Rotating Disk Chemical Vapor Deposition Research Articles

Flow field investigation in a rotating disk chemical vapor deposition chamber with a perforated showerhead

A flow field in a simulated rotating disk chemical vapor deposition chamber in which the inflow gases entered through a showerhead inlet was experimentally investigated using particle image velocimetry. The deposition uniformity was highly related to the flow pattern, which was influenced by the buoyancy, centrifugal, and flow inertia forces. This study investigated flow patterns for different processing parameters, namely chamber heights (20 and 40mm), jet-to-disk temperature differences (0–500°C), and disk rotational speeds (0–500rpm). The time-averaged axial and radial velocity profiles were determined for examining the effects of rotation and heating on flow uniformity above the rotating disk. The Reynolds stress and turbulence intensity was found to be influenced by the buoyancy and rotation induced flow. At a high jet-to-disk temperature difference, the upward buoyancy force lifted the flow and prevented the inlet flow from reaching the disk surface. The buoyancy-induced flow can be suppressed through disk rotation or chamber height reduction. Moreover, the nondimensional parameters (Grashof number and rotational Reynolds number) can be used to construct flow regime maps and quantify the effects of rotation and heating even with the contribution from different chamber heights, disk temperatures, and rotational speeds.

Epitaxial growth of silicon nanowire arrays at wafer-scale using high-speed rotating-disk CVD for improved light-trapping

Silicon nanowires (Si-NWs) have been fabricated at wafer-scale with Au nanoparticles as catalysts at 500 °C using a chemical-vapor-deposition (CVD) method combined with a high-speed rotation wafer-disk. High resolution TEM and SAED patterns were used to characterize the microstructures of the grown Si-NWs. Single crystalline Si-NWs appear self-oriented on Si (100) substrates along the growth axis. The nanowires have a uniform diameter of 50 nm and varying lengths and densities depending on the rotation speed of the wafer substrate. The effects of wafer-rotation speed on the growth of Si-NWs are discussed. Due to a reduced boundary layer thickness, fast mass transport leads to both an enhanced growth rate and density of the Si-NWs. Moreover, the density of the Si-NW array is optimized to achieve a low reflectance loss for their further application in tandem solar cells as the light-trapping layer.

3D CFD for chemical transport profiles in a rotating disk CVD reactor

The RDCVD (Rotating Disk Chemical Vapor Deposition) technique is an appropriate method for uniform deposition of grains, such as compound semiconductior materials. The substrate temperature and rotation speed are the major factors, which determine the thickness uniformity of the deposited films. This paper investigates 3D CFD (3 Dimensional Computational Fluid Dynamics) simulation results of flow and heat transfer in a reactor of RDCVD using Fluent. In order to establish the reducibility of buoyancy effect on deposition quality, the chemical transport profile upon the disk heated is examined successfully in 3D domain for different rotating speeds. The resulting vortex flows due the simultaneous buoyance and centrifuge are discussed qualitatively in the 3D virtual system of a RDCVD reactor. 3D CFD is even more effective to describe the internal vortex flows due to the competitive inlet, buoyancy and centrifuge flows, which cannot be realized in the general 2D (2 Dimensional) CFD.

Newly Developed High-Speed Rotating Disk Chemical Vapor Deposition Equipment for Poly-Si Films

We have developed high-speed rotating disk chemical vapor deposition (CVD) equipment. A high deposition rate, good thickness uniformity and few particles were achieved for polycrystalline silicon (poly-Si) film deposition on a 200-mm-diameter silicon (Si) wafer, by optimizing the structure of the rotating disk CVD equipment. A magnetic bearing motor was used for rotating and controlling the 200-mm-diameter wafer at 3000 rpm, and the substrate temperature was controlled to be 600–900°C. Gas flow was also controlled to avoid the re-adsorption of reaction by-products onto the wafer surface. A deposition rate of 316 nm/min, a film thickness nonuniformity ±3%, and less than 20 particles (over 200 nm in diameter) were achieved at a deposition temperature of 680°C for poly-Si deposition on the 200-mm-diameter wafer. These results show that the number of particles can be reduced even at a high deposition rate. The mechanisms of the high performance for poly-Si deposition are considered to be the reduction in the thickness of the boundary layer of temperature above the wafer surface and the suppression of the vapor-phase reaction.

A numerical investigation of the effects of gas-phase particle formation on silicon film deposition from silane

This paper presents a systematic numerical investigation of the effects of particle formation on silicon film deposition from silane in a vertical rotating disk chemical vapor deposition reactor. The numerical model uses the Sandia SPIN code to simulate the reacting flow and heat transfer. A moment transport aerosol model simulates the nucleation, growth and transport of silicon particles. The effects of total reactor pressure, temperature, rotation rate, inlet gas composition, and rate of particle growth via condensation on the deposition rate of the silicon film are investigated. Results are presented detailing the scavenging of film growth precursor molecules by particles through a series of simulations both with and without an aerosol component. Conditions under which the particles affect the deposition rate have been identified. Additionally, the use of a chemically reactive carrier (H 2) is shown to effectively suppress the formation of particles in the gas phase. The effect of this particle suppression on the deposition rate is discussed.

Mixed binary convection in a rotating disk chemical vapor deposition reactor

This study examines the effects of gas mixing on flow behavior in a rotating disk reactor. We restrict the study to an isothermal binary gas system flowing over a high speed rotating disk in a cylindrical reactor. Complex flow fields are produced as a result of the interaction that occur between the solutal buoyant force, the forced flow, and the flow induced by the rotation of the disk. Deviation from the ideal rotating disk flow is quantified with a radial shear stress parameter.

Laser-Induced Fluorescence Measurements and Kinetic Analysis of Si Atom Formation in a Rotating Disk Chemical Vapor Deposition Reactor

An extensive set of laser-induced fluorescence (LIF) measurements of Si atoms during the chemical vapor deposition (CVD) of silicon from silane and disilane in a research rotating disk reactor are presented. The experimental results are compared in detail with predictions from a numerical model of CVD from silane and disilane that treats the fluid flow coupled to gas-phase and gas-surface chemistry. The comparisons showed that the unimolecular decomposition of SiH[sub 2] could not account for the observed gas-phase Si atom density profiles. The H[sub 3]SiSiH [leftrightarrow] Si + SiH[sub 4] and H[sub 3]SiSiH + SiH[sub 2] [leftrightarrow] Si + Si[sub 2]H[sub 6] reactions are proposed as the primary Si atom production routes. The model is in good agreement with the measured shapes of the Si atom profiles and the trends in Si atom density with susceptor temperature, pressure, and reactant gas mixture. 33 refs., 12 figs., 3 tabs.

Design and Verification of Nearly Ideal Flow and Heat Transfer in a Rotating Disk Chemical Vapor Deposition Reactor

A research chemical vapor deposition reactor design is presented for a rotating disk configuration. The reactor can be operated under conditions such that nearly ideal, one‐dimensional, infinite‐radius disk behavior is achieved over most of the disk surface. Boundary conditions, flow stability under both isothermal and heated‐disk conditions, and gas temperatures are addressed with both one‐ and two‐dimensional numerical fluid mechanics models. Experimental verification of the design using flow visualization and laser Raman thermometry are presented.

A Mathematical Model of the Fluid Mechanics and Gas‐Phase Chemistry in a Rotating Disk Chemical Vapor Deposition Reactor

We describe a mathematical model of the coupled fluid mechanics and gas‐phase chemical kinetics in a rotating disk chemical vapor deposition reactor. The analysis is for the flow between an infinite radius, heated nonporous rotating disk and a parallel infinite radius porous surface through which reactive fluid is injected normal to the disk. The analysis extends the usual von Karman transformation to allow specification of the normal velocity at the porous disk, and reduces to a stagnation point flow in the limit of zero rotating rate. The deposition of silicon from silane is used as an example system. A new reaction mechanism and set of rate constants are given for the thermal decomposition of silane. We present an RRKM analysis of several of the unimolecular reactions in the mechanism. Calculated velocity and temperature profiles, chemical species density profiles, and deposition rates as functions of susceptor temperature, spin rate, and inlet flow velocity are presented.

A Numerical Model of the Flow and Heat Transfer in a Rotating Disk Chemical Vapor Deposition Reactor

Steady, laminar, axisymmetric, and circumferentially uniform flow and heat transfer, including the effects of variable properties and buoyancy, have been modeled within a rotating disk chemical vapor deposition (CVD) reactor. The reactor is oriented vertically, with the hot, isothermal, spinning disk facing upward. The Navier–Stokes and energy equations have been solved for the carrier gas helium. The solutions have been obtained over a range of parameters, which is of importance in CVD applications. The primary parameters are the ratio of the disk temperature to the free stream temperature Tw/T∞, the disk Reynolds number Re = rd2ω/ν∞, a mixed convection parameter Gr/Re3/2 = g(ρ∞ − ρw)/(ρwωων∞), the dimensionless inlet velocity u∞/ων∞, and two geometric parameters ro/rd and L/rd. Results are obtained for the velocity and the temperature fields and for the heat flux at the surface of the rotating disk. Comparisons are made with the one-dimensional, variable-property (excluding buoyant effects), infinite rotating disk solutions of Pollard and Newman. Results are presented in terms of a local Nusselt number. The potential uniformity of CVD in this geometry can be inferred from the variation of the Nusselt number over the surface of the rotating disk. The effects of buoyancy and the finite size of the rotating disk within the cylindrical reactor are clearly evident in the present work.

Effects of Boundary Conditions on the Flow and Heat Transfer in a Rotating Disk Chemical Vapor Deposition Reactor

Effects of Boundary Conditions on the Flow and Heat Transfer in a Rotating Disk Chemical Vapor Deposition Reactor