Fault detection of a semiconductor processing tool employs several techniques
to improve accuracy. One technique is sensor grouping, wherein a fault detection
index is calculated from a group of tool operational parameters that correlate
with one another. Another technique is sensor ranking, wherein sensors are accorded
different weights in calculating the fault detection index. Improved accuracy in
fault detection may be accomplished by employing a variety of sensor types to predict
behavior of the semiconductor processing tool. Examples of such sensor types include
active sensors, cluster sensors, passive/inclusive sensors, and synthetic sensors.
