LSIウェハパターンからの反射光の解析

LSIウェハ上異物の自動検出技術の研究

抄録

Contaminants have a direct effect on LSI yield. At present, visual inspection of Si wafers for contaminant is an essential part of the semiconductor QC process. However, the conventional QC process requires much time and significantly limits LSI yield. Therefore, a means of detecting these particles to facilitate early rejection of the contaminated wafers is needed.
Several systems have been developed which automatically detect surface contaminants or particles on unpatterned wafers by measuring the intensity of scattered laser light. However, no system has yet been applied to inspecting patterned surface, because micro-patterns on the surfaces behave as diffraction gratings producing noise signals which are hard to distinguish from signals produced by particles.
In the present technique, information about particles is obtained by measuring the polarization of the scattered light. The basic idea in the present technique is that, if an analyzer placed behind the objective could cancel only the light reflected from the pattern, then the light reflected from contaminants would be readily detectable in the absence of pattern noise. Therefore, the relation is determined between the analyzer angle and the electric vector of the incident light which would effectively cancel the pattern noise. It has been verified that particles as small as 1μm could be detected from the pattern noise, by experiments.