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US 9,804,309 B1Granted
Reducing extrinsic stress in thin film optical mirrors and filters for deep ultraviolet
AssigneeKLA-Tencor Corporation
InventorJohn Lehan
Life of this patent
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Abstract
A multilayer coating has a substrate, an optical layer, and a buffer layer between the substrate and the optical layer. The buffer layer has a coefficient of thermal expansion between that of the substrate and the optical layer. The multilayer coating has properties that enable its use in deep ultraviolet (DUV) wavelengths, such as for a multilayer mirror or edge filter. This multilayer coating with a buffer layer provides improved thermal stability and lifetime.
Claims19
A multilayer coating comprising:
- a substrate having a first coefficient of thermal expansion, wherein a thickness of the substrate is at least 100 μm;
- at least one optical layer having a second coefficient of thermal expansion, wherein a thickness of the optical layer is at least 0.5 μm;
- and
- a buffer layer disposed between the substrate and the optical layer, wherein the buffer layer has a third coefficient of thermal expansion having a value between the first coefficient of thermal expansion and the second coefficient of thermal expansion, wherein a thickness of the buffer layer is from 2 μm to 4 μm, wherein the buffer layer comprises a gradient of a first material and a second material such that a percentage of the second material increases with thickness of the buffer layer from the substrate to the optical layer, and wherein a surface of the buffer layer disposed on the substrate has more of the first material than the second material and a surface of the buffer layer disposed on the optical layer has more of the second material than the first material.
1 more element
A method of manufacturing a multilayer coating comprising:
- providing a substrate having a first coefficient of thermal expansion, wherein a thickness of the substrate is at least 100 μm;
- applying a buffer layer on the substrate, wherein the buffer layer has a third coefficient of thermal expansion and a thickness of the buffer layer is from 2 μm to 4 μm;
- and
- applying an optical layer on the buffer layer, the optical layer having a second coefficient of thermal expansion and a thickness of the optical layer is at least 0.5 μm;
- wherein the third coefficient of thermal expansion has a value between the first coefficient of thermal expansion and the second coefficient of thermal expansion, wherein the buffer layer comprises a gradient of a first material and a second material such that a percentage of the second material increases with thickness of the buffer layer from the substrate to the optical layer, and wherein a surface of the buffer layer disposed on the substrate has more of the first material than the second material and a surface of the buffer layer disposed on the optical layer has more of the second material than the first material.
2 more elements
Dependencies are inferred from the claim text.