To obtain good reliability information, many fabs are investing in wide area networks in which the status of hundreds of pumps, local scrubbers or gas cabinets can be centrally monitored by computer. Key parameters are monitored locally at each system and are transmitted onto the network for display, analysis or storage, as required. Fault situations are immediately flagged as warnings or alarms, and service personnel can be notified automatically. However, the network also provides a new capability of tapping into a wide range of diagnostic information, either locally or remotely. When analysed by an experienced technician, anomalous situations or behaviour indicative of impending failure can be spotted in time to take corrective action.
New sensors can contribute much to an understanding of the internal state of a vacuum system.
For example, a deposition sensor can be installed into an exhaust pipeline or into a vacuum foreline, allowing continuous monitoring of the thickness of deposit on the inside surfaces of the pipe. Using a special arrangement of capacitor electrodes, by-product thickness in excess of 20mm can be monitored for a wide variety of depositing materials, with the data being fed onto a network or recorded by a data logging system. Although such sensors can be calibrated, their main value is to indicate a departure from an expected trend, or the extrapolation of a known trend to a predetermined action point. Progress in data acquisition and diagnostics may eventually lead to the ultimate goal of realistic prediction algorithms. This will be a big step, with many issues yet to be resolved.