Patterned wafer inspection method and apparatus therefor

Abstract

An electron beam (area beam) having a fixed area is irradiated onto the surface of a semiconductor sample, and reflected electrons from the sample surface are imaged by the imaging lens, and images of a plurality of regions of the surface of the semiconductor sample are obtained and stored in the image storage unit, and the stored images of the plurality of regions are compared with each other, and the existence of a defect in the regions and the defect position are measured. By doing this, in an apparatus for testing a pattern defect of the same design, foreign substances, and residuals on a wafer in the manufacturing process of a semiconductor apparatus by an electron beam, speeding-up of the test can be realized.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a method for testing the surface status of a sample (a semiconductor device, etc.) and apparatus therefor and particularly to an inspection method and apparatus therefor for imaging and inspecting fine pattern defects on the surface of a semiconductor device in high sensitivity and high resolution at high speed using an electron beam.[0003] 1. Description of the Prior Art[0004] As an inspecting method for detecting defects of a circuit pattern formed on a wafer by comparison test in the manufacturing process of a semiconductor device, there is a method for obtaining images of two or more same kind of LSI patterns on one wafer using light, comparing these plurality of images, and testing existence of pattern defects and it is already put into practical use. The outline of this inspecting method is described in "Monthly Semiconductor World", October issue, 1995, pp. 114 to 117. When pattern defects in the manufact...

AI Technical Summary

Benefits of technology

[0011] Namely, in the patterned wafer inspection method of the present invention, an electron beam from the electron source is sequentially irradiated to a plurality of irradiation regions (area regions) of the surface of a semiconductor sample as a so-called area beam, and enlarged images in the plurality of irradiation regions are sequentially formed by electron-optically imaging backscattering electrons from the plurality of irradiation regions or secondary electrons, and the enlarged images in the plurality of irradiation regions are sequentially converted to electrical image signals and stored, and a pattern defect in each of the aforementioned irradiation regions is detected by comparing the stored image signals in the plurality of irradiation regions with each other. According to this method, the conventional two-dimensional scanning by a spot beam in each irradiation region (area region) is not necessary, so that the inspection time can be greatly shortened and the defect test can be speeded up.

[0016] On the other hand, a method for setting so that the size of enlarged images on the surface of a semiconductor sample which can be obtained at the same time by irradiating an electron beam at the same time becomes almost equal to the size of the light receiving surface of the image detection device is simpler. On the other hand, by setting the size of the electron beam irradiation region so that the size of enlarged images on the surface of a semiconductor sample is made smaller than the size of the light receiving surface of the image detection device, scanning the electron beam on the surface of the semiconductor sample, then projecting the enlarged images overall the light receiving surface of the image detection device for a given period of time, and superimposing a signal for correcting the variation factors of irradiation position and irradiation range on the scanning signal of the electron beam, a method realizing higher precision may be available.

[0017] To decelerate an electron beam to be irradiated onto a semiconductor sample, make the energy value of the electron beam when it is irradiated onto the sample sufficiently smaller than the energy value before deceleration, and keep the energy dispersion of backscattering electrons generated from the sample surface by irradiation of the decelerated electron beam within a range that it will not affect the resolution of the imaging system, a negative potential is applied to the semiconductor sample. Or, by providing a filter for discriminating backscattering electrons generated by irradiation of the electron beam or secondary electrons in energy and imaging only backscattering electrons or secondary electrons with a specific energy width, the problem of high speed test can be solved and the resolution can be improved at the same time.

Problems solved by technology

When pattern defects in the manufacturing process of a semiconductor device are tested by such an optical inspecting method, residuals of a silicon oxide film through which light transmits and a photosensitive resist material cannot be detected.

However, since the electron beam is limited to a spot shape and this spot beam is two-dimensionally scanned on the surface of a sample, there is a limit to the high speed (shortening of the inspecting time).

There is also a limit to the large current of an electron beam to be used due to the brightness of the electron source used and space charge effect.

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