Sensors for dynamically detecting substrate breakage and misalignment of a moving substrate

An apparatus and method incorporating at least two sensors that detect the presence of a substrate is provided. In one embodiment, a method for transferring a substrate in a processing system is described. The method includes positioning a substrate on an end effector in a first chamber, moving the substrate through an opening between the first chamber and a second chamber along a substrate travel path, and sensing opposing sides of the substrate travel path using at least two sensors positioned proximate to the opening, each of the at least two sensors defining a beam path that is directed through opposing edge regions of the substrate when at least a portion of an edge region traverses the beam path.