Superconformal recessed feature fill sol-gels
Various systems and methods relating to a feature fill sol-gel material are provided herein. The feature fill sol-gel material may form a superconformal sol-gel coating. The feature fill sol-gel material may include a first titanium precursor composed of Titanium(IV) and an inorganic ligand. The feature fill sol-gel material may be formed by dissolving or suspending the first titanium precursor in a solvent. The feature fill sol-gel material may be annealed to form the superconformal sol-gel coating. The superconformal sol-gel coating may be an optically transparent coating having an absorbance at a wavelength of 450 nm of less than 0.2% per 150 nm and a refractive index ranging from 1.65 to 2.20.
1. A feature fill sol-gel material for forming a superconformal sol-gel coating, wherein the feature fill sol-gel material comprises a first titanium precursor and a second titanium precursor that is different than the first titanium precursor, wherein the first titanium precursor comprises a titanium oxo mononuclear species and an inorganic ligand,
wherein the feature fill sol-gel material is formed by dissolving or suspending the first titanium precursor in a solvent.
2. The feature fill sol-gel material of claim 1 , wherein the titanium oxo mononuclear species comprises oxy-titanyl.
3. The feature fill sol-gel material of claim 1 , wherein the first titanium precursor comprises an oxo ligand.
4. The feature fill sol-gel material of claim 1 , wherein the inorganic ligand comprises at least one of a sulfate ligand, a phosphate ligand, a selenium oxide ligand, or a tellurium oxide ligand.
5. The feature fill sol-gel material of claim 1 , wherein the solvent comprises at least one of water, propylene glycol, ethylene glycol, lactone, ketone, alcohol, diols acetate or ether.
6. The feature fill sol-gel material of claim 1 , wherein:
the first titanium precursor is Titanium(IV) oxysulfate; and
the second titanium precursor comprises at least one of: Titanium(IV) oxyphosphate, Titanium(IV) oxyacetylacetonate, Titanium (IV) hydroxide, or a multinuclear network of condensed Titanium(IV) hydroxide.
7. The feature fill sol-gel material of claim 1 , wherein the feature fill sol-gel material is annealed to form the superconformal sol-gel coating and the superconformal sol-gel coating comprises an optically transparent coating, wherein the optically transparent coating comprises an absorbance at a wavelength of 450 nm of less than 0.2% per 150 nm and a refractive index ranging from 1.65 to 2.20.
8. The feature fill sol-gel material of claim 1 , wherein the feature fill sol-gel material further comprises one or more of an acid, a base, a peroxide, a surfactant, a cross-linker, a flexibilizer additive, a toughener additive, a polymer, or an additional solvent.
9. A method of producing a superconformal optical coating, the method comprising:
providing a feature fill sol-gel material, wherein forming the feature fill sol-gel material comprises dissolving or suspending a first titanium precursor comprising Titanium(IV) and an inorganic ligand in a solvent;
applying the feature fill sol-gel material onto a substrate comprising a plurality of recessed features; and
annealing the feature fill sol-gel material at an annealing temperature less than 500° C. to form the superconformal optical coating, wherein:
the feature fill sol-gel material fully densifies at the annealing temperature; and
the superconformal optical coating fills the plurality of recessed features without forming voids.
10. The method of claim 9 , wherein the superconformal optical coating has a refractive index equal to or greater than 1.65.
11. The method of claim 9 , wherein the plurality of recessed features comprise a feature width ranging from 1 nm to 300 nm and a feature depth ranging from 1 nm to 2000 nm, and wherein a ratio of the feature depth divided by the feature width is equal or greater than 2.
12. The method of claim 9 , wherein the recessed features comprise one or more of gratings, trenches, vias, or through-holes.
13. The method of claim 9 , wherein applying the feature fill sol-gel material onto the substrate comprises applying the feature fill sol-gel material to form the superconformal optical coating having a final thickness after annealing on a top surface of the substrate of less than 50 nm.
14. The method of claim 9 , wherein applying the sol-gel material onto the substrate comprises spin-coating, dip-coating, spray-coating, ink-jet printing, screen-printing, or contact-printing.
15. The method of claim 9 , wherein:
annealing the feature fill sol-gel material comprises thermally densifying the feature fill sol-gel material to form the superconformal optical coating for a duration less than 10 minutes; and
the superconformal optical coating has a refractive index equal to or greater than 1.65 after annealing.
16. A waveguide, wherein the waveguide comprises:
a substrate, wherein the substrate comprises a plurality of recessed features extending from an outer surface of the substrate to a depth into a bulk of the substrate; and
a superconformal optical coating applied to the substrate, wherein the superconformal optical coating:
is formed from a feature fill sol-gel material comprising a titanium precursor having an oxo-ligand; and
fills the plurality of recessed features, after annealing, without forming voids.
17. The waveguide of claim 16 , wherein the superconformal optical coating comprises a refractive index ranging from 1.65 to 2.20 and an absorption of less than 0.2% per 150 nm of thickness.
18. The waveguide of claim 16 , wherein the superconformal optical coating comprises a thickness on the outer surface of the substrate that is equal to or less than 50 nm.
19. The feature fill sol-gel material of claim 1 , wherein a ratio of the first titanium precursor to the second titanium precursor is from 0.25:1 to 10:1 by weight.
20. The feature fill sol-gel material of 19 , wherein the first titanium precursor is Titanium(IV) oxysulfate and the second titanium precursor is Titanium(IV) oxyacetylacetonate.