1. Field of the Invention
The present invention relates to an apparatus for observing in detail and classifying a defect on a semiconductor wafer detected by another inspection apparatus, in particular, relates to an apparatus and a method for inspecting a semiconductor defect for detecting patterning failure based on an image of a circuit pattern formed on the semiconductor wafer and further classifying the defect based on the defect occurrence factor.
2. Description of the Related Art
In recent years, as semiconductor circuit becomes complicated and refined in dimension, drop of yield due to frequent occurrence of patterning failure originating the manufacturing process of the semiconductor has become a problem. Also, because the factors of failures hidden in the manufacturing process are diversified, it is desired to automate the work for detecting the defect on the semiconductor wafer and determining the factor of the defect in order to inhibit the efficiency drop in developing the semiconductor wafer. In this connection, a technology for re-detecting the defect of a circuit pattern formed on a semiconductor wafer detected by another inspection apparatus is described in, for example, Japanese Unexamined Patent Application Publication No. 2000-030652.
In accordance with the method described in Japanese Unexamined Patent Application Publication No. 2000-030652, the substrate of the inspection object was photographed, an image of the inspection object pattern including a defect and an image of the reference pattern not including a defect were obtained, both images were compared, and the section where there was difference between two images was extracted as a defect. However, as refinement and densification of the circuit pattern progress, the defect of the pattern shape itself (systematic defect) which cannot be detected by comparison of image to image of such actual pattern has started to occur.
To solve this problem, a method for comparing the circuit pattern shape of an inspection object and a standard shape formed beforehand is proposed, and, as an example of it, Japanese Unexamined Patent Application Publication No. 2005-277395 is known.
Japanese Unexamined Patent Application Publication No. 2005-277395 describes a pattern inspection apparatus and a method for inspection by a pattern image of an inspection object photographed by a scanning electron microscope (hereinafter referred to as a “SEM”) and information of circuit design data.
More specifically, it describes a procedure for detecting a defect with an inter-edge deviation vector obtained by comparison of a standard pattern formed by adding shrinkage and modification of roundness for corner sections with respect to circuit design data and an inspection object pattern, a procedure for performing defect classification of the defect described above by ADC (Automatic Defect Classification) on an image basis, and a procedure for computing the pattern deformation quantity such as position shift quantity and wiring width deformation quantity based on the inter-edge deviation quantity in the portion other than the defect aiming the process control.
In detecting the defect portion by comparison with the standard pattern, it is necessary to prepare, as the standard pattern, the shape without a defect determined to be normal as a device (hereinafter referred to as “a normal shape”). However, the shape regarded as normal for a device has a certain allowable range of variation in the width, roundness and the like. Therefore, even if one standard pattern is formed for comparison imitating a normal shape, as in the pattern inspection method described in Japanese Unexamined Patent Application Publication No. 2005-277395, the shape may not necessarily be suitable for detection of the defect.
Also, even if the defect inspection is performed by picking up a certain process variation (exposure condition, for example), forming a plurality of shapes to reflect its variation, and comparing with the inspection object pattern images one by one, accuracy of inspection lowers with respect to the defect originated by the process variation other than the variation picked up. In addition, with respect to the defect occurring by combination of a plurality of process variation factors, it is difficult to find out its occurrence factor.