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Hot-Wire Chemical Vapor Deposition (HWCVD) technologies

Rapid, controllable growth of epitaxial silicon films

National Renewable Energy Laboratory

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Technology Marketing Summary

NREL scientists have discovered a unique way to quickly grow epitaxial Si using hot-wire chemical vapor deposition (HWCVD), which holds the potential to greatly decrease costs within the manufacturing of Si substrates.  With NREL’s HWCVD technology, Si material use and costs are dramatically reduced with scalable manufacturing and lower deposition temperatures.  NREL’s unique HWCVD technique can easily be integrated into existing manufacturing processes, allowing quick implementation.  Rapid and controllable growth ensures a fast deposition rate and accurate thickness, thus allowing NREL’s technology to be cost competitive, even with the dramatic drop in conventional c-Si PV cells.


The solar market has changed dramatically over the last three years as an influx of low cost silicon (Si) has entered the market. In order to gain a competitive edge, manufacturers are now looking to decrease the amount of materials used in solar photovoltaic (PV) cells.  While traditionally this effort has concentrated only a few thin-film manufacturing materials and techniques, the drop in Si prices has forced for the development of innovations in deposition and advanced manufacturing techniques.

The National Renewable Energy Laboratory (NREL) has been at the forefront of technological innovation within the PV industry. Many of the current industry cells in production have been improved through partnerships with NREL, either in full development partnerships, improvements, thus creating intellectual property (IP), or performance characterization and validation.

HWCVD, also known as catalytic CVD (Cat-CVD), has emerged as a new technology for depositing materials at low temperatures without the use of plasma to decompose source gases.  Since this technique is thermal in nature, it relies on a heated metal filament to decompose the gas species. Because there is no ion bombardment (as in PECVD), there is minimal substrate damage.  HWCVD also allows for low pressures that can be used for gas phase decomposition, thereby making the technique ideal for material etching. In HWCVD, the substrate is decoupled from the deposition process; therefore, substrates can be introduced and removed from the deposition chamber without disturbing the deposition process.  In addition, step coverage is excellent and uniformity can be readily optimized through adjustments of key deposition parameters.

NREL has been working within HWCVD industry for almost 20 years and holds a number of patents and pending patent applications, specifically in epitaxial Si growth by HWCVD. NREL researchers have developed a method for producing epitaxial Si films on a substrate using HWCVD by controlling the rate of Si deposition in a temperature range that spans the transition from a monohydride to a hydrogen free Si surface in a vacuum to obtain phase-pure epitaxial Si film of increased thickness. This method results in an order of magnitude increase in both the deposition rate and achievable thickness of epitaxy by HWCVD at substrate temperatures above 620°C. Deposition rates of 1.8 µm/min have been demonstrated, with no limit to the total epitaxial layer thickness.

  • Reduces manufacturing costs
  • Scalable
  • Lower temperature deposition
  • Rapid and controllable growth
  • Control of the surface morphology during the growth
Applications and Industries
  • Solar cells
  • Thin-film transistors
  • Light emitting diodes
  • Gas sensors
  • Electrochromic windows
  • Organic devices
  • Micromechanical structures
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 7,601,215
Method for rapid, controllable growth and thickness, of epitaxial silicon films
A method of producing epitaxial silicon films on a c-Si wafer substrate using hot wire chemical vapor deposition by controlling the rate of silicon deposition in a temperature range that spans the transition from a monohydride to a hydrogen free silicon surface in a vacuum, to obtain phase-pure epitaxial silicon film of increased thickness is disclosed. The method includes placing a c-Si substrate in a HWCVD reactor chamber. The method also includes supplying a gas containing silicon at a sufficient rate into the reaction chamber to interact with the substrate to deposit a layer containing silicon thereon at a predefined growth rate to obtain phase-pure epitaxial silicon film of increased thickness.
National Renewable Energy Laboratory 10/13/2009
Patent 6,251,183
Rapid low-temperature epitaxial growth using a hot-element assisted chemical vapor deposition process
The invention provides a process for depositing an epitaxial layer on a crystalline substrate, comprising the steps of providing a chamber having an element capable of heating, introducing the substrate into the chamber, heating the element at a temperature sufficient to decompose a source gas, passing the source gas in contact with the element; and forming an epitaxial layer on the substrate.
National Renewable Energy Laboratory 06/26/2001
Patent 7,122,736
Method and apparatus for fabricating a thin-film solar cell utilizing a hot wire chemical vapor deposition technique
A thin-film solar cell is provided. The thin-film solar cell comprises an a-SiGe:H (1.6 eV) n-i-p solar cell having a deposition rate of at least ten (10) .ANG./second for the a-SiGe:H intrinsic layer by hot wire chemical vapor deposition. A method for fabricating a thin film solar cell is also provided. The method comprises depositing a n-i-p layer at a deposition rate of at least ten (10) .ANG./second for the a-SiGe:H intrinsic layer.
National Renewable Energy Laboratory 10/17/2006
Patent 8,642,450
Low temperature junction growth using hot-wire chemical vapor deposition
A system and a process for forming a semi-conductor device, and solar cells (10) formed thereby. The process includes preparing a substrate (12) for deposition of a junction layer (14); forming the junction layer (14) on the substrate (12) using hot wire chemical vapor deposition; and, finishing the semi-conductor device.
National Renewable Energy Laboratory 02/04/2014
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 96-39, 01-03, 02-31, 6-20DevelopmentAvailable12/20/201212/27/2013

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To: Bill Hadley<>