Pressure Sensor Hermetic Seal Trench Barrier
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Solution Overview
Problem
Pressure sensors experience high pressure error drift due to poor hermetic sealing at the fusion bond interface, leading to gas effects that cause changes in cavity pressure and errors over time, despite the use of oxide layers which only partially mitigate this issue.
Innovation Solution
The implementation of a trench isolated by a barrier layer, such as silicon nitride or metal, within the membrane and oxide structure to enhance hermetic sealing, combined with a high-density dielectric material coating on the lateral walls of the cavity, to further reduce gas effects and improve the seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxide layer is used to reduce gas effect, then hermeticity is improved, but gas effect still occurs due to poor hermetic sealing at the fusion bond interface
Solution Approach 1:
The patent applies composite materials by combining multiple barrier layers with different properties: a first barrier layer (metal or dense dielectric) and a second barrier layer (oxide layer) are used together. The first barrier layer provides primary hermetic sealing at the fusion bond interface, while the second oxide layer provides additional protection. This composite structure addresses the limitation of using only oxide layers by creating a multi-layered defense against gas penetration, thereby improving both hermeticity and pressure measurement precision.
2Reliability
If a trench is formed in the oxide layer to isolate the cavity, then hermetic seal is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by forming a trench that divides and isolates the pressure-sensitive cavity from the surrounding oxide layer. This trench creates a physical separation that prevents gas migration pathways, effectively segmenting the structure into isolated regions. The trench acts as a barrier that breaks potential gas leakage paths, thereby improving hermetic sealing despite the added structural complexity.
3Measurement precision
If lateral walls of the cavity are coated with barrier layer, then gas effect is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by selectively coating only the lateral walls of the cavity with barrier layers, rather than coating the entire sensor structure. The first and second barrier layers are applied specifically to the inner lateral walls where gas effect is most problematic. This localized approach provides targeted protection against gas penetration at the most critical interfaces while avoiding unnecessary coating of other areas, thus reducing manufacturing complexity compared to full-structure coating.
Data Source
AI summary
A sensor includes a substrate, an oxide layer, a membrane, an electrode, and a trench. The oxide layer is disposed on the substrate. The membrane is positioned on the oxide layer. The membrane with the oxide layer and the substrate forms an enclosed cavity therein. The membrane comprises a rigid portion and a deformable portion wherein the deformable portion of the membrane deforms responsive to stimuli. The oxide layer forms side walls of the cavity. The electrode is positioned on the substrate and within the cavity. The trench is formed in the oxide layer, and wherein the trench is covered with barrier material.