Inspection method and inspection apparatus
A high resolution optical image is acquired by irradiating a mask with light emitted by a light source via a high resolution optical system. A low resolution optical image is acquired by irradiating the same mask with the light via a low resolution optical system. The design data of the mask pattern is corrected in light of shapes and dimensions determined according to at least one of a manufacturing process of the mask and a manufacturing process of a semiconductor device to be manufactured by transferring the mask pattern to a semiconductor wafer. Reference image data are generated corresponding to the high resolution optical image and the low resolution optical image. Whether the defect detected in the high resolution optical image is true or false is determined according to information of the defect detected in the low resolution optical image.
1. An inspection method comprising:
acquiring first optical image data of a pattern arranged on a mask by irradiating the mask with light emitted by a light source via a first optical system and directing the light transmitted through or reflected by the mask to be incident on an imaging device;
acquiring second optical image data of the pattern by irradiating the mask with light emitted by the light source via a second optical system and directing the light transmitted through or reflected by the mask to be incident on the imaging device, wherein the second optical system has a resolution lower than the first optical system and simulates an optical system of an exposure apparatus to be used to transfer the pattern of the mask to a semiconductor wafer;
generating first reference image data corresponding to the first optical image data and second reference image data corresponding to the second optical image data based on corrected design data, wherein the corrected design data is created by correcting design data for the pattern of the mask in light of shapes and dimensions of the pattern of the mask determined according to at least one of a manufacturing process of the mask and a manufacturing process of a semiconductor device to be manufactured by transferring the pattern of the mask on the semiconductor wafer;
detecting a defect of the pattern in the first optical image data by comparing the first optical image data with the first reference image data;
detecting a defect of the pattern in the second optical image data by comparing the second optical image data with the second reference image data; and
determining whether the detected defect in the first optical image data is a true defect or a false defect in reference to information of the detected defect in the second optical image data and evaluating transferability of the detected defect to the semiconductor wafer.
2. The inspection method according to claim 1 , wherein the shapes and the dimensions of the pattern determined according to the manufacturing process of the semiconductor device are estimated based on a difference between a measured value and a design value of dimensions of a certain portion of the pattern of the mask.
3. The inspection method according to claim 1 , wherein generating the first reference image data and the second reference image data includes filtering an image data created based on the corrected design data, and
further comprising adjusting simulation of characteristics of the resolutions of the first optical system and the second optical system, and parameters of image generation of the imaging device so as to minimize each of a difference between the first optical image data and the first reference image data and a difference between the second optical image data the second reference image data.
4. The inspection method according to claim 2 , wherein generating the first reference image data and the second reference image data includes filtering an image data created based on the corrected design data, and
further comprising adjusting simulation of characteristics of the resolutions of the first optical system and the second optical system, and parameters of image generation of the imaging device so as to minimize each of a difference between the first optical image data and the first reference image data and a difference between the second optical image data the second reference image data.
5. An inspection method comprising:
acquiring optical image data of a pattern arranged on a mask by irradiating the mask with light emitted by a light source via an optical system and directing the light transmitted through or reflected by the mask to be incident on an imaging device;
generating reference image data corresponding to the optical image data based on corrected design data, wherein the corrected design data is created by correcting design data for the pattern of the mask in light of shapes and dimensions of the pattern of the mask determined according to at least one of a manufacturing process of the mask and a manufacturing process of a semiconductor device to be manufactured by transferring the pattern of the mask to a semiconductor wafer;
detecting a defect of the pattern in the optical image data by comparing the optical image data with the reference image data;
estimating a shape of the defect to be transferred to the semiconductor wafer by use of an optical image data of the defect of the pattern detected in the optical image data, the reference data corresponding to the optical image data, and the corrected design data of the pattern, and estimating a first transfer image as transferred to the semiconductor wafer, based on data in which information on the estimated shape of the defect is added to the corrected design data, using a condition where the pattern arranged on the mask is transferred to the semiconductor wafer;
estimating a second transfer image of the pattern to be transferred on the semiconductor wafer, based on the corrected design data, by use of the condition where the pattern of the mask is transferred to the semiconductor wafer; and
determining whether the detected defect is true or false by comparing the first transfer image and the second transfer image and evaluating transferability of the detected defect to the semiconductor wafer.
6. An inspection apparatus comprising:
a light source;
a stage on which a mask is places;
an optical system having a variable numerical aperture and directing light emitted by the light source to irradiate the stage;
an imaging device that acquires optical image data of the mask placed on the stage by directing light emitted by the light source, through the optical system, and transmitted through or reflected by the mask to be incident on the imaging device;
a reference image generator that generates reference image data corresponding to the optical image data based on corrected design data, wherein the corrected design data is created by correcting design data for the pattern of the mask in light of shapes and dimensions of the pattern of the mask determined according to at least one of a manufacturing process of the mask and a manufacturing process of a semiconductor device to be manufactured by transferring the pattern of the mask to a semiconductor wafer;
a comparator that compares the optical image data with the reference image data to detect a defect of the pattern in the optical image data; and
a defect analyzer that analyzes the defect detected in the comparator by comparing first optical image data acquired by the imaging device using the numerical aperture as a value that is required to detect a defect of the pattern with first reference image data generated by the reference image generator, based on information on a defect detected in the comparator by comparing a second optical image data acquired by the imaging device using the numerical aperture as a value that simulates an optical system of an exposure apparatus to be used to transfer the pattern to the semiconductor wafer with second reference image data generated by the reference image generator.