3D Deformable Stress Sensor Cavity Design
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Solution Overview
Problem
Conventional stress-sensitive pressure sensing devices are limited by their planar design, which restricts the number and size of resistors, makes them susceptible to packaging stresses, and faces manufacturing challenges such as stiction and limited z-axis height of sacrificial films.
Innovation Solution
The development of a three-dimensional stress-sensitive device with a deformable material extending along a substrate surface and into a cavity, featuring multiple edges and surfaces that deform under pressure, allowing for increased strain and signal output without occupying additional substrate space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If planar piezoresistive devices are used, then manufacturing is simpler, but signal strength is limited and substrate area is consumed
Solution Approach 1:
The patent transitions from planar (2D) piezoresistive structures to three-dimensional (3D) deformable structures that extend vertically into cavities etched in the substrate. This dimensional change allows the deformable material to utilize the z-axis height, creating multiple deformation surfaces and edges that generate higher strain and signal output without requiring additional substrate surface area.
2Measurement precision
If planar devices with single edge deformation are used, then device structure is simpler, but sensitivity is limited
Solution Approach 1:
The invention creates 3D deformable structures with multiple edges and surfaces that can deform under applied pressure. These structures extend vertically into substrate cavities, providing multiple deformation zones along the height of the structure, which increases the number of piezoresistive elements experiencing stress and thereby enhances overall sensitivity.
Solution Approach 2:
The deformable material is structured with multiple edges and surfaces distributed throughout the 3D volume, effectively segmenting the deformation response across multiple locations. Each edge and surface contributes to the overall strain measurement, allowing the device to capture stress from multiple perspectives simultaneously.
3Reliability
If packaging stress mitigation techniques are added, then reliability improves, but device complexity and cost increase
Solution Approach 1:
By extending the deformable structures vertically into substrate cavities, the patent creates physical separation between the active sensing elements and the substrate surface. This 3D configuration reduces the transmission of packaging stresses from the substrate to the deformable material, as the cavity acts as a stress-isolating space, thereby improving reliability without requiring additional packaging mitigation techniques.
4Ease of operation
If devices stand proud above substrate surface, then accessibility is improved, but susceptibility to damage increases
Solution Approach 1:
The patent inverts the conventional approach by extending deformable structures downward into substrate cavities rather than upward above the substrate surface. This downward extension protects the fragile deformable material by embedding it within the substrate volume, shielding it from mechanical damage while maintaining electrical and functional accessibility through the substrate.
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 enhances signal strength for reduced substrate area, reduces susceptibility to external stresses, and simplifies packaging, enabling the production of more devices on a single substrate while minimizing manufacturing complexities.
Implementation Method 1
Conventional stress-sensitive pressure sensing devices, such as piezoresistive pressure sensors
Implementation Method 2
a three-dimensional deformable material extending along the first surface and into the cavity. The three-dimensional deformable material has an electrical characteristic responsive to deformation
Data Source
AI summary
A stress-sensitive device includes a substrate having a first surface with a cavity defined therein and a three-dimensional deformable material extending along the first surface and into the cavity. The three-dimensional deformable material has an electrical characteristic responsive to deformation. A method of forming a three-dimensional stress-sensitive device includes providing a substrate having a first surface and a second surface opposite the first surface, forming a cavity in the substrate, wherein the cavity is open to the first surface, depositing a sacrificial layer in the cavity, depositing a deformable material on the sacrificial layer, and removing at least a portion of the sacrificial layer to form an interstitial space between the deformable material and the substrate in the cavity.