Method for manufacturing attenuated phase-shift masks and devices obtained therefrom
View Patent ↗One inventive aspect relates to an attenuated phase shift mask suitable for hyper NA lithographic processing of a device, to a method of making such a mask and to hyper NA lithographic processing using such a mask. The attenuated phase shift mask is made taking into the effect of the numerical aperture of the lithographic system on which the attenuated phase shift mask is to be used.
1. A method of designing an embedded attenuated phase shift mask or mask blank for use in a lithographic process, the mask or mask blank comprising a halftone stack, the mask or mask blank being suitable for off-axis illumination and/or hyper numerical aperture (NA), the method comprising:
selecting mask setting values for the phase shift mask or mask blank and process parameter values for the lithographic process, the process parameter values comprising at least a numerical aperture equal to or larger than about 1,
selecting an image performance parameter,
performing an aerial image simulation using the selected mask setting values and deriving from the aerial image simulation the corresponding value for the image performance parameter,
evaluating the derived image performance parameter value with respect to a predetermined image performance parameter criterion, and
if the derived image performance parameter does not fulfill the image performance parameter criterion, adjusting the mask setting values based on the derived image performance parameter and repeating the performing a simulation and the evaluating,
wherein adjusting the mask setting values based on the derived image performance parameter comprises adjusting a selected thickness of an absorber and/or phase shift material taking into account said derived performance parameter.
2. The method of claim 1 , wherein the image performance parameter is one of the following: the image contrast in the resist, a depth of focus, an exposure latitude, a polarization effects of the mask, a mask error enhancement factor, and a linewidth sensitivity to illuminator polarization.
3. The method of claim 1 , wherein selecting mask setting values for the phase shift mask or mask blank comprises selecting a type and number of the material(s) of the halftone stack.
4. The method of claim 3 , wherein selecting the type and number of material(s) of the halftone stack comprises selecting an absorber material and a phase-shift material.
5. The method of claim 4 , wherein the absorber material is a metal and the phase-shift material is a dielectric.
6. The method of claim 5 , wherein the absorber material is chromium or tantalum, and the phase-shift material is silicon oxide or silicon oxynitride.
7. The method of claim 4 wherein selecting mask setting values for the phase shift mask or mask blank further comprises selecting the thickness of the absorber material and/or of the phase-shift material for providing a maximum exposure latitude of at least about 12%.
8. An embedded attenuated phase-shift mask comprising a transparent substrate, and a halftone stack, the halftone stack comprising an absorber material and a phase-shift material, the thickness of the absorber material and the thickness of the phase-shift material being determined taking into account off-axis illumination and taking further into account a numerical aperture equal to or larger than about 1.
9. The phase-shift mask of claim 8 , wherein the halftone stack is configured as a bilayer stack comprising a layer of absorber material and a layer of phase-shift material.
10. The phase-shift mask of claim 8 , wherein the halftone stack is configured as a multilayered stack of an alternating sequence of absorber material and phase-shift material.
11. The phase-shift mask of claim 8 , wherein the absorber material is a metal, and the phase-shift material is a dielectric.
12. The phase-shift mask of claim 11 , wherein the absorber material is Tantalum having a thickness in the range of approximately 25 nm to 45 nm, preferably in the range 25 nm to 35 nm, more preferably about 30 nm, and the phase-shift material is silicon oxide having a thickness in the range of approximately 135 nm to 140 nm, preferably about 140 nm.
13. The phase-shift mask of claim 11 , wherein the absorber material is Chromium having a thickness in the range of approximately 45 nm to 70 nm, preferably in the range 45 nm to 60 nm, more preferably about 50 nm, and the phase-shift material is silicon oxynitride having a thickness in the range of approximately 90 nm to 110 nm, preferably about 100 nm.
14. A mask blank for manufacturing of an embedded attenuated phase shift mask according to claim 8 .
15. A method of lithographic processing of a device, wherein the method comprises using off-axis illumination and an embedded attenuated phase shift mask according to claim 8 .
16. The phase-shift mask of claim 8 , wherein the absorber material is chromium or tantalum, and the phase-shift material is silicon oxide or silicon oxynitride.
17. A computer-readable medium having a computer program product stored therein for executing the method according to claim 1 .
18. The method of claim 1 , wherein the method is performed by one or more computing devices.
19. The method of claim 1 , wherein each of the process of performing an aerial image simulation, the process of evaluating the derived image performance parameter value, and the process of adjusting the mask setting values is performed by one or more computing devices.