Patent Number: 
Section: claims

1. An extreme ultraviolet lithography process, comprising:receiving an extreme ultraviolet (EUV) mask including an absorption region and a reflective region;providing a radiation;providing an illuminator;illuminating the EUV mask by the radiation, the radiation being directed to the EUV mask by the illuminator and a first projection optics box (POB),wherein rays of the radiation incident on the EUV mask have an angle of incidence almost the same as a chief ray angle of incidence at the object side (CRAO) of less than three degrees;producing diffracted light and non-diffracted light, wherein the producing the diffracted light and the non-diffracted light further includes:reflecting the radiation by the reflective region of the EUV mask; anddiffracting the reflected radiation by the absorptive region of the EUV mask;removing at least partially the non-diffracted light by reflecting the non-diffracted light using the first POBwherein the first POB includes at least one of EUV refractive optics and EUV reflective optics; andcollecting and directing the diffracted light by a second POB to expose a target. 2. The process of claim 1, wherein the EUV mask comprises:a low thermal expansion material (LTEM) substrate;a reflective multilayer (ML) above one surface of the LTEM substrate;a conductive layer above an opposite surface of the LTEM substrate; anda patterned absorption layer above the ML. 3. The process of claim 1, wherein the CRAO directed by the illuminator is about zero degree. 4. The process of claim 1, wherein a first portion of more than 70% of the non-diffracted light is removed by the first POB,wherein a second portion of the non-diffracted light is collected and directed by the second POB to expose the target. 5. The process of claim 1, wherein collecting the diffracted light includes collecting light of −1st and +1st diffraction orders, andwherein the light of −1st diffraction order has a distance from a pupil center in a pupil plane that is the same as a distance between the light of the +1st diffraction order and the pupil center. 6. The process of claim 1, wherein directing the diffracted light includes directing light of −1st and +1st diffraction orders towards the target, andwherein the second POB includes a magnification of less than one. 7. 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;illuminating the EUV mask by a radiation from an illuminator, wherein rays of the radiation incident on the EUV mask have an angle of incidence almost the same as the CRAO;producing diffracted light and non-diffracted light, wherein the producing the diffracted light and the non-diffracted light includes:producing shadows in a first portion of the reflective regions of the ML by the patterned absorption layer;reflecting the radiation by a second portion of the reflective regions of the ML; anddiffracting the reflected radiation by the patterned absorption layer;directing the non-diffracted light to the illuminator using a first projection optics box (POB); andcollecting and directing the diffracted light by a second POB to expose a semiconductor wafer. 8. The process of claim 7, wherein collecting the diffracted light includes collecting light of −1st and +1st diffraction orders. 9. The process of claim 7, wherein directing the diffracted light includes directing light of −1st and +1st diffraction orders towards the target. 10. The process of claim 7, wherein the EUV mask comprises:a low thermal expansion material (LTEM),wherein the ML is disposed above one surface of the LTEM substrate,wherein the 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 each of the plurality of Mo—Si film pairs has a thickness of about 7 nm, andwherein the ML has a reflectivity of about 70%. 12. The process of claim 10, wherein the ML includes a plurality of molybdenum-beryllium (Mo—Be) film pairs, andwherein a thickness of each of the plurality of Mo—Be film pairs depends on the CRAO. 13. The process of claim 10, wherein the patterned absorption layer includes a plurality of layers, andwherein each of the plurality of the layers includes at least one material selected from a group consisting of chromium, chromium oxide, chromium nitride, titanium, titanium oxide, titanium nitride, tantalum, tantalum oxide, tantalum nitride, tantalum oxynitride, tantalum boron oxide, tantalum boron nitride, tantalum boron oxynitride, aluminum, aluminum oxide, silver, silver oxide, palladium, copper, ruthenium, and molybdenum. 14. The process of claim 10, the EUV mask further comprising:a capping layer above the ML; anda buffer layer above the capping layer and below the absorption layer. 15. The process of claim 14, wherein the capping layer includes silicon, andwherein the LTEM includes TiO2 doped SiO2. 16. The process of claim 14, wherein the buffer layer includes at least one material selected from a group consisting of Ru, RuB, RuSi, Cr, Cr oxide, and Cr nitride. 17. The process of claim 14, wherein the capping layer and the buffer layer are a single layer. 18. 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;producing diffracted light and non-diffracted light, wherein the producing the diffracted light and the non-diffracted light includes:producing shadows in a first portion of the reflective regions of the ML by the patterned absorption layer;reflecting the radiation by a second portion of the reflective regions of the ML; anddiffracting the reflected radiation by the patterned absorption layer;reflecting the non-diffracted light to the illuminator by a projection optics box (POB); andreusing the non-diffracted light reflected by the POB. 19. The process of claim 18, wherein the CRAO is about zero degree. 20. The process of claim 18, further comprising:collecting and directing the diffracted light by another POB to expose a target.