EUV active films for EUV lithography
A method of processing a substrate that includes forming over the substrate an extreme ultraviolet (EUV)-active photoresist film including a network of metal oxide terminated with alkoxy groups and patterning the EUV-active photoresist film with EUV lithography.
1. A method of processing a substrate, the method comprising:
forming a metal alkoxide by exposing a metal precursor to an alcohol, the metal alkoxide being an intermediate for forming a network of metal oxide, the metal precursor comprising an extreme ultraviolet (EUV) metal and ligands, each of the ligands comprising an alkoxy group, an amine, a carboxylate, or a halogen, the metal precursor not comprising a metal-carbon bond;
forming over the substrate an EUV-active photoresist film comprising the network of metal oxide; and
patterning the EUV-active photoresist film with EUV lithography.
2. The method of claim 1 , wherein the metal oxide comprises an alkoxy group comprising a hydrogen at a β position relative to oxygen.
3. The method of claim 1 , wherein the metal oxide is a tin oxide.
4. The method of claim 1 , wherein the metal oxide comprises an ethoxide, an iso-propoxide, a tert-butoxide, a cyclohexyl alkoxide, a cyclohexene alkoxide, or a cyclohexadiene alkoxide.
5. The method of claim 1 , wherein forming the metal alkoxide comprises:
before exposing the metal precursor to the alcohol, exposing the substrate to a vapor comprising the metal precursor; and
wherein forming the EUV-active photoresist film comprises
exposing the metal alkoxide to an oxidant to form metal-oxygen-metal bonds by replacing one or more of the ligands of the metal alkoxide.
6. The method of claim 1 , wherein forming the EUV-active photoresist film comprises:
depositing a layer comprising metal alkoxide over the substrate by exposing the substrate to a vapor comprising the metal alkoxide; and
exposing the layer comprising metal alkoxide to an oxidant to form metal-oxygen-metal bonds by replacing one or more ligands of the metal alkoxide.
7. The method of claim 6 , wherein the oxidant comprises oxygen, ozone, water, air, or hydrogen peroxide.
8. The method of claim 6 , wherein the vapor and the oxidant are introduced simultaneously into a processing chamber holding the substrate.
9. The method of claim 1 , wherein the forming comprises:
depositing, in a plasma processing chamber, a layer comprising metal alkoxide over the substrate by exposing the substrate to a vapor comprising the metal alkoxide; and
oxidizing the layer comprising metal alkoxide by exposure to oxygen radicals generated within the plasma processing chamber to form the network of metal oxide.
10. The method of claim 1 , wherein patterning the EUV-active photoresist film comprises:
converting one or more of the alkoxy groups in the EUV-active photoresist film to hydroxy groups; and
converting the hydroxy groups to form additional metal-oxygen-metal bonds in the network of metal oxide.
11. A method of processing a substrate in a plasma processing chamber, the method comprising:
exposing the substrate in the plasma processing chamber to a first vapor comprising a metal precursor, the metal precursor comprising an extreme ultraviolet (EUV) metal and ligands, each of the ligands comprising an alkoxy group, an amine, a carboxylate, or a halogen, the metal precursor not comprising a metal-carbon bond;
exposing the substrate in the plasma processing chamber to a second vapor comprising an alcohol having a hydrogen in a β-position relative to oxygen;
forming a photoresist film comprising a metal alkoxide over the substrate by exposing the substrate in the plasma processing chamber to a third vapor comprising an oxidant; and
oxidizing the photoresist film by exposure to oxygen radicals generated within the plasma processing chamber to form a network of metal oxide.
12. The method of claim 11 , wherein the metal is tin, wherein the exposing of the substrate to the first vapor comprises chemically adsorbing the metal precursor onto the substrate, wherein the exposing of the substrate to the second vapor comprises reacting the alcohol with the adsorbed metal precursor to form a tin alkoxy group, and wherein the exposing of the substrate to the third vapor comprises oxidizing the adsorbed metal precursor to form a tin-oxide network comprising tin-oxygen-tin bonds.
13. The method of claim 11 , further comprising:
alternating the exposing of the substrate to the first vapor and the exposing of the substrate to the second vapor more than once; and
between the exposing of the substrate to the first vapor and the exposing of the substrate to the second vapor, performing a purge or degassing step to remove residual portions of the first vapor, the second vapor, or both.
14. The method of claim 11 , further comprising alternating the exposing of the substrate to the first vapor and the exposing of the substrate to the second vapor more than once, wherein the exposing of the substrate to the first vapor and the exposing of the substrate to the second vapor are overlapped in time.
15. A method of extreme ultraviolet (EUV) lithography, the method comprising:
forming a tin alkoxide by exposing a tin precursor to an alcohol, the tin alkoxide being an intermediate for forming a network of tin oxide, the tin precursor comprising tin and ligands, each of the ligands comprising an alkoxy group, an amine, a carboxylate, or a halogen, the tin precursor not comprising a tin-carbon bond;
forming an EUV-active photoresist layer over a substrate, the EUV-active photoresist layer comprising the network of tin oxide;
exposing the substrate to an EUV irradiation having passed through an optical mask that comprises patterns to form exposed regions of the EUV-active photoresist layer, one or more alkoxy groups in the exposed regions undergoing β-hydrogen elimination to form a tin hydroxide by eliminating an alkene; and
developing the EUV-active photoresist layer.
16. The method of claim 15 , further comprising, after exposing the substrate to the EUV irradiation, performing a post-exposure bake to form tin-oxygen-tin bonds by condensing hydroxy groups of the tin hydroxides.
17. The method of claim 15 , wherein developing the EUV-active photoresist layer removes unexposed regions of the EUV-active photoresist layer.
18. The method of claim 15 , wherein developing the EUV-active photoresist layer is performed by a wet process.
19. The method of claim 15 , wherein developing the EUV-active photoresist layer is performed by a dry process using a plasma process, a thermal process, or both.
20. The method of claim 15 , further comprising, before developing the EUV-active photoresist layer, performing an area selective deposition process to form a material layer selectively over the exposed regions of the EUV-active photoresist layer.