DEPENDENCE OF OFFSET ERROR ON OVERLAY MARK STRUCTURES IN OVERLAY MEASUREMENT

Measurement precision, especially the offset error in the automatic measurement technique of overlay, was studied for sub-half-micron device manufacturing. Experimental data showed that the offset error depended on the cross-sectional structure rather than the reflectivity or the roughness of the measurement marks. Dependence of the offset error upon equipment factors, e.g., the incident angle of illumination, was also studied. The depth of focus was considerably increased up to 1.5-mu-m on the LSI wafers with well-aligned light. This paper also shows an offset error on critical levels in sub-half-micron device manufacturing.