Radiation source, lithographic apparatus, and device manufacturing method

1. A spectral purity filter configured to transmit extreme ultraviolet (EUV) radiation and to deflect non-EUV secondary electromagnetic radiation, the spectral purity filter comprising a body of material having a transmissivity for EUV radiation in the range of 5-20 nm of at least 20% and a layer of material having reflection to the non-EUV secondary electromagnetic radiation of at least 50%, said layer being located on a radiation incident side of the body.

2. The spectral purity filter according to claim 1 , further comprising a layer of high emissivity material at a radiation exit surface of the body.

3. The spectral purity filter according to claim 2 , wherein the emissivity of the material is greater than 0.3.

4. The spectral purity filter according to claim 2 , wherein the layer of high emissivity material is located on a radiation incident side of the said layer of material.

5. The spectral purity filter according to claim 1 , wherein the layer of material having reflection to the non-EUV secondary electromagnetic radiation is selected from the group: molybdenum, ruthenium, gold, copper and carbon.

6. The spectral purity filter according to claim 1 , wherein the layer of material has at least 10% absorption for electromagnetic radiation having a wavelength in a sub-micrometer range.

7. A spectral purity filter configured to transmit at least 20% of extreme ultraviolet (EUV) radiation in the range of 5-20 nm and to deflect at least 50% of non-EUV secondary electromagnetic radiation, the spectral purity filter comprising a body of material and a layer of high emissivity material having emissivity of at least 0.3, said layer of high emissivity material being arranged on a radiation exit surface of the body.

8. The spectral purity filter according to claim 7 , wherein the layer of high emissivity material is located on a radiation incident side of the body.

9. The spectral purity filter according to claim 7 , wherein the body comprises a multilayer structure of material transmissive of EUV radiation and material suppressive of non-EUV secondary electromagnetic radiation.

10. The spectral purity filter according to claim 7 , wherein a material of the body is selected from the group: rubidium (Rb), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), carbon (C), ruthenium (Ru), and silicon (Si).

11. A source module constructed to generate extreme ultraviolet (EUV) radiation and to output the EUV radiation and non-EUV secondary electromagnetic radiation, the source module comprising a spectral purity filter configured to transmit extreme ultraviolet (EUV) radiation and to deflect non-EUV secondary electromagnetic radiation, the spectral purity filter comprising a body of material having a transmissivity for EUV radiation in the range of 5-20 nm of at least 20% and a layer of material having reflection to the non-EUV secondary electromagnetic radiation of at least 50%, said layer being located on a radiation incident side of the body.

12. A lithographic apparatus arranged to project a pattern from a patterning device onto a substrate, the lithographic apparatus comprising a spectral purity filter configured to transmit extreme ultraviolet (EUV) radiation and to deflect non-EUV secondary electromagnetic radiation, the spectral purity filter comprising a body of material having a transmissivity for EUV radiation in the range of 5-20 nm of at least 20% and a layer of material having reflection to the non-EUV secondary electromagnetic radiation of at least 50%, said layer being located on a radiation incident side of the body.

13. A device manufacturing method comprising:

generating radiation comprising extreme ultraviolet (EUV) radiation and non-EUV secondary electromagnetic radiation using a radiation source;

filtering the radiation to transmit EUV radiation and deflect non-EUV secondary electromagnetic radiation using a spectral purity filter comprising a body of material having at least 50% transmissivity to EUV radiation in the range of 5-20 nm and a layer of material having at least 50% reflection of non-EUV secondary electromagnetic radiation located on a radiation incident side of the body; and

projecting a patterned beam of the transmitted EUV radiation onto a substrate.

14. A device manufacturing method comprising:

generating radiation comprising extreme ultraviolet (EUV) radiation and non-EUV secondary electromagnetic radiation using a radiation source;

filtering the radiation to transmit EUV radiation and deflect non-EUV secondary electromagnetic radiation using a spectral purity filter comprising a body of material having at least 20% transmissivity to EUV radiation in the range of 5-20 nm and a layer material having emissivity of at least 0.3 at a radiation exit surface of the body; and

projecting a patterned beam of the transmitted EUV radiation onto a substrate.

15. The spectral purity filter according to claim 6 , wherein the layer of material has at least 50% absorption for electromagnetic radiation having a wavelength in a sub-micrometer range.

16. The spectral purity filter according to claim 1 , wherein the body of material is constructed to absorb at least 90% of the non-EUV secondary electromagnetic radiation that enters the body.

17. The spectral purity filter according to claim 1 , wherein the body of material comprises layers of Zr and Si.

18. The spectral purity filter according to claim 17 , wherein the body of material comprises a layer structure of Zr/ZrSi 2 /Si/ZrSi 2 /Zr.

19. The spectral purity filter according to claim 18 , wherein a thickness of each layer of the layer structure is in the range of 0.2 nm- 10 nm.