Charged particle beam apparatus

1. A charged particle beam device comprising:

a charged particle source that generates a charged particle beam;

a focus adjustment unit that adjusts a focal position of the charged particle beam;

a deflection unit configured to scan the charged particle beam on a sample;

a detection unit that detects charged particles generated when the sample is irradiated with the charged particle beam;

a detected charged particle selection unit that selects charged particles to be detected by the detection unit; and

a control processing unit comprising a filter control unit operably coupled to and which controls the detected charged particle selection unit,

wherein the control processing unit is configured to perform focus adjustment of the focus adjustment unit, and is configured to perform reference adjustment of the detected charged particle selection unit by calculating and outputting a reference voltage to the filter control unit, based on information received from the detection unit acquired from one scan.

2. The charged particle beam device according to claim 1 , wherein the control processing unit is configured to:

calculate a focal evaluation value and brightness from an image generated based on the information from the detection unit,

calculate intensity of the focus adjustment unit by using the focal evaluation value, and

calculate reference intensity of the detected charged particle selection unit by using the brightness.

3. The charged particle beam device according to claim 2 , wherein:

the focus adjustment unit is an objective lens, and

the control processing unit calculates intensity of the objective lens from relationship between the intensity of the objective lens and the focal evaluation value.

4. The charged particle beam device according to claim 2 , wherein the control processing unit calculates the reference intensity of the detected charged particle selection unit from relationship between the intensity of the detected charged particle selection unit and the brightness.

5. The charged particle beam device according to claim 2 , wherein:

the focus adjustment unit is a retarding voltage control unit that applies retarding voltage to the sample, and

the control processing unit calculates the reference intensity of the detected charged particle selection unit from relationship among the intensity of the detected charged particle selection unit, intensity of the retarding voltage and the brightness.

6. The charged particle beam device according to claim 5 , wherein the control processing unit is configured to:

calculate the intensity of the retarding voltage from relationship between the retarding voltage and the focal evaluation value, and

calculate the reference intensity of the detected charged particle selection unit by using the calculated intensity of the retarding voltage.

7. The charged particle beam device according to claim 2 , wherein the control processing unit is configured to:

correct relationship between the intensity of the detected charged particle selection unit and the brightness by using a correction formula obtained from relationship between a change in the intensity of the focus adjustment unit and a change in the brightness, and

calculate the reference intensity of the detected charged particle selection unit from the corrected relationship between the intensity of the detected charged particle selection unit and the brightness.

8. The charged particle beam device according to claim 7 , wherein:

the detection unit includes a first detector having the detected charged particle selection unit and a second detector not having the detected charged particle selection unit, and

the control processing unit updates the correction formula by calculating the brightness and the focal evaluation value from an image generated based on information from the second detector.

9. The charged particle beam device according to claim 2 , further comprising:

a monitor unit that monitors an electric current amount of the charged particle beam;

a dose amount monitor unit that calculates a dose amount from the electric current amount and the number of times of the scan; and

a surface potential prediction unit that predicts a change in sample electrification potential with respect to the dose amount based on a deviation in the reference intensity with respect to the dose amount.

10. The charged particle beam device according to claim 2 , wherein the control processing unit corrects the brightness according to an image shift amount for adjustment of a position of the charged particle beam.

11. The charged particle beam device according to claim 1 , wherein:

the detection unit includes a first detector having the detected charged particle selection unit and a second detector not having the detected charged particle selection unit, and

the control processing unit generates a first image, generated based on information from the first detector, and a second image, generated based on information from the second detector, from the one scan.

12. The charged particle beam device according to claim 11 , wherein the control processing unit is configured to:

calculate brightness from the first image,

calculate a focal evaluation value from the second image,

calculate intensity of the focus adjustment unit by using the focal evaluation value, and

calculate reference intensity of the detected charged particle selection unit by using the brightness.

13. The charged particle beam device according to claim 11 , wherein the control processing unit is configured to:

calculate brightness from the first image,

calculate a displacement from the second image,

perform image shift control or stage control based on the displacement, and

calculate a sample potential change amount based on relationship between intensity of the detected charged particle selection unit and the brightness.

14. The charged particle beam device according to claim 11 , wherein the number of frames of the first image and the number of frames of the second image differ from each other.

15. The charged particle beam device according to claim 14 , wherein:

the number of frames of the second image is greater than the number of frames of the first image, and

the control processing unit makes the reference adjustment of the detected charged particle selection unit while one focus adjustment is made.