Semiconductor Strain Gauge Insulation Layer Blocks Ion Migration
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Solution Overview
Problem
Microfused silicon strain gauge pressure sensors face challenges in maintaining accurate pressure measurements due to nonlinearity and signal drift caused by ionic migration and temperature changes, especially when continuously powered over extended periods.
Innovation Solution
A highly doped semiconductor strain gauge with a five pad single full Wheatstone bridge configuration and an insulation layer on the sidewall, which includes silicon nitride, is used to reduce nonlinearity and signal drift by blocking mobile ion migration, and is glass-bonded to a steel diaphragm for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a conventional silicon strain gauge is used, then the sensor can operate continuously, but signal drift occurs due to ionic migration
Solution Approach 1:
An insulation layer is introduced as an intermediary between the highly doped semiconductor strain gauge and the glass bond. This insulation layer acts as a mediator that blocks ionic migration from the glass to the strain gauge, preventing signal drift while allowing the sensor to operate continuously without degradation
2Manufacturing precision
If a highly doped semiconductor strain gauge is used, then manufacturing precision is improved, but ionic migration causes signal drift
Solution Approach 1:
The insulation layer serves as a protective intermediary that shields the highly doped semiconductor strain gauge from ionic migration. This allows the benefits of high doping (improved manufacturing precision and gauge factor consistency) to be maintained while the insulation layer prevents the harmful ionic migration that would otherwise cause signal drift
3Device complexity
If glass bonding is used to attach the strain gauge, then the sensor structure is simplified, but ionic migration occurs from the glass
Solution Approach 1:
The bonding structure is segmented into three distinct layers: the glass bond layer, an intermediate insulation layer, and the semiconductor strain gauge. This segmentation separates the glass from direct contact with the strain gauge, allowing the glass to provide structural bonding while the insulation layer blocks ionic migration, thus resolving the contradiction between structural simplicity and preventing harmful ionic migration
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 effectively reduces pressure nonlinearity and sensor signal drift, providing a more accurate and stable pressure measurement by using a five pad silicon gauge configuration and an insulation layer to prevent ionic migration, thus enhancing the reliability of the pressure sensor.
Implementation Method 1
an insulation layer on a sidewall... blocking mobile ion migration
Implementation Method 2
four piezoresistive resistors... directly proportional to the applied pressure on the steel diaphragm
Implementation Method 3
a five pad single full Wheatstone bridge... provides a linear voltage output which is directly proportional to the applied pressure
Data Source
AI summary
Methods and apparatus for a semiconductor strain gauge pressure sensor. An apparatus includes a sense element configured to be exposed to a pressure environment, the sense element including at least one highly doped semiconductor strain gauge, the highly doped semiconductor strain gauge including a five pad single full Wheatstone bridge, an electronics package disposed on a carrier and electrically coupled to the sense element, the carrier disposed on a port that comprises the sense element, a housing disposed about the sense element and electronics package, and a connector joined to the housing and electrically connected to the electronics package, the connector including an external interface.