Non-contacting deposition control of chalcopyrite thin films
AssigneeEnergy Photovoltaics, Inc.
InventorAlan E. Delahoy
Life of this patent
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Abstract
Chalcopyrite semiconductors, such as thin films of copper-indium-diselenide (CuInSe2), copper-gallium-diselenide (CuGaSe2), and Cu(Inx,Ga1-x)Se2, all of which are sometimes generically referred to as CIGS, have become the subject of considerable interest and study for semiconductor devices in recent years. They are of particular interest for photovoltaic device or solar cell absorber applications. The quality of Cu(In,Ga)Se2 thin films, as an example of chalcopyrite films, is controlled by making spectrophotometric measurements of light reflected from the film surface. This permits the result of non-contacting measurements of films in a continuous production environment to be fed back to adjust the production conditions in order to improve or maintain the quality of subsequently produced film.
Claims8
A method for depositing a chalcopyrite structured semiconductor thin film onto a substrate from at least a first source and a second source, and controlling the thin film's achievable solar conversion efficiency;
- comprising:
- a) controlling the first source-to produce a first particle flux incident on the substrate and controlling the second source to produce a second particle flux incident on the substrate, thereby producing a first deposited thin film;
- b) monitoring the first deposited thin film's achievable solar conversion efficiency by:
- i) irradiating at least a portion of said first deposited thin film's surface with light comprising a plurality of wavelengths;
- ii) detecting light reflected from said first deposited thin film's surface with a spectrophotometric device that produces an output signal directly related to the color of said first deposited thin film's surface;
- and
- iii) comparing the output signal with a predetermined measure of the achievable solar conversion efficiency of said first deposited thin film and producing a control signal thereby;
- c) feeding said control signal back so as to control at least one of the first source and the second source in order to produce a second deposited thin film of better achievable solar conversion efficiency than the said first deposited thin film.
A method for depositing a chalcopyrite structured semiconductor thin film onto a substrate from at least a first source and a second source, and controlling the thin film's achievable solar conversion efficiency;
- comprising:
- a) controlling the first source to produce a first particle flux incident on the substrate and controlling the second source to produce a second particle flux incident on the substrate, thereby producing a first deposited thin film;
- b) monitoring the first deposited thin film's achievable solar conversion efficiency by:
- i) irradiating at least a portion of said first deposited thin film's surface with light comprising a plurality of wavelengths;
- ii) detecting light reflected from said first deposited surface with a spectrophotometric device that produces an output signal directly related to the color of said first deposited thin film's surface;
- and
- iii) comparing the output signal with a predetermined measure of the achievable solar conversion efficiency of said first deposited thin film and producing a control signal thereby;
- c) feeding said control signal back so as to control at least one of the first source and the second source in order to produce a second deposited thin film of better achievable solar conversion efficiency than said first deposited thin film, wherein said first and second deposited thin films consist essentially of Cu(In,Ga)Se2, and the output signal of the spectrophotometer identifies said first deposited surface's reflectance at at least a first and a second discrete preselected wavelength;
- the method further comprising computing a quality function directly related to a ratio of said first deposited thin film's surface's reflectance at the first discrete preselected wavelength and said first deposited thin film's surface's reflectance at the second discrete preselected wavelength and using the quality function to generate the control signal.
Dependencies are inferred from the claim text.