Method and system for tunable gradient patterning using a shadow mask

1. A method of depositing a variable thickness material, the method comprising:

providing a substrate comprising a uniform diffractive structure including a plurality of diffractive elements;

providing a shadow mask having a first region with a first aperture dimension to aperture periodicity ratio and a second region with a second aperture dimension to aperture periodicity ratio less than the first aperture dimension to aperture periodicity ratio;

positioning the shadow mask adjacent the substrate; and

performing a deposition process on the substrate to deposit the variable thickness material, wherein a layer thickness adjacent the first region is greater than a layer thickness adjacent the second region.

2. The method of claim 1 wherein the substrate comprises SiO 2 .

3. The method of claim 2 wherein the uniform diffractive structure comprises a diffraction grating.

4. The method of claim 1 wherein the variable thickness material comprises a conformal layer.

5. The method of claim 1 wherein:

the shadow mask comprises a plurality of apertures and a surface parallel to the plurality of apertures;

the substrate comprises a deposition surface; and

positioning the shadow mask adjacent the substrate comprises placing the surface of the shadow mask parallel to the deposition surface.

6. The method of claim 1 wherein the shadow mask is characterized by a varying aperture dimension to aperture periodicity ratio in two directions.

7. The method of claim 1 wherein the variable thickness material is characterized by a first diffractive element depth in the first region and a second diffractive element depth less than the first diffractive element depth in the second region.

8. The method of claim 1 wherein the variable thickness material is characterized by a first diffractive element width in the first region and a second diffractive element width less than the first diffractive element width in the second region.

9. The method of claim 1 wherein performing the deposition process on the substrate comprises a plasma deposition process.

10. A method of fabricating a master substrate, the method comprising:

providing a shadow mask having:

a first region characterized by a first gradient aperture dimension to aperture periodicity ratio in at least a first direction; and

a second region characterized by a second gradient aperture dimension to aperture periodicity ratio in at least a second direction;

providing a substrate having:

a mask characterized by diffractive features;

a first exposed region; and

a second exposed region;

positioning the shadow mask adjacent the substrate, wherein the first region is aligned with the first exposed region and the second region is aligned with the second exposed region;

exposing the substrate to at least one of a plasma coating or a deposition process;

coating first diffractive elements adjacent the first region, wherein the first diffractive elements are characterized by a first gradient depth and first line width profile in the at least a first direction; and

coating second diffractive elements adjacent the second region, wherein the second diffractive elements are characterized by a second gradient depth and second line width profile in the at least a second direction.

11. The method of claim 10 wherein the first gradient depth is greater than the second gradient depth.

12. The method of claim 10 wherein the first line width profile is characterized by a first width and the second line width profile is characterized by a second width less than the first width.

13. The method of claim 10 wherein:

the first region is further characterized by a third gradient aperture dimension to aperture periodicity ratio in at least a direction orthogonal to the first direction;

the second region is further characterized by a fourth gradient aperture dimension to aperture periodicity ratio in at least a direction orthogonal to the second direction;

the first diffractive elements are further characterized by a third gradient depth profile in the direction orthogonal to the first direction; and

the second diffractive elements are further characterized by a fourth gradient depth profile in the direction orthogonal to the second direction.

14. The method of claim 10 wherein:

the first gradient aperture dimension to aperture periodicity ratio is equal to the second gradient aperture dimension to aperture periodicity ratio; and

the first direction and the second direction are a same direction.

15. The method of claim 10 wherein:

the first gradient aperture dimension to aperture periodicity ratio is defined by a constant center-to-center spacing of apertures and a graded aperture dimension along the first direction; and

the second gradient aperture dimension to aperture periodicity ratio is defined by a constant center-to-center spacing of apertures and a graded aperture dimension along the second direction.

16. The method of claim 10 wherein:

the first gradient aperture dimension to aperture periodicity ratio is defined by a constant aperture dimension along the first direction and a graded center-to-center spacing of apertures; and

the second gradient aperture dimension to aperture periodicity ratio is defined by a constant aperture dimension along the second direction and a graded center-to-center spacing of apertures.

17. The method of claim 10 wherein the substrate comprises a silicon substrate.

18. The method of claim 10 wherein the substrate comprises a diffractive structure including a diffraction grating.

19. The method of claim 18 wherein the deposition process comprises a plasma deposition process.

20. The method of claim 10 wherein the substrate comprises a conformal layer.