Passivation of multi-layer mirror for extreme ultraviolet lithography
A reflector structure suitable for extreme ultraviolet lithography (EUVL) is provided. The structure comprises a substrate having a multi-layer reflector. A capping layer is formed over the multi-layer reflector to prevent oxidation. In an embodiment, the capping layer is formed of an inert oxide, such as Al 2 O 3 , HfO 2 , ZrO 2 , Ta 2 O 5 , Y 2 O 3 -stabilized ZrO 2 , or the like. The capping layer may be formed by reactive sputtering in an oxygen environment, by non-reactive sputtering wherein the materials are sputtered directly from the respective oxide targets, by non-reactive sputtering of the metallic layer followed by full or partial oxidation (e.g., by natural oxidation, by oxidation in oxygen-containing plasmas, by oxidation in ozone (O 3 ), or the like), by atomic level deposition (e.g., ALCVD), or the like.
1 . A reflective device suitable for use in extreme ultraviolet or soft x-ray applications, the reflective device comprising:
a substrate;
a multi-layer reflector formed on the substrate; and
a capping layer formed on the multi-layer reflector, the capping layer comprising an oxide that is chemically inert in an oxidizing environment.
2 . The reflective device of claim 1 , wherein the substrate comprises a low-thermal expansion material (LTEM).
3 . The reflective device of claim 2 , wherein the substrate comprises ultra-low expansion (ULE) glass.
4 . The reflective device of claim 2 , wherein the substrate comprises Zerodur®.
5 . The reflective device of claim 1 , wherein the multi-layer reflector comprises alternating layers of a high atomic number Z material and a low atomic number Z material.
6 . The reflective device of claim 5 , wherein the high atomic number Z material comprises molybdenum.
7 . The reflective device of claim 5 , wherein the low atomic number Z material comprises silicon.
8 . The reflective device of claim 5 , wherein each pair of the high atomic number Z material and the low atomic number Z material is about 6.8 nm in thickness.
9 . The reflective device of claim 1 , wherein the capping layer comprises Al 2 O 3 , HfO 2 , ZrO 2 , Ta 2 O 5 , Y 2 O 3 -stabilized ZrO 2 , or a combination thereof.
10 . The reflective device of claim 1 , wherein the capping layer comprises a plurality of layers.
11 . The reflective device of claim 1 , wherein the capping layer is about 1 nm to about 5 nm in thickness.
12 . A method of forming a reflective device suitable for use in extreme ultraviolet or soft x-ray applications, the method comprising:
providing a substrate having a multi-layer reflector formed thereon; and
forming a capping layer over the multi-layer reflector, the capping layer comprising an oxide that is chemically inert in an oxidizing environment.
13 . The method of claim 12 , wherein the substrate comprises a low-thermal expansion material (LTEM).
14 . The method of claim 13 , wherein the substrate comprises ultra-low expansion (ULE) glass.
15 . The method of claim 13 , wherein the substrate comprises Zerodur®.
16 . The method of claim 12 , wherein the multi-layer reflector comprises alternating layers of a high atomic number Z material and a low atomic number Z material.
17 . The method of claim 16 , wherein the high atomic number Z material comprises molybdenum.
18 . The method of claim 16 , wherein the low atomic number Z material comprises silicon.
19 . The method of claim 16 , wherein each pair of the high atomic number Z material and the low atomic number Z material is about 6.8 nm in thickness.
20 . The method of claim 16 , wherein the capping layer comprises Al 2 O 3 , HfO 2 , ZrO 2 , Ta 2 O 5 , Y 2 O 3 -stabilized ZrO 2 , or a combination thereof.
21 . The method of claim 12 , wherein the capping layer comprises a plurality of layers.
22 . The method of claim 12 , wherein the capping layer is about 1 nm to about 5 nm in thickness.
23 . The method of claim 12 , wherein the forming comprises performing a reactive sputter process in an oxygen atmosphere using metallic sputter targets.
24 . The method of claim 12 , wherein the forming comprises performing a non-reactive sputter process wherein the inert oxide is sputtered directly from a respective oxide target.
25 . The method of claim 12 , wherein the forming comprises performing a non-reactive sputter process of a metallic layer and fully or partially oxidizing the metallic layer.
26 . The method of claim 12 , wherein the forming comprises performing an atomic layer deposition process.
27 . A method of patterning a semiconductor device, the method comprising:
providing a semiconductor wafer;
applying a photoresist material; and
exposing a portion of the photoresist material, the exposing using a reflective device suitable for use in extreme ultraviolet or soft x-ray applications, the reflective device having a capping layer over a multi-layer reflector, the capping layer comprising an oxide that is chemically inert in an oxidizing environment.
28 . The method of claim 27 , wherein the reflective device further comprises a substrate formed of a low-thermal expansion material (LTEM).
29 . The method of claim 28 , wherein the substrate comprises ultra-low expansion (ULE) glass.
30 . The method of claim 28 , wherein the substrate comprises Zerodur®.
31 . The method of claim 27 , wherein the multi-layer reflector comprises alternating layers of a high atomic number Z material and a low atomic number Z material.
32 . The method of claim 31 , wherein the high atomic number Z material comprises molybdenum.
33 . The method of claim 31 , wherein the low atomic number material comprises silicon.
34 . The method of claim 31 , wherein each pair of the high atomic number Z material and the low atomic number Z material is about 6.8 nm in thickness.
35 . The method of claim 27 , wherein the capping layer comprises Al 2 O 3 , HfO 2 , ZrO 2 , Ta 2 O 5 , Y 2 O 3 -stabilized ZrO 2 , or a combination thereof.
36 . The method of claim 27 , wherein the capping layer comprises a plurality of layers.
37 . The method of claim 27 , wherein the capping layer is about 1 nm to about 5 nm in thickness.