MEMS Eutectic Sealing Structure for Tunable Cavity Pressure
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Solution Overview
Problem
Existing MEMS devices face challenges in sealing chambers due to micro leaks caused by metal grain growth and limited tunability of cavity pressure, constrained by critical dimensions and etching limitations, which affect their performance and application range.
Innovation Solution
Employing a eutectic sealing structure with a first and second metal layer bonded eutectically to seal through holes in MEMS devices, allowing for wider etching windows and tunable cavity pressure through annealing, thereby enhancing airtightness and pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal sealing structures are used, then manufacturing process is simple, but micro leaks occur due to metal grain growth and sealing performance deteriorates
Solution Approach 1:
The patent employs a composite sealing structure consisting of a first metal layer and a second metal layer with different material compositions. The first metal layer provides initial sealing, while the second metal layer forms a eutectic alloy with the first layer to create a low-melting-point eutectic region that fills and seals micro-leak paths, thereby improving overall sealing performance and preventing micro leaks caused by metal grain growth.
2Adaptability or versatility
If conventional sealing structures are used, then manufacturing process is straightforward, but cavity pressure tunability is limited
Solution Approach 1:
The patent utilizes the eutectic reaction temperature as a controllable parameter to achieve cavity pressure tunability. By controlling the annealing temperature during the eutectic sealing process, the melting and solidification behavior of the eutectic alloy can be adjusted, which in turn allows for precise control of cavity pressure. This enables the sealing structure to adapt to different pressure requirements without significantly increasing device complexity.
3Reliability
If through holes are sealed to prevent micro leaks, then sealing performance improves, but etching window becomes constrained by critical dimensions
Solution Approach 1:
The patent divides the sealing process into multiple stages: first forming a initial metal layer seal, then adding a second metal layer that reacts to form a eutectic alloy. This segmentation allows the etching process to be performed in wider windows without compromising final sealing quality, as the multi-layer eutectic structure provides redundant sealing paths that compensate for variations in etching precision.
4Reliability
If eutectic sealing structure is implemented, then micro leaks are prevented and sealing performance improves, but manufacturing process complexity increases
Solution Approach 1:
The patent performs preliminary actions by pre-forming the first metal layer with specific composition and thickness before adding the second metal layer. The first layer is prepared in advance to ensure proper eutectic reaction occurs when the second layer is deposited and annealed. This preliminary preparation simplifies the overall manufacturing process by establishing a controlled foundation that guides subsequent processing steps, reducing the complexity burden of the eutectic sealing approach.
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 eutectic sealing structure effectively prevents micro leaks and enables tunable cavity pressure, improving the reliability and versatility of MEMS devices by overcoming etching limitations and enhancing sealing performance.
Implementation Method 1
a first metal layer and a second metal layer which are bonded eutectically to one another
Implementation Method 2
allowing for wider etching windows and tunable cavity pressure through annealing
Data Source
AI summary
A method for manufacturing a semiconductor structure is provided. The method includes the operations as follows. A first substrate having a top surface is received. A semiconductor layer is formed over the first substrate. A cavity is formed at the top surface of the semiconductor layer. A second substrate is bonded over the first substrate to cover the semiconductor layer. The second substrate has a through hole connected to the cavity of the semiconductor layer. A eutectic sealing structure is formed on the second substrate to cover the through hole. The eutectic sealing structure includes a first metal layer and a second metal layer eutectically bonded on the first metal layer.