Scanning electron microscope with objective lens below sample stage
An immersion objective lens is configured below a stage such that multiple detectors can be configured above sample for large beam current application, particularly for defect inspection. Central pole piece of the immersion objective lens thus can be provided that a magnetic monopole-like field can be provided for electron beam. Auger electron detector thus can be configured to analyze materials of sample in the defect inspection.
1. A charged particle beam apparatus, comprising:
a charged particle source for providing a charged particle beam;
a condenser lens for condensing the charged particle beam;
a scanning unit for scanning the charged particle beam on a sample;
a stage including an electrostatic chuck for supporting the sample, a first mesa movable in a first direction, and a second mesa movable in a second direction, wherein the first direction is different from the second direction;
a detector system for receiving signal particles from the sample after the charged particle beam impinges on the sample; and
an objective lens, below said electrostatic chuck stage, including a central polepiece aligned to the charged particle beam for focusing the charged particle beam on the sample, wherein the central polepiece protrudes through the first mesa and the second mesa and is located below and adjacent to the electrostatic chuck.
2. The charged particle beam apparatus according to claim 1 , wherein the charged particle source provides an electron beam.
3. The charged particle beam apparatus according to claim 2 , wherein said stage is a maglev stage.
4. The charged particle beam apparatus according to claim 3 , wherein said maglev stage includes a first mesa movable along a first direction horizontally, a second mesa movable along a second direction horizontally perpendicular to the first direction, and an electrostatic chuck on the second mesa.
5. The charged particle beam apparatus according to claim 4 , wherein said first mesa and second mesa are vertically movable.
6. The charged particle beam apparatus according to claim 5 , wherein the central polepiece protrudes to the sample.
7. The charged particle beam apparatus according to claim 6 , wherein the signal particles includes secondary electrons (SE), backscattered electrons (BSE), and Auger electrons (AE).
8. The charged particle beam apparatus according to claim 7 , wherein said detector system includes a SE detector, a BSE detector, and an AE detector for receiving secondary electrons, backscattered electrons, and Auger electrons respectively.
9. The charged particle beam apparatus according to claim 8 , further comprising a booster inside the condenser lens to accelerate the electron beam.
10. The charged particle beam apparatus according to claim 9 , further comprising a retard electrode above the sample to retard the electron beam.
11. The charged particle beam apparatus according to claim 10 , further comprising a ferrite layer below said retard electrode to couple with a magnetic field generated by the objective lens.
12. The charged particle beam apparatus according to claim 11 , further comprising a first Wien filter for filtering the secondary electrons into said SE detector, and a second Wien filter for filtering the backscattered electrons into said BSE detector.
13. The charged particle beam apparatus according to claim 12 , further comprising a variable deflector around the central pole piece of the objective such that said objective lens is a variable axis lens.
14. The charged particle beam apparatus according to claim 13 , wherein the variable axis lens is a moving objective lens.
15. The charged particle beam apparatus according to claim 14 , further comprising a first deflector and a second deflector to move the electron beam along an axis of the moving objective lens.
16. The charged particle beam apparatus according to claim 13 , wherein the variable axis lens is a swing objective lens.
17. The charged particle beam apparatus according to claim 16 , further comprising a deflector to moving the electron beam along an axis of the swing objective lens.
18. An electron beam apparatus, comprising:
an electron source for providing an electron beam;
a condenser lens for condensing the electron beam;
a scanning unit for scanning the charged particle beam on a sample;
a first objective lens below said condenser lens for focusing the electron beam;
a maglev stage, below said first objective lens, including an electrostatic chuck for supporting the sample, a first mesa movable in a first direction, and a second mesa movable in a second direction, wherein the first direction is orthogonal to the second direction;
a detector system for receiving signal electrons from the sample after the electron beam impinges on the sample; and
a second objective lens, below said electrostatic chuck, including a central polepiece, aligned to the charged particle beam and protruding towards the sample, for focusing the electron beam on the sample, wherein the central polepiece protrudes through the first mesa and the second mesa and is located below and adjacent to the electrostatic chuck.
19. The electron beam apparatus according to claim 18 , further comprising a retard electrode above the sample to retard the electron beam.
20. The electron beam apparatus according to claim 19 , further comprising a ferrite layer below said retard electrode to couple with a magnetic field generated by the second objective lens.