Large Particle Detection For Multi-Spot Surface Scanning Inspection Systems

摘要

The illumination power density of a multi-spot inspection system is adjusted in response to detecting a large particle in the inspection path of an array of primary illumination spots. At least one low power, secondary illumination spot is located in the inspection path of an array of relatively high power primary illumination spots. Light scattered from the secondary illumination spot is collected and imaged onto one or more detectors without overheating the particle and damaging the wafer. Various embodiments and methods are presented to distinguish light scattered from secondary illumination spots. In response to determining the presence of a large particle in the inspection path of a primary illumination spot, a command is transmitted to an illumination power density attenuator to reduce the illumination power density of the primary illumination spot to a safe level before the primary illumination spot reaches the large particle.