Surface inspection system with automatic discrimination of microscratches and particles on chemical mechanical polished wafers

Microscratches and particles are becoming a serious problem associated with the introduction of CMP to IC-processing. This paper describes a new surface inspection system for a blank wafer with emphasis on the discrimination technique between microscratches and particles. The system first detects both defects by means of the laser scattering technique as is the case of a conventional particle inspection tool, followed by a newly developed discrimination procedure based on the difference of angular distribution of the scattered light. The discrimination rate which is defined as the ratio of the correctly classified defects to the total defects detected was evaluated to be 85% or more on actual CMP-processed wafers.