Process for making a metallic grating

Patent metadata

Field	Value
Publication number	US-11733439-B2
Application number	US-202217972816-A
Country	US
Kind code	B2
Filing date	Oct 25, 2022
Priority date	Sep 17, 2012
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

A metallic grating is formed to include a substrate; 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; a metallic superconformal filling formed and disposed in the high aspect ratio trenches; and a grating including a spatial arrangement of the high aspect ratio trenches that are filled with the metallic superconformal filling such that the metallic superconformal filling is void-free, and the high aspect ratio trenches are bottom-up filled with the metallic superconformal filling, wherein a height of the metallic superconformal filling is less than or equal to the height of the high aspect ratio trenches.

First claim

What is claimed is:

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(SO 3 ) 2 3− anions as a source of gold that is superconformally deposited as the metallic superconformal filling in the high aspect ratio trenches;
a plurality of SO 3 2− anions; and
a plurality of Bi 3+ cations as a brightener and an accelerator for superconformally depositing gold in the high aspect ratio trenches;

convectively transporting the Au(SO 3 ) 2 3− anions and the Bi 3+ 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(SO 3 ) 2 3− 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.

2. The process of claim 1 , wherein the process is performed in an absence of through-mask plating.

3. The process of claim 1 , wherein the metallic grating comprises:
the substrate;
the plurality of high aspect ratio trenches disposed in the substrate such that the high aspect ratio trenches are spaced apart from one another by the field surface of the substrate;
the metallic superconformal filling formed and disposed in the high aspect ratio trenches; and
a grating comprising a spatial arrangement of the high aspect ratio trenches that are filled with the metallic superconformal filling such that the metallic superconformal filling is void-free, and the high aspect ratio trenches are bottom-up filled with the metallic superconformal filling,
wherein an aspect ratio of the high aspect ratio trenches is from 0.5 to 200, and a height of the high aspect ratio trenches is from 50 nm to 5 mm, and a height of the metallic superconformal filling is less than or equal to the height of the high aspect ratio trenches.

4. A process for making a diffraction grating, the process comprising:
providing a wafer comprising a plurality of high aspect ratio trenches disposed in silicon, wherein the high aspect ratio trenches comprise a depth from 1 μm deep to 1 mm deep with respect to a field surface of the wafer and an aspect ratio from 10 to 200;
forming a conductive seed layer on the high aspect ratio trenches, the seed layer comprising: 10 nm to 100 nm of platinum grown over exposed sidewalls and bottom members of the high aspect ratio trenches and followed by forming an overlying Au layer formed on the platinum;
contacting the high aspect ratio trenches with a superconformal filling composition comprising from 40 mmol/L to 320 mmol/L Na 3 Au(SO 3 ) 2 and from 0.1 mol/L to 1.0 mol/L Na 2 SO 3 , wherein a pH of the superconformal filling composition if from 8.0 to 10.0;
providing Bi 3+ to the superconformal filling composition;
contacting the high aspect ratio trenches with the Bi 3+ ;
rotating the wafer in the superconformal filling composition at a rotation rate from 100 RPM to 2000 RPM;
subjecting the high aspect ratio trenches to a deposition potential relative to a Hg/Hg 2 SO 4 /saturated K 2 SO 4 reference electrode from −0.6 V to −0.85 V; and
superconformally filling the high aspect ratio trenches such that superconformal filling is bottom-up with upward growth forming a metallic superconformal filling comprising gold at the deposition potential relative to a Hg/Hg 2 SO 4 /saturated K 2 SO 4 reference electrode from −0.6 V to −0.85 V; and
automatically passivating a growth front of the high aspect ratio trenches from 10 minutes to 1 week after beginning of forming the metallic superconformal filling in the high aspect ratio trenches to make the diffraction grating.

5. The process of claim 4 , wherein the diffraction grating comprises:
the wafer, and the wafer is a substrate for the diffraction grating;
the plurality of high aspect ratio trenches disposed in the substrate such that the high aspect ratio trenches are spaced apart from one another by the field surface of the substrate;
the metallic superconformal filling formed and disposed in the high aspect ratio trenches; and
a grating comprising a spatial arrangement of the high aspect ratio trenches that are filled with the metallic superconformal filling such that the metallic superconformal filling is void-free, and the high aspect ratio trenches are bottom-up filled with the metallic superconformal filling,
wherein an aspect ratio of the high aspect ratio trenches is from 0.5 to 200, and a height of the high aspect ratio trenches is from 50 nm to 5 mm, and a height of the metallic superconformal filling is less than or equal to the height of the high aspect ratio trenches.

6. A process for superconformally filling a recessed feature of an article with gold, the process comprising:
providing the article comprising:
a substrate;
a field surface disposed on the substrate;
the recessed feature disposed on the substrate and surrounded by the field surface, the recessed feature comprising:
a bottom member;
a sidewall that separates the bottom member from the field surface,
the recessed feature having an aspect ratio of a depth to a width from 0.5 to 200 before superconformally filling the recessed feature, the aspect ratio decreasing during superconformally filling the recessed feature; and

an overlayer disposed on the article such that the field surface and the recessed feature are fully metallized for contact with a superconformal filling composition;
contacting the field surface and the recessed feature with the superconformal filling composition, the superconformal filling composition having a near-neutral pH and comprising:
a plurality of Au(SO 3 ) 2 3− anions as a source of gold for superconformally depositing gold in the recessed feature;
a plurality of SO 3 2− anions; and
a plurality of Bi 3+ cations as a brightener and an accelerator for superconformally depositing gold in the recessed feature;

convectively transporting the Au(SO 3 ) 2 3− anions and the Bi 3+ cations to the bottom member by actively moving the substrate relative to the superconformal filling composition;
subjecting the field surface and the recessed feature to an electrical current to superconformally deposit gold from the Au(SO 3 ) 2 3− anions on the bottom member relative to the sidewall and the field surface, the electrical current providing a cathodic voltage (V SSE ) from −0.6 V to −1.0 V relative to a satu

Assignees

• Government Of The Us Secretary Of Commerce

Inventors

• Josell Daniel
• Moffat Thomas Polk

Classifications

• G02B5/1852 Primary

  using mechanical means, e.g. ruling with diamond tool, moulding · CPC title

• G02B5/1809

  with pitch less than or comparable to the wavelength · CPC title

• G02B5/1857 Primary

  using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams · CPC title

• G02B5/1861

  Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials (G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence) · CPC title