A system and method of controlling a semiconductor wafer fabrication process. The method includes positioning a semiconductor wafer on a wafer support assembly in a wafer processing module. A signal is transmitted from a signal emitter positioned at a predetermined transmission angle relative to an axis normal to the wafer support assembly to check leveling of the wafer in the module, so that the signal is reflected from the wafer. The embodiment includes monitoring for the reflected signal at a predetermined reflectance angle relative to the axis normal to the wafer support assembly at a signal receiver. A warning indication is generated if the reflected signal is not received at the signal receiver.