Multi-Axial Force Sensor With Orthogonal Trenches
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Solution Overview
Problem
Current semiconductor force sensors are limited in measuring high pressures and multi-axial loads, requiring complex and costly packages, and lack sensitivity and resolution for high full-scale ranges, especially when designed to measure normal forces rather than combinations of normal and shear forces.
Innovation Solution
A microelectromechanical transducer with a semiconductor-based multi-axial force sensor design that incorporates a silicon sensor body with orthogonal trenches and piezoresistive groups, allowing for the measurement of both normal and shear forces through a Wheatstone bridge configuration, enabling the detection of planar stress distributions and providing improved mechanical coupling and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If semiconductor force sensors are used for high-pressure applications, then measurement capability is improved, but device complexity and packaging requirements increase
Solution Approach 1:
The patent transitions from traditional planar membrane sensors to a three-dimensional sensor body with vertically oriented piezoresistive elements and trenches. This dimensional change allows the sensor to measure high forces directly through the sensor body itself, eliminating the need for complex external packaging structures while maintaining measurement capability.
Solution Approach 2:
The sensor body is designed to perform multiple functions: it serves as both the structural element that withstands high pressures and the sensing element that measures forces. The integration of piezoresistive elements directly into the sensor body allows it to function as both load-bearing structure and measurement transducer, reducing packaging complexity.
2Device complexity
If traditional semiconductor sensors measure only normal force, then device simplicity is maintained, but measurement versatility deteriorates
Solution Approach 1:
The sensor body is segmented into multiple functional regions with trenches creating distinct sensing zones. Different piezoresistive elements are positioned to respond to different force components (normal force, shear forces in x and y directions), allowing multi-axial measurement while maintaining a relatively simple monolithic sensor body structure.
Solution Approach 2:
The patent uses asymmetric trench configurations and strategically positioned piezoresistive elements to differentiate between various force components. The trenches are oriented in specific directions and piezoresistors are placed at locations that maximize sensitivity to particular force vectors, enabling versatile multi-axial measurement capability.
3Adaptability or versatility
If metallic load cells are used for multi-axial force measurement, then measurement versatility is improved, but sensitivity and resolution deteriorate
Solution Approach 1:
The patent replaces traditional metallic mechanical strain gauge systems with semiconductor piezoresistive elements integrated directly into a silicon sensor body. This substitution leverages the higher piezoresistive coefficient of silicon to achieve superior sensitivity and resolution while maintaining multi-axial measurement capability through strategic element placement and trench configurations.
4Reliability
If ceramic load cells are used for multi-axial force sensing, then durability is improved, but manufacturing flexibility and miniaturization deteriorate
Solution Approach 1:
The patent employs standard semiconductor manufacturing parameters and processes (photolithography, doping, etching) to create the sensor structure. By changing from ceramic fabrication to semiconductor processing, the invention achieves better miniaturization and design flexibility while maintaining durability through the inherent robustness of the silicon sensor body and integrated structure.
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 solution enables accurate measurement of multi-axial forces, including non-homogeneous loads, with enhanced sensitivity and reduced complexity and cost, overcoming the limitations of existing semiconductor sensors by effectively detecting force components along multiple axes.
Implementation Method 1
When subjected to a force, the membrane undergoes deformation, causing a variation of resistance of the piezoresistive elements
Data Source
AI summary
A microelectromechanical transducer includes a semiconductor body having first and second surfaces opposite to one another. A plurality of trenches extend in the semiconductor body from the first surface towards the second surface, including a first pair of trenches having a respective main direction of extension along a first axis, and a second pair of trenches having a respective main direction of extension along a second axis orthogonal to the first axis. A first piezoresistive sensor and a second piezoresistive sensor extend at the first surface of the semiconductor body respectively arranged between the first and second pair of trenches. The first piezoresistive sensor, the second piezoresistive sensor and the plurality of trenches form an active region. A first structural body is mechanically coupled to the first surface of the semiconductor body to form a first sealed cavity which encloses the active region.