Patent ID: 8618480

Claim:
A charged particle beam apparatus, comprising: a charged particle source, which emits primary charged particles along a direction, wherein said direction is an optical axis of said charged particle beam apparatus and said primary charged particles form a primary charged particle beam; an accelerating electrode, which is located below said charged particle source and comprises a first beam-passing opening aligned with said optical axis for said primary charged particle beam passing through, wherein said charged particle source and said accelerating electrode are excited to generate an accelerating field therebetween to accelerate said primary charged particles; a first selectable beam-limit aperture plate, which is located below said accelerating electrode and comprises a first plurality of beam-limit openings, wherein one of said first plurality of beam-limit openings in use is aligned with said optical axis and limits a current of said primary charged particle beam to a first current value; a magnetic condenser lens, which is located below said first selectable beam-limit aperture plate and aligned with said optical axis; a magnetic objective lens, which is located below said magnetic condenser lens and aligned with said optical axis; a retarding electrode, which is located inside or below said magnetic objective lens and comprises a second beam-passing opening aligned with said optical axis for said primary charged particle beam passing through; a sample stage, which is located below said retarding electrode and supports a sample, wherein said retarding electrode and said sample are electrically excited to generate a retarding field therebetween so that primary charged particles are decelerated to land on a surface of said sample with kinetic energies lower than 5 keV, wherein said magnetic condenser lens and said magnetic objective lens focus said primary charged particle beam to forms a focused probe spot onto said surface of said sample; a deflection unit, which is above said sample and deflects said primary charged particle beam so as to make said focused probe spot scan said surface of said sample; and a first charged-particle detector, which is located above said deflection unit, comprises a third beam-passing opening aligned with said optical axis for said primary charged particle beam passing through and a first detection area opposite to said surface of said sample so as to collect secondary charged particles emitted from said scanned surface of said sample.