Method and apparatus for in-line process control of the cigs process
View Patent ↗An in-line production apparatus and a method for composition control of copper indium gallium diselenide (CIGS) solar cells fabricated by a co-evaporation deposition process. The deposition conditions are so that a deposited Cu-excessive overall composition is transformed into to a Cu-deficient overall composition, the final CIGS film. Substrates with a molybdenum layer move through the process chamber with constant speed. The transition from copper rich to copper deficient composition on a substrate is detected by using sensors which detect a physical parameter related to the transition. A preferred embodiment sensors are provided that detect the composition of elements in the deposited layer. A controller connected to the sensors adjusts the fluxes from the evaporant sources in order provide a CIGS layer with uniform composition and thickness over the width of the substrate.
1. An in-line continuous substrate flow production apparatus for fabrication of copper indium gallium diselenide (CIGS) solar cells, comprising:
a CIGS process chamber comprising a deposition zone (DZ) therein, the deposition zone configured for substrates provided with a molybdenum back contact layer to be continuously moved therethrough,
the process chamber further comprising:
a plurality of separated substrate heaters,
evaporation sources with Cu, In, Ga and Se, the evaporation sources configured to produce evaporant fluxes for depositing respective amounts of Cu, In, Ga and Se to a substrate, the evaporation sources provided in respective rows over a width of the substrate,
source heaters provided with said evaporation sources,
at least one composition detection device for detecting, in a deposited CIGS film at each of the rows, respective amounts of elements deposited by said evaporation sources, and
a controller connected to said at least one composition detection device, the controller adapted to adjust the evaporant fluxes in each of the respective rows in response to a detected variation, in the CIGS film, of the respective amounts deposited of each element in order to provide a CIGS layer having a uniform composition of elements.
2. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein said controller being adapted to adjust the evaporant fluxes in the respective rows in order to provide a CIGS film of uniform thickness.
3. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein two rows of vapour sources are arranged over a width of the process chamber as seen in a transport direction of the substrates, the two rows of evaporation sources being arranged at each side of and outside a path along which the substrates flow through the deposition chamber.
4. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein said at least one composition detection device is provided within the process chamber.
5. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein said at least one composition detection device is provided outside the process chamber.
6. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein the evaporant vapor sources are arranged at a level below the substrates.
7. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein said at least one composition detection device is one of an X-ray fluorescence device or an EDX (energy dispersion X-ray spectroscopy) device adapted to measure total deposited amounts of each element and to measure the thickness of the CIGS layer.
8. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein the controller is adapted to receive an input signal representative of total deposited amounts of each element and, in response to said input signal, adjust the evaporant fluxes from the evaporant sources in order to provide a uniform thickness of the CIGS film.
9. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein said at least one composition detection device is a device that measures the composition of the CIGS layer indirectly by calibrating against a physical parameter to obtain a measure of an amount of Cu, Ga, and In.
10. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein said at least one composition detection device is a resistance measuring device.
11. The in-line continuous substrate flow production apparatus in accordance with claim 1 , further comprising:
a separate thickness measuring device connected to the controller for measuring the thickness of the deposited CIGS film, the controller being adapted to, in response to a detected thickness variation, adjust the evaporant fluxes from the evaporant sources in order to provide a uniform thickness of the CIGS film.
12. The in-line continuous substrate flow production apparatus in accordance with claim 11 , wherein the thickness measuring device is a profilometer.
13. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein the evaporant sources with Cu, Ga and In are arranged in an order of: Ga, followed by Cu, followed by In, with respect to a transport direction of the substrates.
14. The in-line continuous substrate flow production apparatus in accordance with claim 13 , wherein a further evaporation source with Ga is arranged downstream the In evaporation source with respect to the transport direction of the substrates.
15. The in-line continuous substrate flow production apparatus in accordance with claim 1 , wherein there are evaporant sources with Cu, Ga and In and the evaporation sources are arranged in the following order as seen in the transport direction of a substrate: In, Cu, Ga.
16. The in-line continuous substrate flow production apparatus in accordance with claim 15 , wherein a further evaporation source with In arranged downstream the Ga evaporation source.