1. Field of the Invention
The present invention relates to a defect review apparatus and a defect review method, and particularly relates to a defect review apparatus and a defect review method in which an observation of a defect is performed by irradiating a surface of a sample with an electron beam.
2. Description of the Related Art
Recently, patterns of wafers, photomasks, and the like have become finer due to finer designing of semiconductor devices, and finer defects have become more apt to largely affect the manufacturing yield. Thus, importance of defect inspection is increasing.
In such defect inspection of wafers and photomasks, an inspection using an optical inspection apparatus with high throughput is firstly performed. The optical inspection apparatus can detect an extremely fine defect, for example, a defect which is of 10 nm or smaller. However, due to limitations in resolution, the optical inspection apparatus cannot determine the shape of the defect.
In this respect, when a defect is detected by the optical inspection apparatus, the position, shape, and size of the defect are checked in a subsequent defect review process. In the defect review process, a scanning electron microscope (SEM) is used, and the shape of a fine defect which could not be measured by the optical inspection apparatus is measured based on a high resolution SEM image.
Moreover, Japanese Application Laid-Open Publication No. H3-192645 discloses a method of observing the shape of the surface of a sample three-dimensionally by using a scanning electron microscope in which multiple (two) electron detectors are installed.
In the defect review process described above, the defect has to be specified first in the SEM image. In this respect, the defect is detected by performing pattern matching (comparison process) between the SEM image of the sample and, for example, design data which represents a pattern with no defect.
However, a large amount of calculation is required in the defect detection by pattern matching, which takes a relatively long period. Thus, there is a problem that the defect review cannot be performed speedily.
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