Method and device for detecting defects and method and device for observing defects
View Patent ↗The present invention is suppressing the elongating phenomenon in the dark field image of defects in detecting a minute defect by using a dark field microscope. Provided is a method for detecting defects in which scattered light generated from the sample, is concentrated to form an image and is captured and processed to extract a defect to find the positional information of the defect, and the positional information is output, wherein an image of the scattered light that suppresses the occurrence of the elongating phenomenon is formed for which partial shielding of a component of the forward scattered light, that passes through a region near the outer edge of the field of view of the objective lens, and the positional information for the defect is found from a luminance signal for a defect that is extracted from a captured scattered light image that suppresses the occurrence of the elongating phenomenon.
1. A defect detecting method comprising the steps of:
irradiating a sample with a light from a light source of an illumination optical system arranged such that said light is incident on a surface of the sample from an oblique direction;
condensing scattered light generated from the sample irradiated with the light and incident on an objective lens to focus an image of the scattered light;
acquiring said image by using a controller to adjust a position of said objective lens with respect to the sample such that the focused image of the scattered light is focused onto a detection face of an imaging element;
extracting a defect on the sample by processing the acquired image using a signal processor configured to calculate position information of the extracted defect; and
outputting the calculated position information of the defect to a display,
wherein in focusing the image of the scattered light, the controller is configured to suppress an occurrence of a elongating phenomenon by the scattered light scattered to a region near to an outer edge portion of an aperture of the objective lens by focusing a light partially shielding a component of the scattered light transmitting the region near to the outer edge portion of the aperture of the objective lens in the scattered light generated at the surface of the sample by irradiating the light in the scattered light incident on the objective lens, and
wherein the position information of the extracted defect is calculated by the signal processor based on a luminance gravity center of the defect extracted from the image acquired by taking the image of the scattered light suppressing the occurrence of the elongating phenomenon by the scattered light scattered to the region near to the outer edge portion of the aperture of the objective lens.
2. The defect detecting method according to claim 1 , wherein the scattered light incident on the objective lens is shielded in a shape of a concentric circle for a visual field of the objective lens.
3. The defect detecting method according to claim 1 , wherein a portion of the region generating the scattered light scattered to the region near to the outer edge portion of the aperture of the objective lens is partially shielded for the aperture of the objective lens in the scattered light incident on the objective lens.
4. A defect detecting device comprising:
mounting stage which mounts a sample;
an illumination optical system which irradiates the sample by making a light incident on a surface of the sample mounted on the mounting stage from an oblique direction;
a focusing optical system including an objective lens which condenses a scattered light generated from the sample irradiated with the light by the illumination optical system, a focusing lens for focusing an image of the scattered light condensed by the objective lens, and an image taking element for taking an image of the scattered light focused by the focusing lens;
an image processor configured to extract a defect on the sample by processing an image of the scattered light provided by taking the image of the scattered light using the focusing optical system, and calculating position information of the extracted defect; and
a display which outputs the position information of the defect calculated by the image processor,
wherein the focusing optical system further includes a filter for partially shielding a scattered light scattered to a region near to an outer edge portion of an aperture of the objective lens in the scattered light incident on the objective lens, an image of the scattered light suppressing an occurrence of a elongating phenomenon by the scattered light scattered to the region near to the outer edge portion of the aperture of the objective lens is focused by focusing the scattered light transmitted through the filter by the focusing lens, and an image of the scattered light focused and suppressing the occurrence of the elongating phenomenon is taken by the image taking element, and
wherein the image processor calculates the position information of the defect based on a luminance signal of the defect extracted from the image acquired by taking the image of the scattered light suppressing the occurrence of the elongating phenomenon.
5. The defect detecting device according to claim 4 , wherein the filter shields the scattered light incident on the objective lens in a shape of a concentric circle for a visual field of the objective lens.
6. The defect detecting device according to claim 4 , wherein the filter partially shields a portion of the region for generating the scattered light scattered to the region near to the outer edge portion of the objective lens for the aperture of the objective lens in the scattered light incident on the objective lens.