Detection of wafer fragments in a wafer processing apparatus

Abstract

During a wafer process, fragments can break away from a wafer. The wafer fragments can compromise the accuracy of the temperature signals generated by sensor probes in a rapid thermal process. In particular, the fragments can attenuate or otherwise interfere with the radiation received from the wafer. This interference can undermine the accuracy of the temperature measurement signal generated by the probes. If the temperature control function is compromised, excessive temperature gradients can result in damage to the wafer, reducing device yield and degrading device quality. To alleviate the effects of wafer fragments, the presence of a wafer fragment is detected. An image acquisition device acquires an image of an area adjacent the sensor probe. A processor analyzes the acquired image to determine whether a wafer fragment is present. One approach involves comparing the acquired image to a reference image taken in the absence of a wafer fragment quantifying the amount of deviation. Another approach involves analyzing the acquired image for optical density contrast changes indicative of the presence of a wafer fragment. Detection of a wafer fragment allows the rapid thermal process to be stopped so that the fragment can be cleared away, either manually or automatically, prior to insertion of the next wafer into the chamber.