Scanning electron microscope and method for processing an image obtained by the scanning electron microscope
View Patent ↗In the case where a specimen is imaged by a scanning electron microscope, it is intended to acquire an image of a high quality having a noise component reduced, thereby to improve the precision of an image processing. The intensity distribution of a beam is calculated on the basis of an imaging condition or specimen information, and an image restoration is performed by using a resolving power deterioration factor other than the beam intensity distribution as a target of a deterioration mode, so that a high resolving power image can be acquired under various conditions. In the scanning electron microscope for semiconductor inspections and semiconductor measurements, the restored image is used for pattern size measurement, defect detections, defect classifications and so on, so that the measurements can be improved in precision and so that the defect detections and classifications can be made high precise.
1. A scanning electron microscope device comprising:
a charged particle beam irradiating system for irradiating and scanning a specimen having a pattern with a charged particle beam;
a charged particle detecting system for detecting charged particles of the kind identical to or different from charged particles emitted from said specimen, which was irradiated and scanned with the charged particle beam by said charged particle beam irradiating system;
an image acquiring unit configured for acquiring a charged particle image of said specimen by processing a signal detected by said charged particle detecting system;
an image processing unit configured for processing the charged particle image of said specimen acquired by said image acquiring unit; and
a storage unit configured for storing plural parameters corresponding to plural imaging conditions for calculating point spread functions;
wherein said image processing unit determines a restored image of the acquired image by using a point spread function, which is a function expressing a resolving power deterioration model determined from a dispersion distribution of the charged particles in the specimen.
2. The scanning electron microscope device according to claim 1 ,
wherein the point spread function is a function expressing a resolving power deterioration model determined from a dispersion distribution of the charged particles in the specimen and a divergence of the charged particles on the specimen.
3. The scanning electron microscope device according to claim 1 ,
wherein the point spread function is calculated based on a parameter being selected from the stored plural parameters corresponding to plural imaging conditions as the one corresponding to an imaging condition of at least one of a shape of specimen and a material of specimen.
4. The scanning electron microscope device according to claim 1 ,
wherein a shape of the point spread function is changed with the charged particle beam irradiation position.
5. The scanning electron microscope device according to claim 1 ,
wherein said image processing unit is configured to perform, by using the restored image determined, any of a defect detection of a pattern on said specimen, a defect classification of the pattern on said specimen, and a measurement of the size and shape of the pattern on said specimen.
6. The scanning electron microscope device according to claim 1 ,
wherein said image processing unit determines the restored image from said acquired image by using said point spread function and information of a noise component of said acquired image, with the noise component independent from said point spread function.
7. A scanning electron microscope method comprising:
a charged particle beam irradiating step for irradiating and scanning a specimen having a pattern with a charged particle beam;
a charged particle detecting step for detecting charged particles of the kind identical to or different from charged particles emitted from said specimen, which was irradiated and scanned with the charged particle beam by said charged particle beam irradiating step;
an image acquiring step for acquiring a charged particle image of said specimen by processing a signal detected by said charged particle detecting step;
an image processing step for processing the charged particle image of said specimen acquired by said image acquiring step; and
a storage step for storing plural parameters corresponding to plural imaging conditions for calculating point spread functions,
wherein said image processing step determines a restored image of the acquired image by using a point spread function, which is a function expressing a resolving power deterioration model determined from a dispersion distribution of the charged particles in the specimen.
8. The scanning electron microscope method according to claim 7 ,
wherein the point spread function is a function expressing a resolving power deterioration model determined from a dispersion distribution of the charged particles in the specimen and a divergence of the charged particles on the specimen.
9. The scanning electron microscope method according to claim 7 ,
wherein the point spread function is calculated based on a parameter being selected from the stored plural parameters corresponding to plural imaging conditions as the one corresponding to an imaging condition of at least one of a shape of specimen material of specimen.
10. The scanning electron microscope method according to claim 7 ,
wherein a shape of the point spread function is changed with the charged particle beam irradiation position.
11. The method according to claim 7 , further comprising a step of:
using the restored image to perform any of a defect detection of a pattern on said specimen, a defect classification of the pattern on said specimen, and a measurement of the size and shape of the pattern on said specimen.
12. The method according to claim 7 ,
wherein said image processing step determines the restored image from said acquired image by using said point spread function and information of a noise component of said acquired image, with the noise component independent from said point spread function.