Killer particles causing IC failure are normally large in size, and along with missing patterns. These particles are normally the root causes of most cluster defects, can be induced by a tool or a process, and are usually recognized by in-line optical metrology. High particle counts are normally caused by a tool malfunction. Particles smaller than 1 µm are normally not detected by means of optical inline metrology immediately after they are deposited; instead, they are observed when the particle size is magnified by subsequently deposited layers, which makes them visible to inline defect metrology tools.