Semiconductor Pressure Sensor Piezo-Resistive Stress Compensation
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Solution Overview
Problem
Semiconductor pressure sensors face inaccuracies due to temperature fluctuations, residual package-stress, and non-uniform electric fields, which affect their accuracy, linearity, and sensitivity.
Innovation Solution
A semiconductor pressure sensor design featuring a membrane with resistor pairs oriented in perpendicular directions, connected to current sources to produce differential voltage signals, minimizing temperature influence and enhancing sensitivity and linearity, while separate resistor pairs outside the membrane measure packaging stress to compensate for uniform stress effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional pressure sensor with piezo-resistive strips is used, then the sensor can detect pressure changes, but the accuracy deteriorates under temperature fluctuations and residual package stress
Solution Approach 1:
The sensor measures different physical quantities by separating measurement locations: resistor pairs on the membrane measure pressure, while resistor pairs outside the membrane measure only package stress and temperature effects. This segmentation allows independent measurement and subsequent compensation of harmful factors.
Solution Approach 2:
Resistor pairs positioned outside the membrane serve as intermediaries to measure environmental effects (temperature and package stress) separately. These measurements are then used to compensate the main pressure measurement, acting as a mediator to eliminate harmful influences.
2Measurement precision
If resistor pairs are positioned on the membrane for pressure sensing, then sensitivity is improved, but the sensor becomes more sensitive to temperature gradients and non-uniform stress
Solution Approach 1:
The measurement system is divided into two functional segments: membrane-mounted resistors for pressure sensing and external resistors for environmental effect sensing. This allows the pressure-sensitive components to maintain high sensitivity while separate components compensate for temperature and stress variations.
Solution Approach 2:
The sensor utilizes changes in electrical resistance parameters of piezo-resistive strips in response to mechanical stress and temperature. By measuring resistance changes in both membrane and external resistors, the system distinguishes between pressure-induced changes and environmental changes.
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 achieves improved accuracy, linearity, and sensitivity by isolating temperature and stress effects, providing a more reliable pressure measurement even under non-uniform conditions.
Implementation Method 1
the first resistor comprising one or more first elongated piezo-resistive strips arranged in a first direction for measuring deformation of the membrane due to the external pressure to be measured, the second resistor comprising one or more second elongated piezo-resistive strips arranged in a second direction for measuring deformation of the membrane
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A semiconductor pressure sensor for measuring an external pressure exerted on the sensor, comprises: a membrane; a first resistor (R1) connected between a first bias node (A) and a first output node (D); a second resistor (R2) connected between said first bias node (A) and a second output node (B); a first and second current source (CS1) connected to the first resp. second output node (D,B) for generating a differential voltage signal (ΔVout) indicative of the external pressure to be measured. The resistors (R1, R2) comprise piezo-resistive strips arranged in particular crystallographic directions. The circuit may have a third and four resistor pair (P3, P4) for compensating package stress. The Piezo-resistive strips may be formed as p-doped regions within an n-well, the biasing node (A) being electrically connected to the n-well.