Microscope system
Regarding a microscope system, a technique capable of suitably achieving a focusing on a surface of a sample is provided. The microscope system includes an irradiation optical system (laser light source 101 or the like) that irradiates a surface of a sample 3 on a stage 104 with light from an oblique direction, an observation optical system (camera 112 or the like) that forms an image of scattered light from the surface of the sample 3 , a focus mechanism (piezo stage 106 or the like) that changes a height position of focus with respect to the surface of the sample 3 , and a computer system 100 that acquires an image from the observation optical system. Regarding the sample 3 , the computer system acquires a first image in a first focus state and a second image in a second focus state, in which the first image and the second image have different focus heights, calculates an amount of change between a position of a first spot pattern in the first image and a position of a second spot pattern in the second image, calculates an amount of change in height of the sample 3 based on an incident angle in the oblique direction and the amount of change in position of spot pattern, and adjusts the height position of the focus by using the amount of change in sample height so as to focus on the surface of the sample 3.
1 . A microscope system comprising:
an irradiation optical system configured to irradiate a surface of a sample on a stage with light from an oblique direction;
an observation optical system configured to form an image of scattered light from the surface of the sample;
a focus mechanism configured to change height positions of focuses of the irradiation optical system and the observation optical system with respect to the surface of the sample; and
a computer system configured to control the irradiation optical system, the observation optical system and the focus mechanism, and acquire the image formed by the observation optical system, wherein
the computer system is configured to
regarding the sample, acquire a first image in a first focus state at a first time point and a second image in a second focus state at a second time point, the first image and the second image having different focus heights,
calculate a position of a spot pattern in the first image as a first spot position, and calculate a position of a spot pattern in the second image as a second spot position,
calculate an amount of change between the first spot position and the second spot position as an amount of change in spot position,
calculate an amount of change in height of the sample as an amount of change in sample height based on an incident angle between the oblique direction of the irradiating light and a normal to the surface of the sample and the amount of change in spot position, and
adjust the height positions of the focuses by using the amount of change in sample height so as to focus on the surface of the sample.
2 . The microscope system according to claim 1 , wherein
the incident angle in the oblique direction is set to 0, the amount of change in spot position is set to ΔD, and the amount of change in sample height is set to ΔZ, the computer system calculates the amount of change in sample height based on ΔZ=ΔD/tan θ as a calculation formula.
3 . The microscope system according to claim 1 , wherein
the irradiation optical system is a dark field optical system that radiates laser light as the light.
4 . The microscope system according to claim 1 , wherein
the sample is a sample provided without a pattern that is usable for positional alignment that cannot be observed.
5 . The microscope system according to claim 1 , wherein
the computer system calculates intersections between a shape of the image and a shape of the spot pattern, calculates a virtual shape of the spot pattern from the intersections, and calculates the position of the spot pattern from the virtual shape of a spot image.
6 . The microscope system according to claim 1 , wherein
the computer system is configured to
regarding the sample, acquire a plurality of images as the image while shifting a focus height by a predetermined unit amount,
plot a relation between the focus height and the spot position among images acquired by shifting by the unit amount in the plurality of images,
create a correlation formula based on the plot, and
calculate the amount of change in sample height based on the correlation formula.
7 . The microscope system according to claim 1 , further comprising:
an electron microscope, wherein
the computer system is configured to
refer to defect position information from an external optical inspection apparatus,
control the stage, the irradiation optical system and the observation optical system based on the defect position information, and move a target defect on the surface of the sample such that the target defect is positioned in a field of view of the observation optical system,
control the focus mechanism, set the focus height to a first focus height with respect to the target defect on the surface of the sample, and acquire the first image in a state of the first focus height,
control the focus mechanism, set the focus height to a second focus height with respect to the target defect on the surface of the sample, and acquire the second image in a state of the second focus height,
calculate the amount of change in sample height based on the first image and the second image,
control the focus mechanism and adjust the height positions of the focuses by using the amount of change in sample height, and
control the electron microscope and observe the target defect on the surface of the sample at the adjusted height positions of the focuses.
8 . The microscope system according to claim 7 , wherein
the irradiation optical system is a dark field optical system that radiates laser light as the light.
9 . The microscope system according to claim 8 , wherein
the sample is a sample provided without a pattern in which a pattern for positional alignment cannot be observed.
10 . The microscope system according to claim 8 , wherein
the computer system is configured to
refer to a focus map corresponding to the sample, and
when setting the focus height to the first focus height, set the focus height to a focus height according to a position on the focus map.