Gold Metallization in High Aspect Ratio Trenches
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Solution Overview
Problem
Conventional processes for depositing gold in high aspect ratio trenches often result in voids and seams, leading to inefficient filling and increased post-deposition processing time, and typically use cyanide or lead additives and polymer additives, which are environmentally harmful.
Innovation Solution
A process for superconformally filling high aspect ratio trenches with gold using a near-neutral pH electrolyte containing Au(SO3)2− anions and Bi3+ cations, where the substrate is moved relative to the electrolyte to convectively transport the ions and an electrical current is applied to deposit gold cathodically, minimizing deposition on the field surface and ensuring a void-free and seam-free filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional gold deposition processes are used in high aspect ratio trenches, then gold can be deposited, but voids and seams form leading to defective filling
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by replacing cyanide-based gold complexes with sulfite-based gold complexes (Au(SO3)2−), and adjusting the pH to near-neutral conditions. These parameter changes fundamentally alter the deposition mechanism to achieve void-free, seam-free filling in high aspect ratio trenches, resolving the quality and reliability contradiction.
2Productivity
If conventional deposition processes are used, then gold deposition can occur, but post-deposition processing time increases due to voids and seams requiring correction
Solution Approach 1:
The patent performs preliminary action by optimizing the electrolyte composition and deposition parameters before the actual deposition occurs. The near-neutral pH sulfite-based electrolyte with Bi3+ cations is prepared in advance to ensure proper wetting and conformal deposition, preventing defects that would require later correction and thus reducing post-deposition processing time.
3Ease of manufacture
If cyanide or lead additives and polymer additives are used in gold deposition, then deposition can proceed, but environmental harm increases
Solution Approach 1:
The patent converts the potentially harmful cyanide-based system into a beneficial sulfite-based system. By replacing toxic cyanide additives with environmentally friendly sulfite complexes and near-neutral pH conditions, the process maintains good deposition processability while eliminating environmental harm, thus resolving this contradiction.
4Quantity of substance
If gold deposition occurs on the field surface, then more gold is deposited, but waste increases and processing complexity increases
Solution Approach 1:
The patent applies local quality by creating different deposition conditions in different regions. The near-neutral pH sulfite-based electrolyte with Bi3+ cations provides selective wetting and deposition behavior, promoting gold deposition primarily in the trench regions while suppressing deposition on the field surface. This local differentiation reduces gold waste and simplifies processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process achieves defect-free, void-free, and seam-free gold metallization with reduced waste and processing time, using environmentally friendly conditions without cyanide, lead, or polymer additives, and allows for the formation of metallic superconformal fillings suitable for applications like diffraction gratings and microelectronics.
Implementation Method 1
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
Implementation Method 2
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
Data Source
AI summary
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.