Semiconductor Pressure Sensor With Orthogonal Bridge Compensation
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Solution Overview
Problem
Conventional semiconductor pressure sensors are unable to effectively compensate for non-linear or localized stress and temperature gradients, leading to inaccurate output signals due to external influences such as stress sources and temperature gradients.
Innovation Solution
A semiconductor pressure sensor design featuring a Wheatstone bridge configuration with sensing and compensating resistor pairs, where the compensating pairs are located on or outside the membrane's zero stress zone, and the resistors are oriented orthogonally to minimize the impact of stress and temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezo resistors are placed on the membrane edge in a Wheatstone bridge configuration, then the sensor can detect differential pressure, but the sensor becomes sensitive to external stress and temperature gradients causing undesired signals
Solution Approach 1:
The sensor divides the piezo resistor configuration into two separate groups: a first group of piezo resistors placed on the membrane edge for pressure sensing, and a second group of piezo resistors placed on the substrate away from the membrane edge. This segmentation allows each group to experience different stress conditions, enabling compensation of external stress and temperature effects through differential measurement.
Solution Approach 2:
The second group of piezo resistors acts as an intermediary reference that experiences the same external stress and temperature gradients but not the pressure-induced membrane stress. By comparing the output of the first group (on membrane) with the second group (on substrate), the circuit can isolate and compensate for environmental effects, serving as a mediator between the sensing element and the measurement system.
2Measurement precision
If all piezo resistors are placed on the membrane edge to maximize pressure sensitivity, then pressure detection capability is improved, but compensation for non-linear stress gradients becomes ineffective
Solution Approach 1:
The invention applies different spatial qualities to different piezo resistor groups: the first group is located at the membrane edge where stress is concentrated and linearly distributed, while the second group is located on the substrate where stress is minimal or zero. This local quality differentiation enables the system to capture both pressure-induced stress and environmental stress separately, allowing effective compensation even under non-linear stress gradient conditions.
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 design significantly reduces or eliminates signal variations caused by stress and temperature gradients, ensuring accurate pressure measurement by maintaining a constant differential output.
Implementation Method 1
The piezo resistors are placed on the edge of a membrane in a transversal and longitudinal direction with respect to the membrane stress that is proportional to the applied pressure. When a differential pressure is applied to the membrane, the membrane will bend and will create a stress on the edges of the membrane. This stress will change the resistance of the piezo resistors
Data Source
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AI summary
A semiconductor pressure sensor for measuring an external pressure exerted on the sensor, comprising a membrane as part of a semiconductor substrate for being deformed due to the external pressure, a first group of neighboring resistors comprising a sensing resistor pair and a compensating resistor pair and a second group of neighboring resistors comprising a sensing resistor pair and a compensating resistor pair, wherein the sensing resistor pairs are located on or adjacent to the membrane edge and wherein the compensating resistor pairs are located at least partially outside the membrane or on a zero stress zone of the membrane, and wherein the resistors of each resistor pair are orthogonal, and wherein the resistors are connected in a Wheatstone bridge configuration.