Controlled hardmask shaping to create tapered slanted fins
Embodiments described herein relate to methods forming optical device structures. One embodiment of the method includes exposing a substrate to ions at an ion angle relative to a surface normal of a surface of the substrate to form an initial depth of a plurality of depths. A patterned mask is disposed over the substrate and includes two or more projections defining exposed portions of the substrate or a device layer disposed on the substrate. Each projection has a trailing edge at a bottom surface contacting the device layer, a leading edge at a top surface of each projection, and a height from the top surface to the device layer. Exposing the substrate to ions at the ion angle is repeated to form at least one subsequent depth of the plurality of depths.
1. A method comprising:
exposing a substrate to ions at an ion angle relative to a surface normal of a surface of the substrate to remove material of the substrate or a device layer disposed on the substrate to form an initial depth of a plurality of depths, wherein a patterned multilayer mask is disposed over the substrate and comprises:
an initial patterned mask disposed over the substrate with two or more initial projections defining exposed portions of the substrate or the device layer disposed on the substrate, each initial projection having a trailing edge at a bottom surface disposed over the substrate; and
at least one subsequent patterned mask with two or more subsequent projections disposed over each initial projection of the initial patterned mask, each subsequent projection includes a leading edge at a top surface of each subsequent projection and a height from the top surface to each initial projection; and
repeating the exposing the substrate to ions at the ion angle to remove material of the substrate or the device layer to form at least one subsequent depth of the plurality of depths in the substrate or the device layer, each subsequent depth that is formed has a subsequent linewidth greater than a preceding linewidth of a preceding depth.
2. The method of claim 1 , wherein the initial patterned mask includes a first material with a first erosion rate and the at least one subsequent patterned mask includes a second material with a second erosion rate.
3. The method of claim 2 , further comprising performing an etch process after the exposing the substrate to ions at the ion angle.
4. The method of claim 3 , wherein the second erosion rate is greater than the first erosion rate based on an etch chemistry of the etch process.
5. The method of claim 2 , wherein the second erosion rate is greater than the first erosion rate when the substrate is exposed to the ions.
6. The method of claim 2 , wherein each subsequent linewidth is controlled by a distance between a leading edge plane of the leading edge and a trailing edge plane of the trailing edge by decreasing the height.
7. The method of claim 1 , wherein the exposing the substrate to ions includes angled ion etching or directional reactive ion etching (RIE).
8. The method of claim 7 , wherein angled ion etching includes generating an ion beam and directing the ion beam at the ion angle to the substrate.
9. The method of claim 1 , wherein the initial patterned mask contacts the device layer.
10. A method comprising:
exposing a device layer disposed over a substrate to ions contacting the device layer at an ion angle relative to a surface normal of a surface of the substrate to remove material of the device layer to form an initial depth of a plurality of depths, wherein a patterned multilayer mask is disposed on the device layer and comprises:
an initial patterned mask disposed on the device layer with two or more initial projections defining exposed portions of the device layer, each initial projection having a trailing edge at a bottom surface contacting the device layer, the initial patterned mask includes a first material with a first erosion rate; and
at least one subsequent patterned mask with two or more subsequent projections disposed over each initial projection of the initial patterned mask, each subsequent projection includes a leading edge at a top surface of each subsequent projection and a height from the top surface to each initial projection, the at least one subsequent patterned mask includes a second material with a second erosion rate greater than the first erosion rate; and
repeating the exposing the device layer to ions contacting the device layer at the ion angle to remove material of the device layer to form at least one subsequent depth of the plurality of depths in the device layer, each subsequent depth that is formed has a subsequent linewidth greater than a preceding linewidth of a preceding depth.
11. The method of claim 10 , wherein the second erosion rate is greater than the first erosion rate when the device layer is exposed to the ions.
12. The method of claim 11 , further comprising performing an etch process after the exposing the device layer to ions the ion angle.
13. The method of claim 12 , wherein the second erosion rate is greater than the first erosion rate based on an etch chemistry of the etch process.
14. The method of claim 10 , wherein each subsequent linewidth is controlled by a distance between a leading edge plane of the leading edge and a trailing edge plane of the trailing edge by decreasing the height.