Charged particle beam apparatus
A charged particle beam apparatus having an aberration correction capability at high acceleration voltages. The charged particle beam apparatus comprises a charged particle beam source; an extraction electrode to extract charged particles from the charged particle beam source; a charged particle beam gun including a means for converging a charged particle beam; an acceleration means for accelerating a charged particle beam emitted from the charged particle beam gun; and an aberration correction means disposed between the charged particle beam gun and the acceleration means, in which an aberration enough to cancel out an aberration of a charged particle beam on the specimen surface is provided to an extraction electrical potential or an equivalent beam at the initial acceleration stage.
1. A charged particle beam apparatus which irradiates a specimen with a charged particle beam including:
a charged particle gun which emits the charged particle beam; and
a charged particle optical system which directs the emitted charged particle beam to the specimen;
the charged particle gun further comprising:
means for generating the charged particle beam;
an aberration corrector which adds a reverse aberration correction to the charged particle beam so as to cancel an aberration caused in the charged particle optical system; and
an acceleration means for accelerating the charged particle beam to which the reverse-aberration correction has been added,
wherein the charged particle gun and the aberration corrector are integrally formed.
2. A charged particle beam apparatus according claim 1 , wherein the aberration corrector enables correction of at least one of chromatic aberration and spherical aberration.
3. A charged particle beam apparatus according to claim 1 , further comprising a valve disposed between the charged particle gun and the charged particle optical system so as to open and close an aperture for passing the charged particle beam; and a means for activating the valve.
4. A charged particle beam apparatus according to claim 1 , wherein the acceleration means is a Butler type electrostatic lens.
5. A charged particle beam apparatus including a charged particle gun;
the charged particle gun comprising:
a charged particle beam source which generates a charged particle beam;
an extractor electrode which extracts the charged particle beam to outside of the charged particle beam source;
an aberration corrector which corrects aberration of the charged particle beam that has passed the extraction electrode; and
a Bulter type electrostatic lens which accelerates the charged particle beam that passed the aberration corrector;
wherein the Butler type electrostatic lens comprises an upper electrode formed on the bottom of the aberration corrector and a lower electrode disposed opposite to the upper electrode.
6. A charged particle beam apparatus according to claim 5 , wherein the upper and lower electrodes of the Butler type electrostatic lens each is tapered along the perimeter of an aperture through which the charged particle beam passes.
7. A charged particle beam apparatus according to claim 1 , wherein the aberration further comprises:
four stages of electrostatic quadrupole elements; and
two stages of magnetic quadrupole elements;
wherein the two stages of magnetic quadrupole elements generate a magnetic potential distribution similar to a rotated electrical potential distribution of the electrostatic quadrupole elements by 45 degrees with respect to an optical axis of the charged particle beam.
8. A charged particle beam apparatus according to claim 7 , wherein the aberration corrector further comprises four stages of electrostatic octupole elements that apply an octupole electrical potential to the four stages of electrostatic quadrupole element.
9. A charged particle beam apparatus according to claim 1 , the aberration corrector further comprises:
four stages of electrostatic quadrupole elements; and
four stages of electrostatic octupole elements that applies an octupole electrical potential to the four stages of electrostatic quadrupole element.
10. A charged particle beam apparatus according to claim 6 , wherein the tapered portion of the aperture is mirror-finished.