Photosensitive composition
View Patent ↗Photoresist compositions and methods suitable for depositing a thick photoresist layer in a single coating application are provided. Such photoresist layers are particularly suitable for use in chip scale packaging, for example, in the formation of metal bumps.
1. A method of forming a patterned layer on a substrate, comprising:
(a) disposing over a substrate a photosensitive layer comprising a composition comprising: a binder polymer prepared by free radical polymerization of acrylic acid and/or methacrylic acid with one or more monomers chosen from acrylate monomers, methacrylate monomers and vinyl aromatic monomers; a free radical polymerizable monomer bearing two or more ethylenically unsaturated groups, a free radical photoinitiator; and a stable free radical inhibitor, wherein the stable free radical inhibitor is present in the composition in an amount of from 0.04 to 0.3 wt % based on the total weight of the composition;
(b) imagewise exposing the photosensitive Layer to actinic radiation; and
(c) developing the exposed layer, thereby forming a patterned layer;
wherein (a) comprises coating the photosensitive layer by spin coating in a single application, and wherein one or more portion of the patterned layer has an aspect ratio of 1.5 or more.
2. The method of claim 1 , wherein (a) comprises coating the photosensitive layer to a dried thickness of at least 50 microns by spin coating in a single application.
3. The method of claim 1 , wherein the substrate is a semiconductor wafer, the method further comprising:
(d) depositing a metal over exposed areas of the substrate; and
(e) removing the patterned layer to provide a semiconductor wafer having metal bumps.
4. The method of claim 1 , wherein the stable free radical inhibitor comprises 2,2,6,6-tetramethyl-1-piperidinyloxy, 2,2-diphenyl-1-picrylhydrazyl, or a derivative thereof.
5. The method of claim 1 , wherein (a) comprises coating the photosensitive layer to a dried thickness of at least 100 microns by spin coating in a single application.
6. The method of claim 1 , wherein the binder polymer is prepared by free radical polymerization of ethyl acrylate, methyl methacrylate, and methacrylic acid.
7. A method of forming a patterned layer on a substrate, comprising:
(a) disposing over a substrate a photosensitive layer comprising a composition comprising: a binder polymer prepared by free radical polymerization of acrylic acid and/or methacrylic acid with one or more monomers chosen from acrylate monomers, methacrylate monomers and vinyl aromatic monomers; a free radical polymerizable monomer bearing two or more ethylenically unsaturated groups, a free radical photoinitiator; and a stable free radical inhibitor, wherein the stable free radical inhibitor is present in the composition in an amount of from 0.04 to 0.3 wt % based on the total weight of the composition;
(b) imagewise exposing the photosensitive layer to actinic radiation; and
(c) developing the exposed layer, thereby forming a patterned layer;
wherein the composition has a total solids content of 45 wt % or greater.
8. The method of claim 7 , wherein (a) comprises coating the photosensitive layer to a dried thickness of at least 50 microns by spin coating in a single application.
9. The method of claim 7 , wherein the substrate is a semiconductor wafer, the method further comprising:
(d) depositing a metal over exposed areas of the substrate; and
(e) removing the patterned layer to provide a semiconductor wafer having metal bumps.
10. The method of claim 7 , wherein the stable free radical inhibitor comprises 2,2,6,6-tetramethyl-1-piperidinyloxy, 2,2-diphenyl-1-picrylhydrazyl, or a derivative thereof.
11. The method of claim 7 , wherein (a) comprises coating the photosensitive layer to a dried thickness of at least 100 microns by spin coating in a single application.
12. The method of claim 7 , wherein the binder polymer is prepared by free radical polymerization of ethyl acrylate, methyl methacrylate, and methacrylic acid.
13. The method of claim 7 , wherein (a) comprises applying a dry-film photoresist to the substrate.