Liquid Alloy Capillary Connections for Sub-10 μm Microelectronics
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Solution Overview
Problem
Existing methods struggle to produce electrically conductive connections with dimensions of 100 μm or less, particularly due to high surface tension and oxide layer formation in liquid metals, which hinder wettability and uniform material flow on substrates, leading to breaks in electrical conductivity.
Innovation Solution
A method involving a capillary with a metallic surface to penetrate an insulating-layered reservoir of liquid alloy and apply it to a substrate, forming an electrically conductive connection by adhesion, while the oxide layer forms a passivating barrier to prevent deliquescence and enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid metal is applied directly to substrate using conventional methods, then material can be deposited, but wettability is poor due to high surface tension and oxide layer formation
Solution Approach 1:
The patent introduces an intermediary substance (organic solvent or chelating agent) that mediates between the liquid metal and substrate. This intermediary reduces surface tension and improves wettability by forming a temporary interface layer, allowing the liquid metal to spread uniformly without direct contact issues between the metal and substrate.
Solution Approach 2:
The patent changes physical parameters of the liquid metal system by controlling oxide layer thickness, adjusting surface tension through chemical additives, and modifying application parameters (temperature, pressure, flow rate) to achieve optimal wettability and electrical conductivity simultaneously.
2Ease of manufacture
If oxide layer is removed using acid to improve wettability, then adhesion may improve, but processing difficulty increases and uniform flow is hindered
Solution Approach 1:
The patent converts the harmful oxide layer into a beneficial thin protective layer by controlling its formation rather than complete removal. The oxide layer is maintained at optimal thickness to provide both adhesion promotion and protection against excessive oxidation, eliminating the need for complex acid treatment processes.
Solution Approach 2:
Instead of completely removing the oxide layer (excessive action), the patent applies partial action by controlling oxide layer thickness to an optimal level that provides sufficient adhesion while maintaining liquid metal flow properties and electrical conductivity.
3Length of moving object
If connection dimensions are reduced below 100 μm for miniaturization, then device size decreases, but electrical conductivity reliability deteriorates due to breaks and interruptions
Solution Approach 1:
The patent changes material parameters by using eutectic alloys with lower melting points and adjusted compositions that maintain liquid state at operating temperatures, ensuring uniform flow and complete filling of sub-100 μm connections without breaks or interruptions, thereby maintaining electrical conductivity reliability at miniaturized dimensions.
4Productivity
If liquid metal flow is increased to ensure material supply, then connection formation improves, but processing uniformity deteriorates due to stringy behavior from oxide layer
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid metal alloy and controls oxide layer thickness to optimize the balance between material flow rate and processing uniformity. By adjusting alloy composition and oxide layer characteristics, the system achieves sufficient material supply while preventing stringy behavior and ensuring uniform connection formation.
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
Enables reliable production of electrically conductive connections with resolutions below 10 μm, reducing parasitic capacitances and allowing immediate ohmic contact without requiring additional processing steps, thus overcoming limitations of prior art in miniaturization.
Implementation Method 1
providing a capillary configured for taking up the electrically conductive liquid alloy; penetrating of a tip of the capillary under the surface of the reservoir and taking up of a portion of the alloy from the reservoir
Implementation Method 2
an occurrence of a high surface tension of the liquid alloys comprising gallium as a constituent and, secondly, a formation of an oxide layer on the surface of the liquid alloy
Implementation Method 3
applying the portion of the alloy to the substrate in such a manner that an electrically conductive connection is formed from the alloy on the substrate, wherein the alloy remains on the substrate by adhesion
Data Source
AI summary
The invention relates to a method (110) for producing an electrically conductive connection (112, 112′) on a substrate (114), comprising the following steps:a) providing a substrate (114), wherein the substrate (114) is configured for receiving an electrically conductive connection (112, 112′);b) providing a reservoir of an electrically conductive liquid alloy, wherein the reservoir has a surface at which the alloy has an insulating layer;c) providing a capillary (120) configured for taking up the electrically conductive liquid alloy;d) penetrating of a tip (122) of the capillary (120) under the surface of the reservoir and taking up of a portion of the alloy from the reservoir; ande) applying the portion of the alloy at least partly to the substrate (114) in such a manner that an electrically conductive connection (112, 112′) is formed from the alloy on the substrate (114), wherein the alloy remains on the substrate (114) by adhesion.The invention furthermore relates to a method for producing a microelectronic device (124) and to a microelectronic device (124), in particular a transistor (130).