EUV wafer defect improvement and method of collecting nonconductive particles
View Patent ↗An EUV lithographic apparatus includes a wafer stage and a particle removing assembly for cleaning a wafer for an extreme ultraviolet (EUV) lithographic apparatus. The wafer stage includes a measurement side and an exposure side. The particle removing assembly includes particle removing electrodes, an exhaust device and turbomolecular pumps. The particle removing electrodes is configured to direct debris from the chamber by suppressing turbulence such that the debris can be exhausted from the wafer stage to the outside of the processing apparatus. In some embodiments, turbomolecular pumps are turned off in the measurement side of the wafer stage so that an exhaust flow can be guided to an exposure side of the wafer stage. In some embodiments, the speed of voltage rise to the electrodes of the wafer chuck is adjusted.
1. A method of processing a wafer in a vacuum chamber, the method comprising:
moving a wafer stage in the vacuum chamber;
generating a particle from the wafer stage;
applying a voltage to particle removing electrodes provided at two sides of the wafer stage so as to sandwich the wafer stage, thereby removing the particle, wherein the particle removing electrodes extend from a measurement side of the wafer stage to an exposure side of the wafer stage; and
turning off a pump at the measurement side of the wafer stage to guide an exhaust flow to the exposure side of the wafer stage.
2. The method of claim 1 , wherein the voltage is a DC voltage.
3. The method of claim 1 , wherein the voltage is an AC voltage.
4. The method of claim 3 , wherein the voltage is provided by a radio frequency (RF) power supply.
5. The method of claim 1 , wherein the voltage is supplied by pulses having a duty ratio.
6. The method of claim 5 , wherein the duty ratio is from 10% to 90%.
7. The method of claim 1 , wherein the particle is generated from a cable attached to the wafer stage.
8. The method of claim 1 , wherein the particle is non-electroconductive.
9. A method of cleaning a wafer in a vacuum chamber, comprising:
applying a voltage to a pair of particle removing electrodes of a removing assembly in the vacuum chamber,
wherein the pair of particle removing electrodes are provided at two opposite sides of a wafer stage in the vacuum chamber,
wherein the wafer stage is configured to hold the wafer and one side of the wafer stage is a measurement side and an opposing side of the wafer stage is an exposure side, and
wherein the pair of particle removing electrodes extend from the measurement side to the exposure side;
collecting particles generated by a movement of the wafer stage that fall on the wafer; and
turning off a pump at the measurement side of the wafer stage to guide an exhaust flow to the exposure side of the wafer stage.
10. The method of claim 9 , wherein the voltage is applied by a voltage source to the pair of particle removing electrodes.
11. The method of claim 10 , wherein the voltage source is a radio frequency (RF) power supply.
12. The method of claim 10 , wherein a controller coupled to the voltage source is configured to adjust at least one parameter selected from the group consisting of a voltage, a frequency, a duty ratio, and a rate of voltage change.
13. The method of claim 12 , further comprising detecting an amount of the particles on the wafer.
14. The method of claim 13 , wherein the controller applies the voltage to the pair of particle removing electrodes when the amount of the particles detected is detected greater than a threshold size.
15. The method of claim 9 , wherein additional electrodes are provided at corners of the vacuum chamber to collect the particles.
16. A method of processing a wafer in a vacuum chamber, comprising:
generating a movement of a wafer stage that holds a wafer in the vacuum chamber, wherein the wafer stage includes a measurement side and an exposure side;
generating an exhaust flow in the vacuum chamber; and
applying a voltage to a pair of particle removing electrodes of a removing assembly,
wherein the pair of particle removing electrodes are provided at two opposite sides of the wafer stage to sandwich the wafer stage, and extend from the measurement side to the exposure side;
collecting particles generated by the movement of the wafer stage that fall on the wafer; and
turning off a pump at the measurement side of the wafer stage to guide the exhaust flow to the exposure side of the wafer stage.
17. The method of claim 16 , wherein the particles are generated from a cable attached to the wafer stage.
18. The method of claim 16 , wherein the particles are non-electroconductive.
19. The method of claim 16 , further comprising performing a lithography process on the wafer using extreme ultraviolet (EUV) light.
20. The method of claim 16 , wherein the pump is a turbomolecular pump.