Method and apparatus for in-line process control of the cigs process

Abstract

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. 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 CIGS 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 for depositing a CIGS film on a surface of the 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 that detects respective amounts of elements on the surface of the substrate, and 
 a controller connected to said at least one composition detection device, the controller configured to adjust the evaporant fluxes from each of the evaporant sources in response to a detection of a variation, detected by the at least one composition detection device, of the respective amounts of elements in the CIGS film on the surface of the substrate, so that the CIGS film is deposited by the evaporation sources to have a uniform composition. 
   
     
     
         2 . The in-line continuous substrate flow production apparatus in accordance with  claim 1 , wherein said controller adjusts the evaporant fluxes in the respective rows so that the CIGS film has a uniform thickness. 
     
     
         3 . The in-line continuous substrate flow production apparatus in accordance with  claim 1 , wherein two rows of evaporation 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 located 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 located outside the process chamber. 
     
     
         6 . The in-line continuous substrate flow production apparatus in accordance with  claim 1 , wherein the evaporation 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, said at least one composition device configured to measure total deposited amounts of each element and to measure a thickness of the CIGS film. 
     
     
         8 . The in-line continuous substrate flow production apparatus in accordance with  claim 1 , wherein the controller is configured 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 to form the CIGS film with a uniform thickness. 
     
     
         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 a layer of elements on the substrate 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 a thickness of the CIGS film on the substrate, the controller being configured to, in response to a detected thickness variation, adjust the evaporant fluxes from the evaporant sources so that the CIGS film is deposited by the evaporation sources to have a uniform thickness.   
     
     
         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 evaporation 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 the evaporation sources with Cu, Ga and In are arranged in the following order as seen in a 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 is arranged downstream the Ga evaporation source with respect to the transport direction of the substrates.