Multilayer mirror
There is provided a multilayer mirror ( 80 ) comprising a layer of a first material ( 84 ) and a layer of silicon ( 82 ). The layer of the first material and the layer of silicon form a stack of layers. An exposed region of the layer of silicon comprises a modification that is arranged to improve the robustness of the exposed region of silicon.
1. A multilayer mirror comprising:
a layer of a first material;
a layer of silicon;
the layer of the first material and the layer of silicon forming a stack of layers;
wherein only an exposed region of the layer of silicon comprises a modification that is arranged to improve robustness of the exposed region of the layer of the silicon.
2. The multilayer mirror of claim 1 , wherein the modification is arranged to improve the robustness of the exposed region of the layer of the silicon by at least one of:
reducing a reactivity of the exposed region of the layer of silicon with hydrogen or atomic hydrogen; and
improving a sputtering resistance of the exposed region of the layer of silicon.
3. The multilayer mirror of claim 2 , wherein the reactivity of the exposed region of the layer of silicon with hydrogen or atomic hydrogen is reduced by at least one of:
one or more implanted materials provided on a surface of the exposed region of the layer of silicon, or within the exposed region of the layer of silicon; and
a passivation layer covering, or forming part of, the exposed region of the layer of silicon.
4. The multilayer mirror of claim 2 , wherein the sputtering resistance of the exposed region of the layer of silicon is improved by at least one of:
one or more implanted materials provided on a surface of the exposed region of the layer of silicon, or within the exposed region of the layer of silicon; and
a passivation layer covering, or forming part of, the exposed region of the layer of silicon.
5. The multilayer mirror of claim 1 , wherein the modification comprises at least one of:
one or more implanted materials comprising at least one of boron, nitrogen and nitride, provided on a surface of the exposed region of the layer of silicon, or within the exposed region of the layer of silicon; and
a passivation layer covering, or forming part of the exposed region of the layer of silicon.
6. The multilayer mirror of claim 5 , wherein the passivation layer comprises one or more of a nitride layer, a silicon nitride layer, a boron glass layer, or a silicon oxynitride layer.
7. The multilayer mirror of claim 1 , wherein the exposed region of the layer of silicon is a peripheral region of the layer of silicon or a sidewall of the layer of silicon.
8. The multilayer mirror of claim 1 , wherein:
the multilayer mirror comprises at least one of a plurality of layers of the first material and a plurality of layers of silicon, such that:
the plurality of layers of silicon are separated by a layer of the first material, or
the plurality of layers of the first material are separated by a layer of silicon.
9. The multilayer mirror of claim 1 , wherein a plurality of exposed regions of the layer or layers of silicon comprises the modification.
10. The multilayer mirror of claim 1 , wherein a majority or substantially all of the exposed region or regions of the layer or layers of silicon comprise the modification.
11. A lithographic apparatus comprising:
an illumination system configured to generated a beam of radiation;
a patterning device configured to modulate the beam;
a projection system configured to direct the modulated beam onto a target portion of a substrate; and
multilayer mirror within one of the illumination or projection system, the multilayer mirror comprising:
a layer of a first material;
a layer of silicon;
the layer of the first material and the layer of silicon forming a stack of layers;
wherein only an exposed region of the layer of silicon comprises a modification that is arranged to improve robustness of the exposed region of the layer of the silicon.
12. A method comprising:
forming a stack of layers including a layer of a first material and a layer of silicon; and
modifying only an exposed region of the layer of silicon to improve robustness of the exposed region of silicon.
13. The method of claim 12 , wherein the modifying comprises:
reducing a reactivity of the exposed region of the layer of silicon with hydrogen or atomic hydrogen; or improving a sputtering resistance of the exposed region of the layer of silicon.
14. The method of claim 13 , wherein the reactivity of the exposed region of the layer of silicon with hydrogen or atomic hydrogen is reduced by at least one of:
implanting one or more material on a surface of the exposed region of the layer of silicon, or within the exposed region of the layer of silicon; and
providing a passivation layer that covers, or forms part of, the exposed region of the layer of silicon.
15. The multilayer mirror of claim 13 , wherein the sputtering resistance of the exposed region of the layer of silicon is improved by at least one of:
implanting one or more material on a surface of the exposed region of the layer of silicon, or within the exposed region of the layer of silicon; and
providing a passivation layer that covers, or forms part of, the exposed region of the layer of silicon.
16. The method of claim 12 , wherein modifying comprises at least one of:
implanting one or more material on a surface of the exposed region of the layer of silicon, or within the exposed region of the layer of silicon; and
providing a passivation layer that covers, or forms part of, the exposed region of the layer of silicon.