Charged particle beam device
In order to improve a yield of light generated by a collision between secondary electrons and gas molecules, the invention provides a charged particle beam device including: a charged particle beam source configured to irradiate a sample with a charged particle beam; a sample chamber configured to hold the sample and a gas molecule; a positive electrode configured to form an electric field that accelerates a secondary electron emitted from the sample; a photodetector configured to detect light generated by a collision between the accelerated secondary electron and the gas molecule; and a light condensing unit disposed between the sample and the photodetector, having a light emitting space in which the light is generated, and configured to condense the light generated in the light emitting space on a photodetector side.
1. A charged particle beam device, comprising:
a charged particle beam source configured to irradiate a sample with a charged particle beam;
a sample chamber configured to hold the sample and a gas molecule;
a positive electrode configured to form an electric field that accelerates a secondary electron emitted from the sample;
a photodetector configured to detect light generated by a collision between the accelerated secondary electron and the gas molecule; and
a light condensing unit disposed between the sample and the photodetector, having a light emitting space in which the light is generated, and configured to condense the light generated in the light emitting space on a photodetector side.
2. The charged particle beam device according to claim 1 , wherein
a material of the light condensing unit is a fluorine-based resin.
3. The charged particle beam device according to claim 2 , wherein
the fluorine-based resin is polytetrafluoroethylene or expanded polytetrafluoroethylene having an amorphous crystal structure in part.
4. The charged particle beam device according to claim 3 , wherein
the light condensing unit has a thickness so that a diffuse reflectance is 80% or more at a wavelength of light of 300 nm to 450 nm.
5. The charged particle beam device according to claim 1 , wherein
a surface of the light condensing unit facing the light emitting space has a curved shape.
6. The charged particle beam device according to claim 5 , wherein
an inclination angle of the curved shape with respect to a central axis of the light condensing unit increases as a distance from the photodetector increases.
7. The charged particle beam device according to claim 1 , wherein
a surface of the light condensing unit facing the light emitting space has a sawtooth wave shape.
8. The charged particle beam device according to claim 7 , wherein
the sawtooth wave shape includes an inclined surface that is inclined with respect to a central axis of the light condensing unit and faces a photodetector side, and an orthogonal plane orthogonal to the central axis.
9. The charged particle beam device according to claim 1 , wherein
the condensing unit includes a light condensing unit base material, and a light scattering body or a phosphor is applied to an inner peripheral surface of the light condensing unit base material.
10. The charged particle beam device according to claim 1 , wherein
the light condensing unit is a glass member having a refractive index higher than that of vacuum in a wavelength region of the light and having a mirror surface on a surface thereof.
11. The charged particle beam device according to claim 10 , wherein
a metal coating is applied to an outer surface of the glass member.
12. The charged particle beam device according to claim 10 , further comprising:
a light guide in front of the photodetector, wherein
the light guide is a component integral with the glass member.
13. The charged particle beam device according to claim 1 , further comprising:
a second positive electrode to which a voltage lower than a voltage applied to the positive electrode is applied, wherein
the light condensing unit is provided inside the second positive electrode.
14. The charged particle beam device according to claim 1 , wherein
the light condensing unit is electrically insulated from the positive electrode.