Claims
- 1. A reflective mask useful for transferring a pattern to a semiconductor substrate comprising:
a mask substrate; a reflective stack formed over the mask substrate, wherein an uppermost surface of the reflective stack defines a top plane of the mask; and an opening formed partially through the reflective stack from the top plane, wherein the opening location corresponds to a region where lower reflectivity than that provided by the reflective stack is desired.
- 2. The reflective mask of claim 1 wherein the reflective stack comprises a stack of alternating first and second layers, wherein a material of the first layer is a transmissive material and a material of the second layer has an index of refraction substantially different than an index of refraction of the material of the first layer.
- 3. The reflective mask of claim 2 wherein the stack of alternating layers comprises alternating layers of molybdenum and silicon.
- 4. The reflective mask of claim 1 further comprising an embedded etch stop layer embedded within the reflective stack, and wherein a bottom of the opening is defined by the embedded etch stop layer.
- 5. The reflective mask of claim 4 further comprising an absorber layer formed over the embedded etch stop layer within the opening.
- 6. The reflective mask of claim 5 wherein the embedded etch stop layer and absorber layer each comprise chromium.
- 7. A reflective mask useful for transferring a pattern to a semiconductor substrate comprising:
a mask substrate; a lower multilayer reflective stack formed over the mask substrate; an etch stop layer formed on the lower multilayer reflective stack; an upper multilayer reflective stack formed over the etch stop layer; and an opening formed through the upper multilayer reflective stack and exposing the etch stop layer.
- 8. The reflective mask of claim 7 wherein the etch stop layer has a thickness of approximately λ cos θ/(2n), wherein λ is a wavelength of EUV radiation to be used; n is an index of refraction of the etch stop layer; and θ is an angle of incidence of EUV radiation on the reflective mask to be used.
- 9. The reflective mask of claim 7 further comprising an absorber layer formed over the etch stop layer within the opening.
- 10. The reflective mask of claim 9 wherein:
the opening corresponds to a dark region; areas of the upper multilayer reflective stack adjacent the opening correspond to bright regions; the upper multilayer reflective stack defines a top plane of the reflective mask; and the thickness of the absorber layer is chosen so that reflection of EUV radiation at the top plane within the opening is 3-20 percent of reflection of EUV radiation at the top plane within the upper multilayer reflective stack.
- 11. The reflective mask of claim 10 wherein the lower and upper multilayer reflective stacks each comprise periods of alternating layers of different materials, and wherein a number of periods for each of the lower and upper multilayer reflective stack is determined, at least in part, by a requirement that EUV radiation reflected in the dark region is approximately 180° out of phase with respect to EUV radiation reflected in the bright region.
- 12. The reflective mask of claim 9 wherein the absorber layer comprises chromium.
- 13. The reflective mask of claim 9 wherein the absorber layer has a thickness of between approximately 10 to 50 nanometers.
- 14. The reflective mask of claim 7 wherein the etch stop layer comprises a material selected from a group consisting of chromium, ruthenium, chrome oxide, chrome nitride, boron carbide, zirconium, tantalum oxide, tantalum nitride, tantalum silicon nitride.
- 15. The reflective mask of claim 7 wherein the etch stop layer comprises chromium.
- 16. The reflective mask of claim 7 wherein the etch stop layer has a thickness of between approximately 5 to 20 nanometers.
- 17. The reflective mask of claim 7 wherein the lower and upper multilayer reflective stacks each comprise periods of alternating layers of different materials, and wherein a number of periods in the lower multilayer reflective stack is between 10 and 20.
- 18. The reflective mask of claim 17 wherein a number of periods in the upper multilayer reflective stack is between 20 and 30.
- 19. A method for making a reflective mask useful for transferring a pattern to a semiconductor substrate comprising:
providing a mask substrate; forming a reflective portion over the mask substrate; etching an opening through the reflective portion; and forming an absorber portion within the opening.
- 20. The method of claim 19 wherein forming the reflective portion comprises forming a series of alternating first and second layers, wherein the first layer comprises a transmissive material and the second layer has an index of refraction substantially different than an index of refraction of the first layer.
- 21. The method of claim 20 wherein the series of alternating layers comprises alternating layers of molybdenum and silicon.
- 22. The method of claim 19 wherein the absorber portion comprises chromium.
- 23. The method of claim 19 wherein:
the opening corresponds to a dark region; areas of the upper multilayer reflective stack adjacent the opening correspond to bright regions; the upper multilayer reflective stack defines a top plane of the reflective mask; and the thickness of the absorber layer is chosen so that reflection of EUV radiation at the top plane within the opening is 3-20 percent of reflection of EUV radiation at the top plane within the upper multilayer reflective stack.
- 24. A method for making a reflective mask useful for transferring a pattern to a semiconductor substrate using extreme ultraviolet (EUV) radiation comprising:
providing a mask substrate; forming a lower multilayer reflective stack over the mask substrate; forming an etch stop layer over the lower multilayer reflective stack; forming an upper multilayer reflective stack on the etch stop layer; and etching an opening through the upper multilayer reflective stack to expose the etch stop layer.
- 25. The method of claim 24 wherein forming a lower and an upper multilayer reflective stack each comprise forming a series of alternating first and second layers, wherein the first layer comprises a transmissive material and the second layer has an index of refraction substantially different than an index of refraction of the first layer.
- 26. The method of claim 25 wherein the series of alternating layers in each of the lower and upper multilayer reflective stacks comprises alternating layers of molybdenum and silicon.
- 27. The method of claim 25 wherein a combination of one first layer and one second layer constitutes a period, and a number of periods in the lower multilayer reflective stack is between 10 and 20.
- 28. The method of 25 wherein the etch stop layer is formed to have a thickness of approximately λ cos θ/(2n), wherein λ is a wavelength of EUV radiation to be used; n is an index of refraction of the etch stop layer; and θ is an angle of incidence of EUV radiation on the reflective mask.
- 29. The method of claim 24 further comprising forming an absorber layer formed over the etch stop layer within the opening.
- 30. The method of claim 29 wherein the absorber layer is formed to have a thickness of between approximately 10 to 50 nanometers.
- 31. The method of claim 24 wherein the etch stop layer comprises a material selected from a group consisting of chromium, ruthenium, chrome oxide, chrome nitride, boron carbide, zirconium, tantalum oxide, tantalum nitride, tantalum silicon nitride.
- 32. The method of claim 31 wherein the etch stop layer comprises chromium.
- 33. The method of claim 31 wherein the etch stop layer has a thickness of between approximately 5 to 20 nanometers.
- 34. The method of claim 24 further comprising the step of forming a hardmask on the upper multilayer reflective stack, and wherein the step of etching an opening comprises etching an opening using the hardmask as an etch mask.
- 35. The method of claim 34 wherein the hardmask comprises chromium.
- 36. A method for patterning a photoresist layer on a semiconductor substrate using a reflective mask comprising providing a semiconductor substrate;
forming a photoresist layer over the semiconductor substrate; providing a reflective mask, the reflective mask comprising:
a mask substrate; a lower multilayer reflective stack formed over the mask substrate; an etch stop layer formed on the lower multilayer reflective stack; an upper multilayer reflective stack formed over the etch stop layer; and an opening formed through the upper multilayer reflective stack and exposing the etch stop layer. projecting incident radiation on the reflective mask; reflecting the incident radiation from the reflective mask as reflected radiation; and illuminating the photoresist layer with the reflected radiation.
RELATED APPLICATIONS
[0001] This application is related to U.S. patent application Ser. No. 09/940,241 filed Aug. 27, 2001, entitled “Method of Forming a Pattern on a Semiconductor Wafer Using an Attenuated Phase Shifting Reflective Mask” and assigned to the current assignee hereof. This application is related to U.S. patent application Ser. No. 09/939,184 filed Aug. 24, 2001, entitled “Method of Making an Integrated Circuit Using a Reflective Mask” and assigned to the current assignee hereof and incorporated herein by reference. This application is related to U.S. patent application Ser. No. 09/414,735 filed Oct. 8, 1999, entitled “Method of Manufacturing a Semiconductor Component” and assigned to the current assignee hereof and incorporated herein by reference.