Thickness and Conductivity Analysis of Molybdenum Thin Film in CIGS Solar Cells Using Resonant Electromagnetic Testing Method

This paper presents an analysis method that combines the nondestructive resonant electromagnetic testing and the mathematical model for determining the thickness and conductivity of molybdenum (Mo) thin layer in copper indium gallium selenide (CIGS) solar cells. This technique is demonstrated for Mo layers (0.5-1.5 μm) over glass substrate. The impedance of probe coils and sheet resistance were measured by using 4294A Hewlett-Packard impedance analyzer and RT-9 Napson four-point probe to verify the analytical data. Analytic solutions for calculating the coil impedance of EC probe above Mo thin layers are presented. The conductivity is considered with sheet resistances and thicknesses. The estimation of thickness and sheet resistance of Mo thin layers is based on the linear regression of the measured data and theoretical calculations. As anticipated, the proposed method shows that the coil's impedance largely relates to the sheet resistance and the thickness of Mo layers. Two Mo layers with different manufacturing process and unknown characteristics also inspected and analyzed for comparison. The results show that the agreement between experimental and analytical data is within a small deviation.