Immersion post-exposure bake lithography process and systems
A method of performing extreme ultraviolet lithography process includes applying a protic solvent over an extreme ultraviolet (EUV) photoresist layer located over a substrate after exposure to EUV radiation, heating the protic solvent on the EUV photoresist layer to a post-exposure bake temperature photoresist, and removing the protic solvent from above the EUV photoresist layer prior to developing the EUV photoresist layer.
1. A method of performing extreme ultraviolet lithography process, comprising:
applying a protic solvent over an extreme ultraviolet (EUV) photoresist layer located over a substrate after exposure to EUV radiation;
heating the protic solvent on the EUV photoresist layer to a post-exposure bake temperature while the EUV photoresist layer is immersed in the protic solvent or while the protic solvent is present over the EUV photoresist layer as a puddle; and
removing the protic solvent from above the EUV photoresist layer prior to developing the EUV photoresist layer.
2. The method of claim 1 , wherein the protic solvent permeates the EUV photoresist layer during heating of the EUV photoresist layer to provide protons for accelerating a deprotection reaction for EUV irradiated portions of the EUV photoresist layer.
3. The method of claim 1 , wherein the protic solvent is selected from water, acetic acid, formic acid, nitromethane, methanol, ethanol, propanol, isopropanol, or n-butanol.
4. The method of claim 1 , wherein heating the protic solvent on the EUV photoresist layer to the post-exposure bake temperature comprises heating the protic solvent to a boiling point of the protic solvent at 1 atmospheric pressure.
5. The method of claim 1 , wherein heating the protic solvent on the EUV photoresist layer to the post-exposure bake temperature comprises pressurizing the protic solvent on the EUV photoresist layer to a post-exposure bake pressure, and wherein the post-exposure bake temperature is less than or equal to a boiling temperature of the protic solvent at the post-exposure bake pressure.
6. The method of claim 5 , wherein:
the post-exposure bake pressure is in a range from 1 atmospheric pressure to 20 atmospheric pressure; and
the post-exposure bake temperature is in a range from a boiling temperature of the protic solvent at 1 atmospheric pressure to a boiling temperature of the protic solvent at 20 atmospheric pressure.
7. The method of claim 5 , wherein applying a protic solvent over an EUV photoresist layer after exposure to EUV radiation comprises:
placing the substrate with the EUV photoresist layer thereupon in a container; and
dispensing the protic solvent into the container so that the EUV photoresist layer is immersed in the protic solvent.
8. The method of claim 7 , further comprising:
sealing the container to provide an enclosed volume with the protic solvent, the substrate, and the EUV photoresist layer therein; and
pressuring the enclosed volume to a post-exposure bake pressure greater than 1 atmospheric pressure.
9. The method of claim 8 , further comprising ramping a temperature of the substrate, the EUV photoresist layer, and the protic solvent to a boiling temperature of the protic solvent at the post-exposure bake pressure.
10. The method of claim 1 , wherein removing the protic solvent from the EUV photoresist layer is performed by spin-drying the EUV photoresist layer.
11. The method of claim 10 , wherein the spin-drying step is performed within a container in which the protic solvent is heated to the post-exposure bake temperature.
12. The method of claim 10 , wherein the spin-drying step is performed outside a container in which the protic solvent is heated to the post-exposure bake temperature on a separate drying station.
13. The method of claim 1 , wherein the post-exposure bake temperature comprises a boiling temperature of the protic solvent at a pressure to which the protic solvent is subjected while the EUV photoresist layer is immersed in the protic solvent or while the protic solvent is present over the EUV photoresist layer as the puddle.
14. The method of claim 1 , wherein applying the protic solvent comprises forming the puddle of the protic solvent by spraying or pouring the protic solvent over the EUV photoresist layer.
15. The method of claim 14 , wherein the protic solvent on the EUV photoresist layer is heated to the post-exposure bake temperature while the protic solvent is present over the EUV photoresist layer as the puddle, and wherein a lateral extent of the puddle of the protic solvent is limited to an area of the EUV photoresist layer.
16. The method of claim 1 , wherein applying the protic solvent comprises immersing the EUV photoresist layer in the protic solvent that fills a container or a tank, such that the protic solvent is laterally confined by a wall of the container or the tank, and the protic solvent on the EUV photoresist layer is heated to the post-exposure bake temperature while the EUV photoresist layer is immersed in the protic solvent.
17. The method of claim 1 , further comprising cooling the substrate after removing the protic solvent and prior to developing the EUV photoresist layer.