Discharging method for charged particle beam imaging
A layer of conductive or semi-conductive material is formed on a surface of a sample and then the sample, when being charged particle beam imaged, is electrically coupled with an object having a large charge-receiving or charge-storage capacity (e.g., capacitance). Hence, the charging on the sample surface is removed and released quickly by the layer. The layer is then removed by reacting it with a predefined agent. The reaction forms a gaseous product which does not form a physical or chemical bond to the sample surface.
1. A method for reversibly enhancing dispersion of charge from a sample for charged particle beam inspection, comprising:
transferring said sample from a standard machine interface pod (SMIF) to a spin coater;
spin coating a conductive layer on a sample surface of said sample;
transferring said sample from the spin coater to a load lock of a scanning electron microscope system;
forming a vacuum around said sample;
transferring said sample to an electrically grounded rack in a main inspection chamber so that the conductive layer contacts the electrically grounded rack;
inspecting said sample on said electrically grounded rack with charged particle beam inspection;
transferring said sample from the electrically grounded rack to the load lock;
generating a high energy plasma with a plasma generator in the load lock;
introducing a first gaseous agent into the load lock;
pretreating the first gaseous agent with the high energy plasma to create an activated gaseous agent in the load lock; and
exposing the conductive layer to the activated gaseous agent in the load lock until all of the conductive layer reacts to form reaction gases.
2. The method of claim 1 , wherein said conductive layer comprises carbon, graphite, carbon-nano tube, carbon powder, carbon nano-ribbon, or carbon black.
3. The method of claim 1 , wherein the thickness of the said conductive layer is equal to or greater than 10 angstroms (Å).
4. The method of claim 1 , wherein said first gaseous agent comprises gaseous oxygen or air.
5. The method of claim 1 , wherein said transferring said sample to said electrically grounded rack is performed using a robotic arm.
6. The method of claim 1 , wherein said transferring said sample from said electrically grounded rack to said load lock is performed using a robotic arm.
7. The method of claim 1 , wherein said sample is made of substantially insulative materials.
8. The method of claim 1 , further comprising exhausting said reaction gases from said load lock.
9. The method of claim 1 , wherein said sample is a mask for lithography.
10. The method of claim 1 , wherein the thickness of said conductive layer is greater than 10 angstroms (Å) and less than 200 angstroms (Å).
11. A method for reversibly enhancing dispersion of charge from a sample for charged particle beam inspection, comprising:
forming a conductive layer of conductive or semi-conductive material on a sample surface of said sample wherein said conductive material is able to react with a gaseous agent to form at least one gas molecule which does not form physical or chemical bonding to said sample surface;
electrically coupling said conductive layer through an electrically grounded rack, during charged particle beam inspection, with an object having a large capacitance through said layer; and
introducing said gaseous agent into a load lock after charged particle beam inspection to react with said conductive layer until all of said conductive layer is fully reacted.
12. The method of claim 11 , wherein said material comprises carbon, graphite, carbon-nano tube, carbon powder, carbon nano-ribbon, carbon black, or any combination thereof.
13. The method of claim 11 , wherein the thickness of said conductive layer is greater than 10 angstroms (Å) and less than 200 angstroms (Å).
14. The method of claim 11 , wherein said agent comprises gaseous oxygen, air, or compressed air.
15. The method of claim 11 , wherein said gaseous agent is in the form of atoms, ions, or radicals.
16. The method of claim 11 , wherein said conductive layer is formed on said sample surface by spin coating.
17. The method of claim 11 , wherein said sample is made of substantially insulative materials.
18. The method of claim 11 , wherein said agent is pretreated with a high energy particle or irradiation.
19. The method of claim 11 , wherein said sample is a mask for lithography.
20. The method of claim 1 , wherein the thickness of said conductive layer is greater than 10 angstroms (Å) and less than 100 angstroms (Å).