CPC G02B 5/1852 (2013.01) [G02B 5/1809 (2013.01); G02B 5/1857 (2013.01)] | 16 Claims |
1. A process for making a metallic grating, the process comprising:
providing a substrate with a plurality of high aspect ratio trenches disposed in the substrate such that the high aspect ratio trenches are spaced apart from one another by a field surface of the substrate, and each of the high aspect ratio trenches comprising:
a bottom member;
a sidewall that separates the bottom member from the field surface,
an aspect ratio of a depth to a width from 0.5 to 200 before filling the high aspect ratio trench with a metallic superconformal filling, the aspect ratio decreasing during filling the high aspect ratio trench with the metallic superconformal filling; and
an overlayer disposed on the bottom member;
contacting the overlayer on the bottom member with a superconformal filling composition, the superconformal filling composition having a near-neutral pH and comprising:
a plurality of Au(SO3)23− anions as a source of gold that is superconformally deposited as the metallic superconformal filling in the high aspect ratio trenches;
a plurality of SO32− anions; and
a plurality of Bi3+ cations as a brightener and an accelerator for superconformally depositing gold in the high aspect ratio trenches;
convectively transporting the Au(SO3)23− anions and the Bi3+ cations to the bottom member by actively moving the substrate relative to the superconformal filling composition;
subjecting the bottom member of the high aspect ratio trenches to an electrical current to superconformally deposit gold from the Au(SO3)23− anions on the bottom member relative to the sidewall and the field surface, the electrical current providing a cathodic voltage, and a first deposition ratio of a first deposition rate of gold on the bottom member relative to a second deposition rate of gold on the sidewall; and
increasing the electrical current subjected to the field surface and the high aspect ratio trenches to maintain the cathodic voltage during superconformally depositing gold in the high aspect ratio trenches to form the metallic superconformal filling comprising gold in the high aspect ratio trenches such that the metallic superconformal filling is void-free and seam-free.
|