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US 8,618,480 B2Granted
Charged particle beam apparatus
AssigneeHermes Microvision, Inc.
InventorsWeiming Ren, Xiaoli Guo, Xuedong Liu, Zhongwei Chen
Life of this patent
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Abstract
The present invention provides a charged particle beam apparatus which employs LVSEM to inspect sample surface with a throughput much higher than the prior art. The high throughput is realized by providing a probe current and a FOV both several times of those of the prior art. Accordingly several means are proposed to avoid obvious degradation of image resolution due to the increases in Coulomb effect and geometric aberrations, and increase efficiency and uniformity of secondary charged particle collection.
Claims29
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.
7 more elements
An electron beam apparatus, comprising:
- an electron source of field emission, which emits primary electrons along a direction, wherein said direction is an optical axis of said electron beam apparatus and said primary electrons form a primary electron beam;
- an accelerating electrode, which is located below said electron source and comprises a first beam-passing opening aligned with said optical axis and for said primary electron beam passing through, wherein said electron source and said accelerating electrode are excited to generate an accelerating field therebetween to accelerate said primary electrons;
- a fixed beam-limit aperture plate, which is below said accelerating electrode and comprises an initial beam-limit opening aligned with said optical axis, wherein said initial beam-limit opening limits a current of said primary electron beam to a first current value;
- a first selectable beam-limit aperture plate, which is located below said fixed beam-limit aperture plate 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 said primary electron beam to a second current value;
- a magnetic condenser lens, which is aligned with said optical axis and located below said first selectable beam-limit aperture plate and has a radial magnetic-circuit gap opposite to a lower surface thereof and configured to generate a magnetic field deeply immersing said electron source;
- a fixed aperture plate, which is below said magnetic condenser lens and comprise a protection opening aligned with said optical axis;
- a first electron detector, which is below said fixed aperture plate and comprises a third beam-passing opening aligned with said optical axis for said primary electron beam passing through, wherein said fixed aperture plate is configured to prevent said primary electrons from hitting said first electron detector;
- a magnetic objective lens, which is located below said first electron detector and aligned with said optical axis;
- a retarding electrode, which is located below or inside said magnetic objective lens and comprises a second beam-passing opening aligned with said optical axis for said primary electron 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 set at potentials to generate a retarding field therebetween so that primary electrons 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 electron beam to forms a focused probe spot onto said surface of said sample, wherein secondary electrons and backscattered electrons emerge from said sample surface where said primary electrons land on, thereby forming a secondary electron beam and a backscattered electron beam respectively;
- and
- a deflection unit, which is above said sample and comprises at least one electrostatic deflector and one of said at least one deflector is configured to generate an electrostatic deflection field superimposed onto a magnetic field of said magnetic objective lens along said optical axis so as to reduce off-axis aberrations due to a deflection, wherein said magnetic condenser lens, said magnetic objective lens, said retarding field and said deflection unit are configured so that said secondary electron beam and said backscattered electron beam respectively form no crossover on and below said first electron detector, and all or most of said secondary electrons are collected by said first electron detector.
9 more elements
An electron beam apparatus, comprising:
- an electron source of field emission, which emits primary electrons along a direction, wherein said direction is an optical axis of said electron beam apparatus and said primary electrons form a primary electron beam;
- a magnetic condenser lens aligned with said optical axis and located below said electron source, which has a radial magnetic-circuit gap opposite to said electron source and is configured to generate a magnetic field deeply immersing said electron source;
- an electron detector, which is below said magnetic condenser lens and comprises a first beam-passing opening aligned with said optical axis for said primary electron beam passing through;
- a magnetic objective lens, which is located below said electron detector and aligned with said optical axis;
- a sample stage, which is located below said magnetic objective lens and supports a sample, wherein said magnetic condenser lens and said magnetic objective lens focus said primary electron beam to form a focused probe spot onto said surface of said sample;
- and
- a deflection unit, which is above said sample and comprises at least one electrostatic deflector and one of said at least one deflector is configured to generate an electrostatic deflection field superimposed onto a magnetic field of said magnetic objective lens along said optical axis so as to reduce off-axis aberrations due to a deflection, wherein all or most of secondary electrons emitted from the sample surface are collected by said electron detector.
4 more elements
Dependencies are inferred from the claim text.