Method and apparatus for improving critical dimension variation
A method is described. The method includes obtaining a relationship between a thickness of a contamination layer formed on a mask and an amount of compensation energy to remove the contamination layer, obtaining a first thickness of a first contamination layer formed on the mask from a thickness measuring device, and applying first compensation energy calculated from the relationship to a light directed to the mask.
1. A method, comprising:
obtaining a relationship between thicknesses of a contamination layer formed on a mask and amounts of compensation energy to remove the contamination layer;
obtaining a first thickness of a first contamination layer formed on the mask from a thickness measuring device; and
removing the first contamination layer by applying first amounts of compensation energy calculated from the relationship to a first light directed to the mask, wherein each amount of compensation energy of the first amounts of compensation energy is less than a previous amount of compensation energy of the first amounts of compensation energy.
2. The method of claim 1 , further comprising measuring the first thickness of the first contamination layer by the thickness measuring device.
3. The method of claim 2 , wherein the measuring the first thickness of the first contamination layer is performed in a processing apparatus.
4. The method of claim 2 , wherein the measuring the first thickness of the first contamination layer is performed in a mask storage.
5. The method of claim 1 , further comprising forming a second contamination layer on the mask after applying the first amounts of compensation energy, wherein the second contamination layer is formed while the mask is idle for a period of time.
6. The method of claim 5 , wherein the period of time is greater than about eight hours.
7. The method of claim 5 , wherein the mask is disposed in a lithography system while being idle.
8. The method of claim 7 , further comprising applying second amounts of compensation energy calculated from the relationship to a second light directed to the mask.
9. The method of claim 8 , wherein the second contamination layer is removed by the second amounts of compensation energy.
10. A lithography process, comprising:
performing the lithography process in a lithography system, the lithography system comprising:
a first light source;
a mask stage;
a substrate stage;
a thickness measuring device configured to measure a thickness of a contamination layer formed on a mask to be disposed on the mask stage; and
a controller configured to control the first light source to emit a light with gradually decreasing amounts of compensation energy to remove the contamination layer while performing the lithography process.
11. The lithography process of claim 10 , wherein the thickness measuring device comprises a second light source and a detector.
12. The lithography process of claim 11 , further comprising:
an illuminator disposed between the first light source and the mask stage; and
a projection optics box disposed between the mask stage and the substrate stage.
13. The lithography process of claim 10 , wherein the mask stage and the substrate stage are disposed in a lithography chamber, and the first light source and the thickness measuring device are disposed in a device chamber adjacent the lithography chamber.
14. The lithography process of claim 13 , further comprising a transferring module and a transportation stage, wherein the transportation stage is disposed between the transferring module and the lithography chamber.
15. The lithography process of claim 13 , further comprising a shaft coupled to the mask stage, wherein the shaft is configured to tilt the mask stage with respect to a plane substantially parallel to a top surface of the substrate stage.
16. The lithography process of claim 10 , wherein the lithography process is an extreme ultraviolet lithography process.
17. A lithography system, comprising:
a light source configured to expose a photoresist layer;
a mask stage;
a substrate stage;
a mask storage, comprising:
a plurality of storage units; and
a first thickness measuring device configured to measure a thickness of a contamination layer formed on a mask to be disposed in the mask storage; and
a controller configured to control the light source to emit a light with gradually decreasing amounts of compensation energy to remove the contamination layer.
18. The lithography system of claim 17 , further comprising:
an illuminator disposed between the light source and the mask stage; and
a projection optics box disposed between the mask stage and the substrate stage.
19. The lithography system of claim 18 , wherein the mask stage and the substrate stage are disposed in a lithography chamber, and the light source is disposed in a device chamber adjacent the lithography chamber.
20. The lithography system of claim 19 , further comprising a second thickness measuring device disposed in the device chamber, wherein the second thickness measuring device is electrically connected to the controller.