semiday

The wafer was polluted and contaminated because he already opened the wafer on the FAB, but you could find the planted defects on the wafer.

If the wafer was polluted too much after using it, you can clean the wafer on the wet cleaning tool then you could see the planted defects clearly.

Above photos is one die which have the planted defects (program defects) which are white dots and were located at every 2 dies, the die size is 10.37mm × 7.23mm. The program defects planted various sizes and types.