Charged-particle beam apparatus

1. A charged-particle beam apparatus for irradiating a sample disposed in a vacuum vessel with a charged particle beam released from a charged particle source, comprising:

a scanning deflector for scanning the charged particle beam on the sample;

a first light-generating surface for generating light based on a collision of charged particles released from a sample surface on a side of the charged particle source;

a light-guiding member for guiding the generated light to the outside of the vacuum vessel while maintaining the generation distribution of the light generated on the first light-generating surface;

a photodetector for detecting the light guided by the light-guiding member to the outside of the vacuum vessel; and

a light-transmission restricting member for restricting transmission of the light guided by the light-guiding member between the photodetector and the light-guiding member; and

a control device for controlling at least one of a size, a position, a shape, and a direction of a light transmission opening of the light-transmission restricting member;

wherein the control device adjusts at least one of the size, the position, the shape, and the direction of the light transmission opening such that a ratio of a signal of a first part on the sample and a signal of a second part different from the first part satisfies a predetermined condition, the ratio being obtained based on the scanning of the charged particle beam.

2. The charged-particle beam apparatus of claim 1 , wherein

the light-transmission restricting member is an opening plate having two or more openings which are different from each other in terms of at least one of the size, the position, the shape, and the direction, and includes a driving mechanism for driving the opening plate.

3. The charged-particle beam apparatus of claim 1 , wherein

the light-transmission restricting member is configured with a combination of a plurality of blades and is configured such that the size of the opening can be adjusted by adjusting the plurality of blades.

4. The charged-particle beam apparatus of claim 1 , wherein

the light-transmission restricting member is a liquid crystal plate and is configured such that at least one of the size, the position, the shape, and the direction of an opening through which the light is transmitted is variable by switching a liquid crystal orientation.

5. The charged-particle beam apparatus of claim 1 , wherein

the light-guiding member is configured with an optical fiber bundle.

6. The charged-particle beam apparatus of claim 1 , wherein

the light-guiding member includes an optical lens which allows the light at each position of the light-generating surface to be projected onto the photodetector.

7. The charged-particle beam apparatus of claim 1 , wherein

the first light-generating surface is disposed outside an axis of the charged particle beam, and the charged-particle beam apparatus includes a deflector for deflecting charged particles released from a sample toward the first light-generating surface disposed outside of the axis of the charged particle beam.

8. The charged-particle beam apparatus of claim 7 , further comprising:

a second light-generating surface for generating the light nearer to the sample than the deflector, based on the collision of the charged particles released from the sample.

9. The charged-particle beam apparatus of claim 8 , wherein

the second light-generating surface has a shape of a ring, and the charged particle beam is transmitted through a hole of the shape of a ring.

10. The charged-particle beam apparatus of claim 1 , wherein

the control device adjusts at least one of the size, the position, the shape, and the direction of the light transmission opening such that the ratio of the signal of the first part and the signal of the second part becomes equal to or greater than a predetermined value or becomes the maximum value.

11. A method for irradiating a sample disposed in a vacuum vessel with a charged particle beam released from a charged particle source, the method comprising:

irradiating the sample with the charged particle beam via a scanning deflector;

generating light from a first light-generating surface based on a collision of charged particles released from a sample surface on a side of the charged particle source;

guiding the light to outside of the vacuum vessel by a light-guiding member while maintaining a generation distribution of the light generated from the first light-generating surface;

detecting, by a photodetector, the light guided by the light-guiding member to the outside of the vacuum vessel;

restricting transmission of the light guided by the light-guiding member between the photodetector and the light-guiding member by a light-transmission restricting member; and

adjusting at least one of a size, a position, a shape, and a direction of a light transmission opening of the light-transmission restricting member such that a ratio of a signal of a first part on the sample and a signal of a second part different from the first part satisfies a predetermined condition, the ratio being obtained based on scanning of the charged particle beam.