Sub-wavelength diffractive elements to reduce corner rounding
The present invention discloses a mask including: a first region near a corner of a feature, the first region including a first element, the first element being transparent to a light, the first element having a side that is smaller than a wavelength of said light; a second region near the corner of the feature, the second region including a second element, the second element being transparent to the light, the second element having a side that is smaller than the wavelength of the light; and a third region near the corner of the feature, the third region including a third element, the third element being opaque to the light, the third element having a side that is smaller than the wavelength of the light.
1. A method comprising:
forming a first region of a mask near a corner of a feature, said first region comprising a first element, said first element being transparent to a light, said first element having a side that is smaller than a wavelength of said light;
forming a second region of said mask near said corner of said feature, said second region comprising a second element, said second element being translucent to said light, said second element having a side that is smaller than said wavelength of said light; and
forming a third region of said mask near said corner of said feature, said third region comprising a third element, said third element being opaque to said light, said third element having a side that is smaller than said wavelength of said light;
wherein said first element, said second element, and said third element each has a square shape.
2. The method of claim 1 wherein said first element comprises a phase of zero degree or 180 degrees.
3. The method of claim 1 wherein said second element comprises a phase of zero degree or 180 degrees.
4. The method of claim 1 wherein said first element comprises a transmittance of 95-99%.
5. The method of claim 1 wherein said second element comprises a transmittance of 5-15%.
6. The method of claim 1 wherein said third element comprises a transmittance of 0-1%.
7. The method of claim 1 wherein said first element, said second element, and said third element have a uniform shape.
8. The method of claim 1 wherein said first element, said second element, and said third element have a uniform size.
9. The method of claim 1 wherein said first element, said second element, and said third element have discrete states.
10. The method of claim 1 wherein said first element is surrounded by 8 neighboring elements.
11. The method of claim 1 wherein said wavelength of light comprises 193 nanometers.
12. The method of claim 1 wherein said side comprises 35-70% of said wavelength of said light.
13. The mask method of claim 1 wherein said side comprises ½ of said wavelength of said light.
14. The method of claim 1 wherein said side comprises 90-110 nm.