) and dichlorosilane (DCS), and the dopant precursor ammonia is investigated in a large-scale low-pressure chemical vapor deposition (LPCVD) reactor for micro- and nanoelectromechanical systems (M/NEMS) applications. Films deposited from only DSB and have residual stresses in excess of tensile and resistivity values of . Addition of DCS yields films that exhibit mechanical and electrical properties more favorable for M/NEMS devices. For films deposited with DCS, electrical resistivity varies between for undoped, as-deposited films to for films doped with nitrogen. Residual stress of films deposited from DSB, DCS, and varies little for as-deposited films with different doping concentrations; however, annealing in an argon ambient shifts residual stress toward, and in some cases, into the compressive regime. The strain gradient, which is less than in magnitude for all as-deposited films from DSB, DCS, and , shifts to large negative values in excess of upon annealing for at in an argon ambient. Two sources of stress shift with annealing are identified, namely oxygen diffusion and a change in N atom bonding.

Low-Pressure Metallorganic Chemical Vapor Deposition of Fe2O3 Thin Films on Si(100) Using n-Butylferrocene and Oxygen

thin films have been deposited on Si(100) substrates using n-butylferrocene and oxygen in a low-pressure metallorganic chemical vapor deposition reactor. The iron precursor is liquid at room temperature having a high enough vapor pressure; its thermogravimetric analysis shows that it undergoes clean evaporation without decomposition. The growth rates were studied in the temperature range of . The resulting thin films were characterized for structure and morphology using X-ray diffraction and scanning electron microscopy. Their composition was analyzed using energy-dispersive X-ray spectroscopy, and chemical bonding states were probed using X-ray photoelectron spectroscopy. Films deposited at were mostly noncrystalline and had carbon contamination. Films deposited at higher temperatures were crystalline .

LP-MOCVD growth of ternary BxGa1−xAs epilayers on (0 0 1)GaAs substrates using TEB, TMGa and AsH3

Zinc-blende BxGa1−xAs alloys have been successfully grown on exactly oriented (001)GaAs substrates using triethylboron, trimethylgallium and arsine sources. The growth has been accomplished in a vertical low-pressure metalorganic chemical vapor deposition (LP-MOCVD) reactor. Boron incorporation behaviors have been extensively studied as a function of growth temperature and gas-phase boron mole fraction. The evolution of surface morphology was also observed.The maximum boron composition of 5.8% is obtained at the optimum growth temperature of 580°C. RMS roughness over the surface area of 1×1μm2 is only 0.17nm at such growth conditions. Based on the experimental results, it has been clearly shown that boron incorporation will decrease significantly at higher temperature (>610°C) or at much lower temperature (⩽550°C).

Nickel and platinum ohmic contacts to polycrystalline 3C-silicon carbide

Nickel and platinum contacts to n-type doped polycrystalline 3C-SiC (poly-3C-SiC) were characterized by the circular transmission line method (CTLM) at room temperature and 300 °C. The poly-3C-SiC films were deposited at 800 °C using 1,3-disilabutane single precursor in a low-pressure chemical vapor deposition (LPCVD) reactor, and were in situ nitrogen doped using NH 3. Nickel contacts to poly-3C-SiC showed ohmic characteristics at room temperature, with contact resistivity varying with the doping content of poly-3C-SiC films and reaching the minimum value of 1.6 × 10 −6 Ω cm 2. The contact resistivity increased to 1.3 × 10 −5 Ω cm 2 after the contact was annealed at 300 °C in air. Platinum contact to poly-3C-SiC was also ohmic with an as-deposited contact resistivity of 1.2 × 10 −5 Ω cm 2, but better thermal stability. A stable ohmic contact at 300 °C was achieved with a contact resistivity of about 3.6 × 10 −5 Ω cm 2 on Pt contacts to poly-3C-SiC films.

Chemical vapor deposition of NiSi using Ni(PF 3) 4 and Si 3H 8

NiSi x films were deposited using chemical vapor deposition (CVD) with a Ni(PF 3) 4 and Si 3H 8/H 2 gas system. The step coverage quality of deposited NiSi x was investigated using a horizontal type of hot-wall low pressure CVD reactor, which maintained a constant temperature throughout the deposition area. The step coverage quality improved as a function of the position of the gas flow direction, where PF 3 gas from decomposition of Ni(PF 3) 4 increased. By injecting PF 3 gas into the Ni(PF 3) 4 and Si 3H 8/H 2 gas system, the step coverage quality markedly improved. This improvement in step coverage quality naturally occurred when PF 3 gas was present, indicating a strong relationship. The Si/Ni deposit ratio at 250 °C is larger than at 180 °C. It caused a decreasing relative deposition rate of Ni to Si. PF 3 molecules appear to be adsorbed on the surface of the deposited film and interfere with faster deposition of active Ni deposition species.

Deposition Uniformity Control in a Commercial Scale HTO-CVD Reactor

AbstractHigh-temperature silicon dioxide chemical vapor deposition (HTOCVD), using SiH2Cl2 and N2O, can realize dense and conformal oxide film, not only on large size silicon wafers, but even inside of microscopic silicon trenches, at high-temperature around 800°C.In this work, we investigated the kinetics of HTOCVD using a commercial scale low pressure (LP) CVD reactor, focusing on the correlation between deposition rate and surface-to-volume ratio (S/V ratio), which is a specific surface area of substrate wafer divided by the space volume between two adjacent wafers. We also investigated the deposition rate profile on wafers, and along the axial direction of the reactor near the region where one, two or three substrate wafers are extracted from the quartz holder. The deposition rate profiles on wafer characteristically change from skillet-like to pancake-like, according to the increase of wafer spacing. The influence on the deposition rate of wafer spacing spreads to ranges not only downstream, but also upstream in the gas flow. These experimental results strongly suggest that in the HTOCVD gas-phase reactions through intermediate states of active species contribute to deposition reaction as well as direct deposition reaction of source gases on Si surface.

Growth of 3C-SiC on Si Molds for MEMS Applications

A hetero-epitaxial 3C-SiC growth process in a low-pressure hot-wall CVD reactor has been developed on planar Si (100) substrates. The growth rate achieved for this process was about 10 μm/h. The process consists of silane/propane/hydrogen chemistry with HCl used as a growth additive to increase the growth rate. 3C-SiC has also been grown on 22, 52 and 123 +m deep etched MEMS structures formed by DRIE of (100) Si at a rate of about 8 +m/h. Secondary electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) were used to analyze the quality of the 3C-SiC films.

Ion Implanted p<sup>+</sup>/n Diodes: Post-Implantation Annealing in a Silane Ambient in a Cold-Wall Low-Pressure CVD Reactor

This work reports the realization and characterization of 4H-SiC p+/n diodes with the p+ anodes made by Al+ ion implantation at 400°C and post-implantation annealing in silane ambient in a cold-wall low-pressure CVD reactor. The Al depth profile was almost box shaped with a height of 6×1019 cm-3 and a depth of 160 nm. Implant anneals were performed in the temperature range from 1600°C to 1700°C. As the annealing temperature was increased, the silane flow rate was also increased. This annealing process yields a smooth surface with a roughness of the implanted area of 1.7 - 5.3 nm with increasing annealing temperature. The resistivity of the implanted layer, measured at room temperature, decreased for increasing annealing temperatures with a minimum value of 1.4 0-cm measured for the sample annealed at 1700°C. Considering only the current-voltage characteristic of a diode that could be modeled as an abrupt p/n junction within the frame of the Shockley theory, the diode process yield and the diode leakage current decreased, respectively, from 93% to 47% and from 2×10-7 Acm-2 to 1×10-8 Acm-2 at 100 V reverse bias, for increasing post implantation annealing temperature.

Single-Source Chemical Vapor Deposition of SiC Films in a Large-Scale Low-Pressure CVD Growth, Chemical, and Mechanical Characterization Reactor

The development and characterization of a silicon carbide deposition process from a single source precursor, 1,3-disilabutane, in a large-scale reactor is described. Deposition was performed simultaneously on fifteen, Si wafers in a 4 or wafer-capable horizontal low-pressure chemical vapor deposition reactor. Amorphous is obtained at temperatures of and below, while some polycrystallinity is obtained at temperatures of and above. Highly uniform and relatively smooth films are realized using a closed wafer boat. A maximum growth rate of is attained at . Residual stress in the film is characterized and found to be greater than (tensile) across a wide range of deposition temperatures. Stress profiling is performed to investigate the stress distribution throughout the films. Microfabrication on the wafer level using as a structural layer is also demonstrated.

Morphological study of polycrystalline SiGe alloy deposited by vertical LPCVD

As device dimensions shrink to the deep-submicron scale, new challenges arises from the very small scale used and even poly crystalline silicon (poly-Si) presents problems as gate electrode. The use of SiGe as gate material can present many advantages over the poly-Si, as it leads to a lower boron penetration and gate depletion. In this paper authors present some morphological studies of polycrystalline SiGe thin films deposited in a vertical LPCVD (Low Pressure Chemical Vapor Deposition) reactor for using as MOS (Metal Oxide Semiconductor) gate electrode.

Modeling of Silicon Nanodots Nucleation and Growth Deposited by LPCVD on SiO2 : From Molecule/surface Interactions to Reactor Scale Simulations

ABSTRACTWe present first results combining models at continuum and atomistic (DFT) levels to improve understanding of key mechanisms involved in silicon nanodots (NDs) synthesis on SiO2 by Low Pressure Chemical Vapor Deposition (LPCVD) from silane SiH4. In particular, by simulating an industrial LPCVD reactor using the CFD code Fluent, we find that the deposition time could be increased and then the reproducibility and uniformity of NDs deposition could be improved when highly diluting silane in a carrier gas. A consequence of this high dilution seems to be that the contribution to deposition of unsaturated species such as silylene SiH2 highly increases. This result is important since our first DFT calculations have shown that silicon chemisorption on silanol Si-OH or siloxane Si-O-Si bonds present on SiO2 substrates could only proceed from silylene (and probably from other unsaturated species). The silane saturated molecule could only contribute to NDs growth, i.e. silicon chemisorption on already deposited silicon bonds. Increasing silylene contribution to deposition in highly diluting silane could then also exalt silicon nucleation on SiO2 substrates and then increase NDs density.

MOCVD deposition of CoAl 2O 4 films

Cobalt aluminate (CoAl 2O 4) thin films were grown in a low-pressure hot wall metal organic chemical vapour deposition (MOCVD) reactor on Si(1 0 0) and quartz substrates with a total pressure of 2 Torr using bis(η 5-cyclopentadienyl)Co(II) [Co(η 5-C 5H 5) 2] and aluminium dimethylisopropoxide [AlMe 2(O i Pr)] as precursors at 500 and 900 °C. Films showed a dark-brown and dark-green colouration, respectively, and after an overnight heat treatment in air at 1200 °C, they turned blue. Film microstructure, composition and morphology were investigated in detail by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) analyses. Films were polycrystalline and the UV–vis spectra showed three electronic transitions allowed by the spin (540–630 nm range) characteristic of Co(II) ions with 3d 7 configuration in tetrahedral coordination. SEM micrographs of the heat-treated CoAl 2O 4 samples revealed the presence of agglomerated crystallites with a highly porous structure.

Visualization and Numerical Simulation of Rarefied Gas Flow in Vertical Low-Pressure CVD Reactors for Thin Film Formation of Semiconductors

The paper investigates the flow characteristics of reactant gas on the silicon wafers in a vertical LPCVD (Low-Pressure Chemical Vapor Deposition) reactor by the flow visualization and the numerical simulation. The observation was made in a model reactor in a very low-pressure condition, which makes the observation quite difficult because of tracer seeding. The CFD code FLUENT was used for the numerical simulation. The results of the visualization and the numerical simulation showed that the gas flow was quite viscous and it received large resistance force from the wafers and the supporting lodes. Regardless of the low-pressure condition, the flow can be treated as continuous system and can be simulated well by the CFD code based on Navier-Stokes equation. It shows that the most of the field appeared to be laminar. For the establishment of the uniform flow pattern, twin counter-flow nozzles were better than a single nozzle. The flow was free from stagnant flow or re-circulating flow so that it appeared to be suited for the prevention of particle formations.

Modelling of transport phenomena in a low-pressure CVD reactor

The present work reports the analysis of transport phenomena in a low-pressure chemical vapour deposition (CVD) reactor. A two-dimensional unsteady model has been used to compute flow, chemical reactions and mass transfer rates within the reactor. The formation of zinc sulphide from the reaction of zinc vapour and gaseous hydrogen sulphide has been analysed. Two geometric designs of the reactor have been studied for assessing the overall deposition characteristics. The mathematical model comprises of the conservation equations of mass, momentum and the mass fractions of the reactant and product species. The governing partial differential equations have been solved by the finite volume method. The deposition surface has been taken to be chemically passive. There is an uncertainty in the boundary condition for the depositing species on the passive surface. The difficulty has been resolved by utilizing a homogenous Dirichlet condition at the surface. The present approach yields an upper bound on the deposition rate. The numerical results obtained show that the species concentration field, correlates closely to the flow field in the reactor. Over the range of Reynolds numbers studied namely 10–200, a recirculation pattern adjacent to the side walls is revealed and a stagnation zone forms ahead of the block. Reactant species mix predominantly in the zone close to the inflow plane and the product species are transported by advection. The reactor with a convex substrate streamlines the flow better as compared to the concave. As a result, higher concentrations of the product species reach the substrate. At a Reynolds number of 100, the deposition rate for the convex substrate was seen to increase by a factor of two with respect to the concave.

Modelling of transport phenomena in a low-pressure CVD reactor

The present work reports the analysis of transport phenomena in a low-pressure chemical vapour deposition (CVD) reactor. A two-dimensional unsteady model has been used to compute flow, chemical reactions and mass transfer rates within the reactor. The formation of zinc sulphide from the reaction of zinc vapour and gaseous hydrogen sulphide has been analysed. Two geometric designs of the reactor have been studied for assessing the overall deposition characteristics. The mathematical model comprises of the conservation equations of mass, momentum and the mass fractions of the reactant and product species. The governing partial differential equations have been solved by the finite volume method. The deposition surface has been taken to be chemically passive. There is an uncertainty in the boundary condition for the depositing species on the passive surface. The difficulty has been resolved by utilizing a homogenous Dirichlet condition at the surface. The present approach yields an upper bound on the deposition rate. The numerical results obtained show that the species concentration field, correlates closely to the flow field in the reactor. Over the range of Reynolds numbers studied namely 10–200, a recirculation pattern adjacent to the side walls is revealed and a stagnation zone forms ahead of the block. Reactant species mix predominantly in the zone close to the inflow plane and the product species are transported by advection. The reactor with a convex substrate streamlines the flow better as compared to the concave. As a result, higher concentrations of the product species reach the substrate. At a Reynolds number of 100, the deposition rate for the convex substrate was seen to increase by a factor of two with respect to the concave.

Nanolaminates of Zirconia and Silica Using Atomic Layer Deposition

In a low-pressure chemical vapor deposition reactor, alternating exposure of Si(100) substrates to tri(tert-butoxy) silanol and anhydrous zirconium nitrate deposited mixed films of zirconia and silica at 162 °C. The deposition rate, defined as the thickness (Å) per cycle, exhibited saturation behavior indicative of self-limiting growth. The maximum rate of approximately 12 Å/cycle exceeded the thickness expected for a single monolayer each of ZrO2 and SiO2. Metal composition of the films, as determined using Rutherford backscattering spectrometry, ranged from 3.3 to 49% zirconium. A singular reflection in the low-angle X-ray scattering pattern had a d spacing indicative of an ordered bilayer structure. The films were atomically smooth and their thickness was uniform across the entire substrate. Both the refractive indices, measured by ellipsometry, and the effective dielectric constants exhibited a linear dependence on the zirconium concentration.

Single-Source CVD of 3 C ­ SiC Films in a LPCVD Reactor: II. Reactor Modeling and Chemical Kinetics

The deposition of 3C-SiC films on Si(100) wafers from 1,3-disilabutane precursor (1,3-DSB) molecule utilizing a conventional low pressure chemical vapor deposition (LPCVD) system is studied theoretically. The LPCVD reactor is modeled as a 1D system with axial dispersion. The reaction path of the 1,3-DSB decomposition is studied through quantum chemical methods due to the lack of kinetic information on this molecule. First, the transition state for the decomposition reaction is calculated, then the fall-off regime of the reaction is determined using the Rice-Ramsperger-Kassel-Marcus theory. The surface kinetics is taken-mainly from literature data. The kinetic scheme obtained in this manner is first embedded into a 0D model to evaluate the most important kinetic processes, then a simplified kinetics is adopted in the 1D model. Finally, the calculated growth rates are compared with experimental data taken at different temperatures. The agreement between calculated and experimental data shows the importance of the gas-phase decomposition reactions during the SiC deposition even in a low-pressure process. © 2004 The Electrochemical Society. All rights reserved.

Combinatorial CVD of ZrO2 or HfO2 compositional spreads with SiO2 for high ? dielectrics

A modified low-pressure chemical vapor deposition reactor was used to create compositional spreads of MO2/SiO2 films (M = Hf or Zr) on a single Si(100) wafer. Tri(tert-butoxy)silanol and anhydrous metal nitrates of hafnium and zirconium were used to grow films at temperatures as low as 130 °C. The films were characterized by ellipsometry and Rutherford backscattering spectrometry. The compositional spreads of 5–54% of Hf in the HfO2/SiO2 system and 5–62% of Zr in the ZrO2/SiO2 system are proposed to result from chemistry occurring between the two precursors. A survey of possible reactions involved in the deposition is included. The dielectric constant ranged from approximately 4 in the silica-rich locations to 17 in the ZrO2-rich and HfO2-rich locations.

Improved size dispersion of silicon nanocrystals grown in a batch LPCVD reactor

ABSTRACTNanocrystal memories are widely invoked as potential solutions to overcome the scaling limitations of conventional FLASH memories beyond the 80nm technology node. In this study, the deposition of uniform silicon nanocrystals has been developed and optimized in a commercially available vertical furnace, an A400 from ASM.It has been shown that low pressure chemical vapor deposition (LPCVD) of nanocrystals is feasible in a batch reactor but with a bad size dispersion of the silicon nanocrystals. To improve the size dispersion of the nanocrystals, a novel 2-step process with silane was introduced. In the conventional 1-step process, the oxide surface is exposed to silane at the same partial pressure and temperature during both nucleation and growth of the silicon nanocrystals. In this novel 2-step process, the surface is first exposed briefly to silane at a higher temperature (580–600°C) and following that, the temperature is lowered to allow selective growth on the existing silicon nuclei over the oxide surface. With such an approach, the nucleation step can be separated from the growth step and consequently the size dispersion can be improved by 50%.