Charged particle gun and charged particle beam device
The present disclosure provides a charged particle beam device capable of simultaneously achieving protection of a charged particle source against electrical discharging inside a charged particle gun and highly accurate control of the charged particle gun, for both DC and AC components. A charged particle gun according to the present disclosure is configured such that an extraction voltage and an acceleration voltage are superposed and supplied to a charged particle beam source, a wiring between the charged particle beam source and a voltage circuit is covered with first and second enclosures, the first enclosure is configured to be connected to an extraction electrode, and the second enclosure is configured to be connected to an acceleration electrode and to a reference voltage of the voltage circuit.
1. A charged particle gun configured to irradiate a sample with a charged particle beam, the charged particle gun comprising:
a charged particle beam source configured to emit the charged particle beam;
a voltage circuit configured to supply a voltage to the charged particle beam source;
a wiring configured to connect the charged particle beam source and the voltage circuit;
a cover portion configured to cover the wiring;
an extraction electrode configured to extract the charged particle beam from the charged particle beam source; and
an acceleration electrode configured to accelerate the charged particle beam, wherein
the voltage circuit includes a first voltage source and a second voltage source,
the first voltage source and the second voltage source are disposed to output to the wiring an addition voltage obtained by adding an output voltage from the first voltage source to an output voltage from the second voltage source,
the cover portion includes a first enclosure and a second enclosure,
the first enclosure is configured to be connected to the extraction electrode and to an output terminal of the second voltage source, and
the second enclosure is configured to be connected to the acceleration electrode and to a reference voltage of the voltage circuit.
2. The charged particle gun according to claim 1 , wherein
the voltage circuit includes a first feedback control circuit configured to feedback-control the first voltage source according to a current fed back from the extraction electrode to the first voltage source via the first enclosure, and
the first feedback control circuit is housed in the first enclosure.
3. The charged particle gun according to claim 1 , wherein
the voltage circuit includes a second feedback control circuit configured to feedback-control the second voltage source according to a current fed back from the acceleration electrode to the second voltage source via the second enclosure, and
the second feedback control circuit is housed in the second enclosure.
4. The charged particle gun according to claim 1 , wherein
the first enclosure is configured such that a voltage distribution of the first enclosure covers the wiring and the first voltage source.
5. The charged particle gun according to claim 1 , wherein
the second enclosure is configured such that a voltage distribution of the second enclosure covers the voltage distribution of the first enclosure.
6. The charged particle gun according to claim 1 , wherein
the voltage circuit includes a first output resistor connected between an output terminal of the first voltage source and the wiring, and
the first voltage source outputs a current to the wiring via the first output resistor.
7. The charged particle gun according to claim 1 , wherein
the voltage circuit includes a second output resistor connected between the first voltage source and the second voltage source, and
the second voltage source outputs a current to the first enclosure via the second output resistor.
8. The charged particle gun according to claim 6 , wherein
the first output resistor and a stray capacitance between the wiring and the first enclosure act as a low-pass filter configured to reduce an AC component of an output voltage output by the first voltage source.
9. The charged particle gun according to claim 7 , wherein
the second output resistor and a stray capacitance between the first enclosure and the second enclosure act as a low-pass filter configured to reduce an AC component of an output voltage output by the second voltage source.
10. The charged particle gun according to claim 2 , wherein
the voltage circuit includes a first output resistor connected between an output terminal of the first voltage source and the wiring,
the first voltage source outputs a current to the wiring via the first output resistor, and
the first feedback control circuit feedback-controls the first voltage source such that the first voltage source outputs a voltage obtained by adding a voltage drop due to the first output resistor to a set value of an extraction voltage applied to the extraction electrode.
11. The charged particle gun according to claim 3 , wherein
the voltage circuit includes a second output resistor connected between the first voltage source and the second voltage source,
the second voltage source outputs a current to the first enclosure via the second output resistor, and
the second feedback control circuit feedback-controls the second voltage source such that the second voltage source outputs a voltage obtained by subtracting a set value of an extraction voltage applied to the extraction electrode from a set value of an acceleration voltage applied to the charged particle beam source, and further adding a voltage drop due to the second output resistor.
12. The charged particle gun according to claim 1 , further comprising:
a current source configured to clean or heat the charged particle beam source, wherein
the current source is housed in the first enclosure.
13. The charged particle gun according to claim 1 , further comprising:
a suppressor electrode configured to restrain thermal electrons generated from the charged particle beam source;
a suppressor voltage source configured to supply a voltage to the suppressor electrode; and
a circuit configured to control the suppressor voltage source according to an output current from the suppressor voltage source, wherein
the suppressor voltage source is housed in the first enclosure.
14. The charged particle gun according to claim 1 , further comprising:
a lens electrode constituting a lens configured to focus the charged particle beam with respect to the sample;
a lens voltage source configured to supply a voltage to the lens electrode; and
a circuit configured to control the lens voltage source according to an output current from the lens voltage source, wherein
the lens voltage source is located outside the first enclosure and inside the second enclosure.
15. A charged particle beam device comprising the charged particle gun according to claim 1 .