Patterning of high refractive index glasses by plasma etching
Plasma etching processes for forming patterns in high refractive index glass substrates, such as for use as waveguides, are provided herein. The substrates may be formed of glass having a refractive index of greater than or equal to about 1.65 and having less than about 50 wt % SiO 2 . The plasma etching processes may include both chemical and physical etching components. In some embodiments, the plasma etching processes can include forming a patterned mask layer on at least a portion of the high refractive index glass substrate and exposing the mask layer and high refractive index glass substrate to a plasma to remove high refractive index glass from the exposed portions of the substrate. Any remaining mask layer is subsequently removed from the high refractive index glass substrate. The removal of the glass forms a desired patterned structure, such as a diffractive grating, in the high refractive index glass substrate.
1. A method of forming an optical waveguide structure, the method comprising:
identifying desired dimensional characteristics of first features to be formed in a high-index glass substrate, wherein the high-index glass substrate has a refractive index of about 1.65 or greater;
identifying etching characteristics of an etching process that is used for forming at least the first features in the high-index glass substrate;
determining, based on the identified etching characteristics, biased dimensional characteristics of second features of a patterned layer that is to be formed on the high-index glass substrate prior to forming the first features in the high-index glass substrate;
forming the patterned layer on the high-index glass substrate, the forming including forming the second features in the patterned layered, the second features having the biased dimensional characteristics; and
transferring, using the etching process, a pattern of the second features, having the biased dimensional characteristics, into the high-index glass to form the first features, having the desired dimensional characteristics in the high-index glass substrate.
2. The method of claim 1 , wherein the biased dimensional characteristics of the second features are larger than the desired dimensional characteristics of the first features.
3. The method of claim 1 , wherein the first features comprise openings of a desired size in the high-index glass substrate.
4. The method of claim 1 , further comprising removing the patterned layer from the high-index glass substrate.
5. The method of claim 4 , wherein the patterned layer is removed by an ashing process and/or a wet etch process.
6. The method of claim 1 , further comprising:
forming an initial patterned layer on the high-index glass substrate, the forming including forming third features in the initial patterned layer, the third features having initial biased dimensional characteristics; and
subsequently forming the patterned layer on the high-index glass substrate, wherein the second features of the patterned layer are disposed over the third features of the initial patterned layer.
7. The method of claim 6 , wherein the biased dimensional characteristics of second features are larger than the initial biased dimensional characteristics of third features.
8. The method of claim 6 , wherein the patterned layer on the high-index glass substrate is conformally formed over the initial patterned layer.
9. The method of claim 8 , wherein the patterned layer is formed by a vapor deposition process and/or a chemical vapor deposition process.
10. The method of claim 6 , wherein the patterned layer on the high-index glass substrate is chemically formed over the initial patterned layer.
11. The method of claim 10 , wherein the patterned layer is formed by oxidation of the initial patterned layer.
12. A method for patterning a glass substrate, the method comprising:
providing an etch mask over a glass substrate formed of glass having a refractive index of 1.65 or greater, wherein features in the etch mask for defining corresponding features in the glass substrate are larger than a desired size of the corresponding features; and
etching the glass substrate through the etch mask to define the features in the glass substrate.
13. The method of claim 12 , wherein providing the etch mask comprises:
forming an initial etch mask; and
increasing a size of features of the initial etch mask to form the etch mask.
14. The method of claim 13 , wherein the etch mask comprises resist and wherein forming the initial etch mask comprises imprinting the resist.
15. The method of claim 13 , wherein increasing the size of features of the initial etch mask comprises depositing a conformal film on the initial etch mask.
16. The method of claim 12 , wherein the glass substrate comprises less than about 50 wt % SiO 2 and wherein more than 50 wt % of the glass substrate is formed of one or more of B 2 O 3 , Al 2 O 3 , ZrO 2 , Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO, BaO, ZnO, La 2 O 3 , Nb 2 O 5 , TiO 2 , HfO, and Sb 2 O 3 .
17. The method of claim 12 , wherein the etch mask comprises a carbon-based polymer, chromium, or silicon oxide.
18. The method of claim 12 , wherein etching the glass substrate comprises performing ion beam milling to remove material of the glass substrate.
19. The method of claim 18 , wherein etching the glass substrate forms an opening having a depth of 50 nm or more in less than 20 seconds.
20. The method of claim 19 , wherein etching the glass substrate forms the opening in less than 10 seconds.