Micromechanical Sensor Metallic Bonding and Sacrificial Layer Etching
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Solution Overview
Problem
Existing micromechanical inertial sensors face challenges in achieving well-defined electrode spacing and low parasitic capacitances due to liquid phase bonding methods, leading to process scatter and reduced yield, and struggle to maintain stable internal pressures and large cavern volumes.
Innovation Solution
A micromechanical sensor is produced using a first substrate with a mechanical functional layer, a sacrificial layer, and an electrode device, connected to a second and third substrate via metallic bond connections, allowing precise electrode spacing and low surface roughness demands, with etch stop layers preventing underetching and cavities for pressure compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If liquid phase bonding method is used, then bonding process is simplified, but electrode spacing becomes poorly defined and process scatter increases
Solution Approach 1:
The patent applies preliminary action by depositing sacrificial layers and electrodes on the substrate before bonding. This allows the electrode spacing to be precisely defined by the deposited layer thickness, and the bonding to occur after the precise structures are already in place, thus resolving the contradiction between ease of manufacture and manufacturing precision
Solution Approach 2:
The patent uses sacrificial layers as intermediary elements that are deposited precisely, then removed after bonding to create cavities. These sacrificial layers act as mediators that enable both precise electrode spacing definition and subsequent cavity formation, resolving the contradiction between bonding simplicity and spacing precision
2Ease of manufacture
If conventional bonding methods are used, then production is simplified, but surface roughness requirements increase and yield decreases
Solution Approach 1:
The patent performs preliminary deposition of sacrificial layers and electrodes before bonding, creating robust structures that are less sensitive to surface roughness during bonding. This preliminary structuring allows conventional bonding methods to achieve higher yields by reducing the criticality of surface preparation
Solution Approach 2:
The patent provides beforehand cushioning by creating sacrificial layers that absorb bonding imperfections and surface irregularities. These sacrificial structures cushion against the effects of surface roughness, allowing bonding to proceed with relaxed surface requirements while maintaining high yield
3Volume of moving object
If small cavern volumes are used, then device size is reduced, but internal pressure increases and stability decreases
Solution Approach 1:
The patent applies preliminary action by depositing thick sacrificial layers before bonding, which after removal create large cavern volumes. This preliminary deposition enables the formation of large cavities that can accommodate pressure changes, resolving the contradiction between small device size and pressure stability
Solution Approach 2:
The patent changes the parameter of cavern volume by using controlled deposition of sacrificial layers to create optimally sized cavities. By adjusting the sacrificial layer thickness, the patent optimizes the balance between device compactness and internal pressure stability, allowing large enough caverns to maintain pressure while keeping the overall device size manageable
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 enhances detection quality, reduces process scatter, increases yield, and maintains stable internal pressures, enabling precise capacitive measurements and efficient production of sensitive inertial components.
Implementation Method 1
a well-defined open space is advantageously fashioned underneath the movable MEMS elements, and unintentional underetching of the wiring layers is avoided
Implementation Method 2
the first substrate is connected to the second and third substrates by mechanical bond connections
Implementation Method 3
the sacrificial layer and the electrode device are fashioned by a layer deposition
Data Source
AI summary
A micromechanical sensor includes a base substrate, a cap substrate, and a MEMS substrate that is connected to each of the base and cap substrates by respective metallic bond connections and that includes a mechanical functional layer including movable MEMS elements, an electrode device for acquiring an indication of a movement of the MEMS elements and fashioned by layer deposition, and a sacrificial layer that is lower than the mechanical function layer, is fashioned by layer deposition, and is omitted in a region underneath the movable MEMS elements.