In-Situ Sensors for Process Control of CuIn(Ga)Se2 Module Deposition: Annual Technical Report, 15 February 1998 - 15 February 1999

Materials Research Group (MRG), Inc. is developing in-situ sensors to improve yield, reproducibility, average efficiency, and prevention of 'lost processes'. In-situ X-ray fluorescence (XRF) will be used to monitor composition and thickness of deposited layers, and in-situ optical emission spectroscopy (OES) will be used to provide real-time feedback describing the deposition plasma.Characterization techniques are to be examined ex-situ in the first two years of the contract, and applied to existing deposition systems in the final year. Progress toward achieving these goals during Phase I includes: a)Development and verification of an XRF simulation tool to troubleshoot measurements, to predict difficulties in XRF interpretation, and to calculate quantities needed in thetranslation from XRF signal to composition; b) Examination of the implication of sample conditions unique to CIGS photovoltaics - such as varying Ga gradients, intermediate film thicknesses where neither thick-film nor thin-film approximations are valid, variations in back-contact thickness, multiple layers, variations in substrate composition and thickness - on XRF interpretation; c)Fabrication of CIGS samples and test structures for XRF measurements; d) Execution and interpretation of XRF measurements examining system accuracy; e) Design of a prototype XRF sensor built entirely of cost-effective, commercially available components that are suitable for integration into closed-loop deposition control; f) Evaluation of pulsed DC sputtering of Se; and g) interaction with CISNational Team industrial partners to specify and adapt sensor functions.