Electrical Feedthrough With Annular Isolation Trench
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Solution Overview
Problem
Existing methods for producing electrical feedthroughs in substrates face challenges such as interference from metal in micromechanical components, difficulty in handling high voltages, and limitations in achieving low volume resistance and high dielectric strength due to rough surfaces and inelastic properties of metals.
Innovation Solution
The method involves creating an annular isolation trench around the electrical feedthrough, which is closed off on both sides, allowing for metal plating with low leakage currents, low parasitic capacitance, and high mechanical robustness, eliminating the need for diffusion barriers and seed layers, and enabling adjustable dielectric strength through geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a narrow through hole is filled with metal to achieve low volume resistance, then electrical conductivity is improved, but metal interference occurs in voltage-sensitive components
Solution Approach 1:
The feedthrough structure is segmented into multiple functional layers: a conductive core for electrical connection, surrounded by an insulating layer, which is then enclosed by a mechanically robust sealing layer. This segmentation allows the conductive function to be separated from the mechanically sensitive region, eliminating metal interference while maintaining electrical conductivity.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the metal conductive core and the substrate. This intermediary layer prevents direct contact between metal and voltage-sensitive components, eliminating metal interference effects such as hysteresis and voltage transmission while maintaining the electrical feedthrough function.
2Reliability
If oxide deposition is used to insulate through holes for high voltage handling, then dielectric strength is improved, but the rough surface reduces achievable oxide thickness and dielectric strength
Solution Approach 1:
The insulating layer is deposited beforehand to create a smooth base layer that fills and levels the rough surface of the etched through hole. This preliminary smoothing action enables subsequent oxide deposition to achieve greater thickness and higher dielectric strength without being limited by the underlying surface roughness.
Solution Approach 2:
The insulation system uses a composite structure combining an insulating layer (such as polymer or glass) with an oxide layer. The insulating layer compensates for surface roughness and provides a smooth foundation, while the oxide layer provides the primary dielectric strength for high voltage handling.
3Reliability
If the through hole is completely filled with metal, then volume resistance is reduced, but metal interference and mechanical stress increase
Solution Approach 1:
The feedthrough structure is segmented into multiple functional layers: a conductive core for electrical connection, surrounded by an insulating layer, which is then enclosed by a mechanically robust sealing layer. This segmentation allows the conductive function to be separated from the mechanically sensitive region, eliminating metal interference while maintaining electrical conductivity.
Solution Approach 2:
Metal is placed only in the local region where electrical conductivity is required (the conductive core), while the surrounding regions use insulating and sealing materials. This localized metal placement achieves the necessary low volume resistance while minimizing metal interference with voltage-sensitive components.
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
This approach results in electrical feedthroughs with low volume resistance, high mechanical robustness, and adjustable dielectric strength, reducing interference and enhancing the reliability of voltage-sensitive components like pressure sensors.
Implementation Method 1
the through hole is then completely or partially filled with a metal or a metal alloy
Data Source
AI summary
A method is described for producing an electrical feedthrough in a substrate, and a substrate having an electrical feedthrough. The method has the following operations of forming the electrical feedthrough so that it extends through the substrate from the front side to the back side of the substrate, forming a first closing layer on a front side of the substrate, forming an annular isolation trench in the substrate which encloses the electrical feedthrough, using an etching process starting from the back side of the substrate, the etching process terminating at the first closing layer, and closing off the annular isolation trench in the substrate by forming a second closing layer on the back side of the substrate.