Thin-film Si solar module production requires a fast wide area tool for layer characteristic measurement and control. Non-uniformity in layer deposition is expected to induce loss in module power. Simulations of amorphous Si modules using a two-dimensional model have been used to examine the efficiency loss associated with non uniformity of large scale monolithically integrated thin film modules. The results indicate that non uniform deposition significantly lowers the module efficiency, in a magnitude that varies depending on the shape and orientation of the deposition signature relative to the scribe lines. In order to control the deposition process of individual layers in layer stacks in thin-film PV modules a wide area metrology tools has been developed and tested. Example of layers maps obtained during production of Si layers module are shown. Comparisons of layer characteristics obtained using this tool and values obtained by conventional methods are given to validate the tool performances.