Wafer level tracking enhances particle source isolation in a manufacturing environment

The successful manufacture of ULSI integrated circuits at Digital now requires the elimination of particle nucleation sites whose size can be well below the resolution of available on-line defect detection tools. Traditional sequential wafer inspections can often find specific operations which give rise to particles, but they may slow production to unacceptable levels, especially when problems are intermittent. This paper documents a new strategy which combines randomization of wafer order with wafer level tracking and patterned wafer particle detection to detect submicron sources of defects. Case studies illustrate the ability of this method to detect nucleation sites invisible to defect detection systems, and reduce the number of inspections required to trace specific defect sources. Cases where application of this technique should not be used are also provided.