Patent Number: 
Section: claims

1. An extreme ultraviolet lithography process, comprising:providing an extreme ultraviolet (EUV) mask including an absorption region and a reflective region;illuminating the EUV mask by a radiation, wherein each light ray of the radiation incident on the EUV mask has an angle of incidence almost the same as a chief ray angle of incidence at the object side (CRAO), wherein the CRAO is less than three degrees;reflecting the radiation from the EUV mask providing a 0th order diffraction ray, a negative first diffraction order ray and a positive first diffraction order ray;collecting and directing the negative first diffraction order ray and the positive first diffraction order ray to expose a target; andreflecting the 0th order ray to an illuminator for reuse in another exposure. 2. The process of claim 1, wherein the CRAO is about zero degrees. 3. The process of claim 1, further comprising: providing the radiation wherein the radiation has a wavelength of between about 1 nanometer (nm) and about 100 nm. 4. The process of claim 1, further comprising: wherein the absorption region and the reflective region define a pattern for radiation incident the EUV mask. 5. The process of claim 1, wherein the negative first diffraction order ray has a distance from a pupil center in a pupil plane that is the same as a distance between the positive first diffraction order and the pupil center. 6. The process of claim 1, wherein the collecting the negative first diffraction order ray and the positive first diffraction order ray is performed by a projection optics box (POB). 7. An extreme ultraviolet lithography process, comprising:illuminating an EUV mask by a radiation wherein rays of the radiation incident on the EUV mask have an angle of incidence almost the same as the chief ray angle of incidence at the object side CRAO, wherein the CRAO is less than approximately 3 degrees;reflecting radiation from the EUV mask thereby generating diffracted light and 0th order diffraction light;using the diffracted light to expose a semiconductor wafer; anddirecting the 0th order diffraction light to the illuminator using a first projection optics box (POB). 8. The process of claim 7, further comprising:collecting the diffracted light including collecting light of −1st and +1st diffraction orders. 9. The process of claim 8, wherein the collecting the diffracted light includes collecting the diffracted light using a second POB different than the first POB. 10. The process of claim 7, wherein the EUV mask comprises:a low thermal expansion material (LTEM), wherein a reflective multi-layer (ML) is disposed above one surface of the LTEM substrate, wherein a patterned absorption layer is disposed above the ML; anda conductive layer above an opposite surface of the LTEM substrate. 11. The process of claim 10, wherein the ML includes a plurality of molybdenum-silicon (Mo—Si) film pairs, wherein the process further includes determining a thickness of each layer of the plurality of Mo—Si film pairs based on the CRAO. 12. The process of claim 7, wherein the using the diffracted light to expose the semiconductor wafer includes providing the semiconductor wafer with a photoresist sensitive to EUV radiation. 13. The process of claim 7, further comprising: using the 0th order diffraction light reflected back to the illuminator in a subsequent exposure. 14. An extreme ultraviolet lithography process, comprising:determining a chief ray angle of incidence at the object side (CRAO) of less than three degrees;receiving an extreme ultraviolet (EUV) mask, wherein the EUV mask comprises:a reflective multilayer (ML), wherein a first thickness of the ML is adjusted based on the CRAO; anda patterned absorption layer disposed above the ML and exposing reflective regions of the ML, wherein a second thickness of the patterned absorption layer is determined based on the CRAO;providing an extreme ultraviolet (EUV) radiation source;directing a radiation from the EUV radiation source to the EUV mask by an illuminator;illuminating the EUV mask by the radiation, wherein rays of the radiation incident on the EUV mask have an angle of incidence almost the same as the CRAO;reflecting light of a −1st diffraction order, a +1st diffraction order, and a 0th diffraction from the EUV mask;reflecting the 0th order diffraction order light to the illuminator; andreusing the reflected 0th order diffraction order light. 15. The process of claim 14, wherein the CRAO is about zero degrees. 16. The process of claim 14, wherein the reusing the reflected 0th order diffraction order light is performed by the illuminator. 17. The process of claim 14, wherein the reflecting the 0th order diffraction order light is performed by a first projection optics box (POB). 18. The process of claim 17, further comprising:collecting and directing the −1st diffraction order and the +1st diffraction order by a second POB to expose a target. 19. The process of claim 18, wherein the second POB includes a magnification of less than one. 20. The process of claim 14, further comprising:using the produced diffracted light of the −1st diffraction order and the +1st diffraction order to expose a target substrate.