Method for structuring a lithography mask
View Patent ↗A method for structuring a lithograph mask by forming a cured, electrically-conductive layer on a mask structure having a radiation-transmissive substrate and a mask layer at least in portions of the surface of the radiation-transmissive substrate before applying a resist layer, so that during a subsequent irradiation of the resist layer by means of an electronic printing, the electrically conductive layer ensures a good charge elimination. By using a cured, electrically conductive layer, no intermixing effects between the electrically-conductive layer and the resist layer occur, and the electrically-conductive layer will be stable during subsequent development steps and not stripped off.
1. A method for structuring a lithographic mask comprising the sequential steps of:
preparing a mask substrate comprising a radiation-transmissive substrate having a mask layer in at least partial regions, said mask layer being selected from a group consisting of a radiation-impermeable layer, a half-tone layer and a combination of a half-tone layer and a radiation-impermeable layer;
applying at least one curable electrically-conductive layer over the mask layer and exposed portions of the radiation-transmissive substrate;
curing the curable, electrically-conductive layer so that it becomes essentially insoluble;
applying a resist layer on the cured, electrically-conductive layer;
electron printing the desired patterns on the resist layer;
developing the resist layer to remove partial regions of the resist layer;
removing the cured, electrically-conductive layer in those regions that are no longer covered by the resist layer; and
structuring exposed portions of the radiation-impermeable substrate and the mask layer which are no longer covered by the resist layer and the cured electrically-conductive layer.
2. A method according to claim 1 , wherein the radiation-transmissive substrate is composed of silica glass.
3. A method according to claim 2 , wherein the mask layer is a radiation-permeable layer comprised of a chrome layer.
4. A method according to claim 1 , wherein at least one of the steps of applying the curable, electrically-conductive layer and the resist layer is a step of spinning the layer onto the mask substrate.
5. A method according to claim 1 , wherein the step of curing the curable, electrically-conductive layer is by a thermal curing.
6. A method according to claim 1 , which includes, before curing the curable, electrically-conductive layer, applying a first drying step to remove solvent from the material.
7. A method according to claim 6 , which includes, prior to the step of irradiating, performing a second drying step to remove solvent from the resist layer.
8. A method according to claim 1 , which includes thermally fixing the exposed resist layer before the step of developing.
9. A method according to claim 1 , wherein the step of developing utilizes an aqueous, alkaline developer solution.
10. A method according to claim 1 , wherein the step of developing utilizes a solution of 2.38 weight % tetramethyl ammonium hydroxide in water.
11. A method according to claim 1 , wherein the step of removing portions of the cured, electrically-conductive layer utilizes a plasma etching.
12. A method according to claim 11 , wherein the step of removing exposed portions of the mask substrate utilizes a plasma etching.
13. A method according to claim 12 , wherein the plasma etching for removing the exposed portions of the mask substrate is an ion plasma etching.
14. A method according to claim 13 , wherein the plasma etching for removing the electrically-conductive layer is an oxygen ion plasma etching.
15. A method according to claim 1 , which includes, subsequent to structuring the mask substrate, removing the remaining resist layer and cured, electrically-conductive layer.