MEMS Piezoresistive Acceleration Sensor Support Beam Wiring
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Solution Overview
Problem
Existing acceleration sensors face challenges in reliably screening for characteristic failures, particularly due to breakage of the support beam during manufacturing, which complicates the detection of variations in vibration characteristics and output from the piezoresistive element.
Innovation Solution
The acceleration sensor design includes a support beam with a wiring portion that allows for easier screening of characteristics by passing through the support beam, using injection wiring with impurities in the silicon substrate to minimize stress and detect breakage, and an enlarged wiring width to reduce resistance and detect breakage across the support beam's width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistance wiring for failure detection is provided around the periphery of the piezoresistive element, then detection of detection beam breakage is improved, but the screening operation becomes troublesome and unreliable for support beam breakage
Solution Approach 1:
The wiring portion is extracted from its conventional position around the piezoresistive element and relocated to pass through the support beam. This extraction allows the wiring to directly detect support beam breakage while maintaining the screening function, resolving the unreliability issue without complicating the operation.
Solution Approach 2:
The wiring portion acts as an intermediary element that bridges the detection function with the support beam structure. By passing through the support beam, it directly senses breakage events, serving as a reliable mediator between the support beam integrity and the screening operation.
2Use of energy by moving object
If a metal wiring is used for the wiring portion, then electrical conductivity is improved, but film stress acts on the support beam causing temperature-dependent characteristic variation
Solution Approach 1:
The material parameter of the wiring portion is changed from metal to injection wiring (semiconductor material). This parameter change eliminates the film stress issue that caused temperature-dependent characteristic variation, while the injection wiring maintains sufficient electrical conductivity for the detection function.
3Ease of manufacture
If the wiring portion has standard wiring width, then manufacturing simplicity is maintained, but wiring resistance is high and breakage detection across the support beam width is limited
Solution Approach 1:
The wiring portion is designed with non-uniform width, featuring an enlarged wiring width portion at the center of the support beam. This local quality enhancement reduces wiring resistance in the critical detection region and enables breakage detection across the entire support beam width, while keeping other regions with standard width for manufacturing simplicity.
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 configuration simplifies the screening process by eliminating the need to rely on piezoresistive element output variations and ensures more reliable detection of characteristic failures, reducing unnecessary stress and temperature-induced variations in sensor characteristics.
Implementation Method 1
a piezoresistive element is provided on the detection beam
Implementation Method 2
the wiring portion includes an injection wiring including impurities in the silicon substrate
Data Source
AI summary
An acceleration sensor includes a fixing portion, a weight portion, a detection beam, support beams, and a metal wiring. The weight portion is supported on the fixing portion so as to be freely displaced. The detection beam is connected to the fixing portion and the weight portion and piezoresistive elements are provided on the detection beam. The support beams are provided separately from the detection beam and are connected to the fixing portion and the weight portion. Both ends of the metal wiring are extended to the fixing portion and the metal wiring is wired so as to pass through the support beams.