Monocrystalline Pressure Sensor Crystal Axis Alignment
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Solution Overview
Problem
Existing pressure sensors with monocrystalline membrane and substrate connections experience directional-dependent crystal property jumps due to poor lateral orientation of mounting surfaces, leading to defects and inhomogeneous deflections, affecting long-term stability and measurement accuracy.
Innovation Solution
A pressure sensor design where the edge region of the monocrystalline membrane body has a greater material thickness than the measuring membrane, with mounting surfaces oriented parallel to each other's principal crystal axes, using eutectic or fusion bonding for connection, ensuring precise alignment and orientation of the membrane and substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mounting surfaces are connected with normal given by the same principal crystal axis, then connection is achieved, but lateral orientation is poor causing jumps in crystal properties
Solution Approach 1:
The patent introduces asymmetric orientation relationships between the membrane body and substrate. Specifically, while the surface normals are aligned along the same principal crystal axis (e.g., <100>), the lateral orientations are deliberately set to different principal crystal axes (e.g., one along <010> and the other along <0-10>). This asymmetric configuration eliminates poor lateral orientation while maintaining connection reliability through the preserved normal alignment.
Solution Approach 2:
The patent changes the orientation parameters of the mounting surfaces. By specifying that surface normals are given by the same principal crystal axis while lateral orientations follow different principal crystal axes, the patent transforms the orientation parameters to achieve both reliable connection and precise lateral alignment, eliminating the jumps in crystal properties.
2Strength
If eutectic bond with gold intermediate layer is used, then substrate and membrane body are joined, but reactions occur due to anisotropy of material parameters
Solution Approach 1:
The patent changes the geometric parameters of the mounting surfaces by optimizing their lateral orientations relative to the principal crystal axes. This parameter optimization reduces the anisotropic effects during bonding, minimizing reactions between substrate and membrane body while maintaining strong eutectic bonds with gold intermediate layer.
Solution Approach 2:
The patent applies different orientation configurations to different regions of the mounting surfaces. By carefully selecting the lateral orientations of specific surface areas relative to the principal crystal axes, the patent locally optimizes the bonding conditions to reduce anisotropic reactions while maintaining overall bond strength.
3Strength
If fusion bonding is used for connection, then joining is achieved, but anisotropic material properties lead to inhomogeneous deflections
Solution Approach 1:
The patent optimizes the orientation parameters of the mounting surfaces to be parallel to principal crystal axes. This parameter optimization ensures that during fusion bonding, the anisotropic material properties do not cause inhomogeneous deflections, as the symmetric orientation relative to crystal axes compensates for the anisotropy.
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 design significantly reduces defects and anisotropic material property issues, enhancing long-term stability and measurement accuracy by ensuring homogeneous deflections and improved material bonding.
Implementation Method 1
The substrate and the membrane body are joined to one another by a eutectic bond, which includes an intermediate layer of gold, which is required for forming the eutectic.
Implementation Method 2
Alternatively, a connection by what is called fusion bonding is possible for this.
Data Source
AI summary
A pressure sensor, comprising: a monocrystalline membrane body, which includes a measuring membrane and an edge region surrounding the measuring membrane. The edge region has a greater material thickness than the measuring membrane and the edge region has a first mounting surface, whose surface normal is given by a first principal crystal axis. A monocrystalline substrate, which, with respect to crystal structure, comprises the same semiconductor material as the membrane body, the substrate has a second mounting surface, whose surface normal extends parallel to the first principal crystal axis. The membrane body is tightly connected to the substrate by joining the first mounting surface to the second mounting surface. The orientations of other principal crystal axes of the membrane body and the substrate are, in each case, oriented parallel relative to one another.