Continuous in-line processing of CdS/CdTe devices: Process control using XRF and efficient heating

A simple, quick, and non-destructive way to measure deposited Cu, used for back contact formation, and thickness of CdS and CdTe layers in the device is desirable for manufacturing process control. A simple X-ray Fluorescence (XRF) system was investigated for these measurements. Experiments show that 5 min. polychromatic XRF spectra can be used to measure CdTe and CdS thickness, and accurate 30 sec. measurements are possible. Statistical integrity of Cu XRF measurements was investigated. XRF measurements are able to differentiate Cu concentrations within 10% of nominal, making it useful for process control. A description of a new, improved in-line R&D deposition system is also presented. Thermal modeling results show the new NiCr wire based heating system will reach desired operating temperatures while providing opportunities for improved temperature uniformity and energy usage.