Charged particle beam device and arithmetic device
It is possible to determine an optimal parasitic aberration adjustment amount even when the relationship of the parasitic aberration adjustment amount with respect to the field intensity of multiple poles changes nonlinearly. To this end, in the present invention, an aberration correction amount is computed by measuring an aberration coefficient of an optical unit of a charged particle beam device, and at the same time, the present value of a power supply control value applied to an aberration corrector is measured. Then, the parasitic aberration adjustment amount for suppressing the amount of a parasitic aberration generated in the aberration corrector is computed on the basis of the aberration correction amount and the present value of the power supply control value.
1. A charged particle beam device comprising:
a charged particle source configured to emit a charged particle beam;
a condenser lens configured to converge the charged particle beam;
an aberration corrector having multiple stages of multiple poles and configured to correct an aberration of an optical unit;
an aberration corrector power supply configured to generate power to be applied to the multiple poles according to the power supply control value;
an aberration coefficients estimation unit configured to measure a plurality of aberration coefficients of the optical unit when the power supply control value is applied to the multiple poles from the aberration corrector power supply;
an aberration correction target estimation unit configured to select an aberration coefficient from the plurality of aberration coefficients;
an aberration correction amount estimation unit that determines a multipole control value, of a current or a voltage, to correct the selected aberration coefficient based on the selected aberration coefficient;
an aberration corrector power output value measurement unit configured to measure the present value of the power supply control value applied to the multiple poles from the aberration corrector power supply;
a parasitic aberration adjustment amount estimation unit that determines a parasitic aberration adjustment amount based on the measured value of the power supply control value applied to the multiple poles and the multipole control value to adjust an aberration resulting from applying power corresponding to the multipole control value to the aberration corrector; and
an arithmetic device configured to compute a power supply control value for aberration correction to be applied to the multiple poles by adding the multipole control value to the parasitic aberration adjustment amount together,
wherein the parasitic aberration adjustment amount estimation unit stores and holds data that indicates a correspondence between the multipole control value and the parasitic aberration adjustment amount that is necessary to adjust a parasitic dipole field or a parasitic quadrupole field generated when power corresponding to the multipole control value is applied to the aberration corrector.
2. The charged particle beam device according to claim 1 , wherein the parasitic aberration adjustment amount is for adjusting a parasitic dipole field or a parasitic quadrupole field generated due to an electrical and/or mechanical deviation of the aberration corrector.
3. The charged particle beam device according to claim 1 , wherein the parasitic aberration adjustment amount estimation unit determines a function that is approximate to the correspondence in a range around the measured value of the power supply control value, and computes the parasitic aberration adjustment amount in accordance with the function.
4. The charged particle beam device according to claim 1 , wherein the multiple poles in each of the multiple stages generate a non-rotationally symmetrical electric field and/or magnetic field.
5. The charged particle beam device according to claim 1 ,
wherein the aberration correction amount estimation unit determines the multipole control value on the basis of an aberration coefficient measured for the optical unit before a power supply control value for aberration correction is applied to the multiple poles from the aberration corrector power supply.
6. A charged particle beam device comprising:
a charged particle source configured to emit a charged particle beam;
a condenser lens configured to converge the charged particle beam;
an aberration corrector having multiple stages of multiple poles and configured to correct an aberration of an optical unit;
an aberration corrector power supply configured to generate power to be applied to the multiple poles according to the power supply control value;
an aberration coefficients estimation unit configured to measure a plurality of aberration coefficients of the optical unit when the power supply control value is applied to the multiple poles from the aberration corrector power supply;
an aberration coefficients measurement result memory unit configured to record and store a measurement history of the aberration coefficients;
an aberration correction target estimation unit configured to select an aberration coefficient from the plurality of aberration coefficients;
an aberration correction amount estimation unit that determines a multipole control value, of a current or a voltage, to correct the selected aberration coefficient based on the selected aberration coefficient;
an aberration corrector power output value measurement unit configured to measure a present value of the power supply control value applied to the multiple poles from the aberration corrector power supply;
an aberration corrector power output value memory unit configured to record and store a measurement history of the power supply control value;
a parasitic aberration adjustment amount estimation unit configured to compute a parasitic aberration adjustment amount based on the measurement history of the aberration coefficient, the measurement history of the power supply control value, and the multipole control value, to adjust an aberration resulting from applying power corresponding to the multipole control value to the aberration corrector; and
an arithmetic device configured to compute, by adding the multipole control value and the parasitic aberration adjustment amount together, a power supply control value for aberration correction to be applied to the multiple poles.
7. The charged particle beam device according to claim 6 , wherein the parasitic aberration adjustment amount estimation unit computes the parasitic aberration adjustment amount on the basis of:
(1) the multipole control value,
(2) a magnitude of a parasitic dipole field or a parasitic quadrupole field that remain in the optical unit,
(3) an amount of change of the power supply control value, which is applied to a field of the multiple poles to be adjusted next, from the power supply control value that was changed last time, and
(4) an amount of change of the parasitic dipole field or the parasitic quadrupole field that occurred, when the power supply control value applied to the field of the multiple poles to be adjusted next, was changed last time.
8. The charged particle beam device according to claim 6 , wherein the multiple poles in each of the multiple stages generate a non-rotationally symmetrical electric field and/or magnetic field.
9. The charged particle beam device according to claim 6 , wherein the arithmetic device displays an execution status of aberration correction on a screen.
10. The charged particle beam device according to claim 6 ,
wherein the aberration correction amount estimation unit determines the multipole control value on the basis of an aberration coefficient measured for the optical unit before a power supply control value for aberration correction is applied to the multiple poles from the aberration corrector power supply.