AUTOMATIC PROBLEM DETECTION AND DOCUMENTATION IN A PLASMA ETCH REACTOR

IC manufacturing involves a large number of complex process steps. There is a probability of a misprocessing error in each of these steps. Unless the individual process step is followed by an inspection of every wafer, the consequences of such errors can become severe. First, these process errors can propagate for a large number of wafers, thereby decreasing the yield. In addition, if a misprocessed wafer continues down the production sequence it incurs a lot of needless, expensive processing. Finally, when a problem is detected, the original cause can be difficult and expensive to determine. This paper describes two software tools, in a single-wafer plasma etcher, that have been developed to minimize the occurence and maximize the efficiency of the diagnosis of such misprocessing. The first examines the endpoint trace of every wafer and determines if that wafer has seen anomalous processing. If so, the software can terminate the processing of subsequent wafers. The second records the analog values of all the process control parameters during the entire etch process. When these two routines are linked appropriately, it is possible to record these analog values for only those wafers that have seen anomalous processing. This feature provides data for the analysis of the process problem. These procedures thus act to minimize the number of wafers that are misprocessed, and provide pertinent diagnostic information for those that have been.