Systems and methods for charged particle flooding to enhance voltage contrast defect signal
Systems and methods for implementing charged particle flooding in a charged particle beam apparatus are disclosed. According to certain embodiments, a charged particle beam system includes a charged particle source and a controller which controls the charged particle beam system to emit a charged particle beam in a first mode where the beam is defocused and a second mode where the beam is focused on a surface of a sample.
1. A charged particle beam system comprising:
a charged particle source configured to emit a charged particle beam along an optical axis;
an adjustable aperture configured to allow the charged particle beam to pass therethrough, the adjustable aperture being changeable to provide a selected aperture size; and
a controller configured to:
control the charged particle beam system to emit the charged particle beam in a first mode in which the charged particle beam passes through the adjustable aperture at a first aperture size and is incident on a sample at a first current level and the charged particle beam incident on the sample is defocused so as to flood a region on a surface of the sample with charged particles of the charged particle beam;
control the charged particle beam system to emit the charged particle beam in a second mode in which the charged particle beam passes through the adjustable aperture at a second aperture size and is incident on the sample at a second current level and the charged particle beam incident on the sample is focused to the surface of the sample; and
switch the charged particle beam system between the first mode and the second mode.
2. The charged particle beam system of claim 1 , wherein the controller is further configured to:
form a first spot on the surface of the sample in the first mode; and
form a second spot on the surface of the sample in the second mode, wherein a spot size of the first spot is different from the second spot.
3. The charged particle beam system of claim 1 , wherein the first current level is greater than or equal to the second current level.
4. The charged particle beam system of claim 1 , wherein the first current level is larger than the second current level.
5. The charged particle beam system of claim 2 , wherein the first spot is more defocused than the second spot.
6. The charged particle beam system of claim 2 , wherein the controller is further configured to:
form the first spot having a first spot size, and
form the second spot having a second spot size, wherein the first spot size is larger than the second spot size.
7. The charged particle beam system of claim 1 , wherein the controller is further configured to:
perform charged particle beam inspection of the sample in the second mode.
8. The charged particle beam system of claim 1 , further comprising:
an aperture plate having a first aperture and a second aperture formed thereon, wherein the first aperture has a size larger than that of the second aperture; and
a motor configured to adjust a position of the aperture plate;
wherein the controller is configured to:
move the aperture plate so that the first aperture is aligned with the optical axis in the first mode, and
move the aperture plate so that the second aperture is aligned with the optical axis in the second mode.
9. The charged particle beam system of claim 1 , wherein the charged particle beam system is a scanning electron microscope and the charged particle beam is an electron beam.
10. A method of inspecting a sample using a charged particle beam system, the method comprising:
emitting a charged particle beam through an adjustable aperture plate at a first aperture size so that the charged particle beam is incident on the sample at a first current level, the charged particle beam being defocused on a surface of the sample so as to flood a region on the surface of the sample with charged particles of the charged particle beam; and
emitting a charged particle beam through the adjustable aperture plate at a second aperture size so that the charged particle beam is incident on the sample at a second current level, the charged particle beam being focused on the surface of the sample.
11. The method of claim 10 , further comprising:
adjusting the adjustable aperture such that the second current level is smaller than the first current level.
12. The method of claim 10 , further comprising:
performing charged particle beam inspection of the sample.
13. The method of claim 10 , further comprising:
forming a first spot on a surface of the sample at the first current level; and
forming a second spot on the surface of the sample at the second current level, wherein a spot size of the first spot is different from the second spot.
14. The method of claim 10 , wherein the second current level is smaller than the first current level.
15. The method of claim 13 , wherein the second spot is smaller than the first spot.
16. The charged particle beam system of claim 1 , further comprising a column aperture, wherein the controller is configured to focus the charged particle beam in a region of the column aperture in the first mode.
17. The charged particle beam system of claim 16 , wherein the controller is configured to project the charged particle beam on the column aperture in the second mode.
18. The method of claim 10 , further comprising focusing the charged particle beam in a region of a column aperture while performing charged particle flooding.
19. The method of claim 18 , further comprising projecting the charged particle beam on the column aperture.