Integrated Diode Temperature Sensor for Piezoresistive Pressure Transducer
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Solution Overview
Problem
Piezoresistive pressure sensors experience high thermal drift due to temperature variations, leading to signal instability, especially in sensitive applications, and existing compensation methods increase sensor size and require additional pads, complicating manufacturing and layout.
Innovation Solution
A transducer with an integrated temperature sensor using a semiconductor material junction diode, where a current is supplied to detect a voltage value across the diode, correlating it to the temperature, allowing for effective thermal compensation without increasing sensor size or requiring additional pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate temperature sensor is added to compensate for thermal drift, then temperature compensation accuracy is improved, but sensor area and device complexity increase
Solution Approach 1:
The patent merges the temperature sensing function with the existing piezoresistive sensing structure by utilizing the same semiconductor membrane and diffused resistors. The temperature compensation is achieved by configuring resistors in a Wheatstone bridge arrangement where temperature-induced resistance changes in all resistors are equal and thus cancel out, providing temperature compensation without requiring separate temperature sensor elements or additional area.
Solution Approach 2:
The piezoresistive membrane structure serves dual functions: it acts as both the pressure sensing element and the temperature compensation reference. The same diffused resistors on the membrane are used for both pressure measurement and temperature compensation, eliminating the need for dedicated temperature sensor components and reducing overall device complexity.
2Reliability
If additional temperature sensing circuits are integrated, then thermal drift compensation is improved, but manufacturing complexity and pad requirements increase
Solution Approach 1:
The temperature compensation function is merged into the existing piezoresistive sensor fabrication process. The same diffusion steps used to create the piezoresistors for pressure sensing are used to create the temperature compensation resistors, eliminating additional manufacturing steps and reducing process complexity.
Solution Approach 2:
The Wheatstone bridge circuit configuration serves dual purposes: it provides the pressure measurement output while simultaneously providing temperature compensation. The bridge arrangement ensures that temperature-induced resistance changes affect all arms equally, causing the temperature effects to cancel out in the differential output, thus achieving reliable thermal drift compensation without additional circuits.
3Measurement precision
If separate temperature sensor elements are used, then temperature measurement accuracy is improved, but warm-up drift time increases
Solution Approach 1:
The temperature sensing function is combined with the pressure sensing membrane, ensuring both functions share the same thermal environment and reach thermal equilibrium simultaneously. This eliminates warm-up drift time issues that occur when separate temperature sensors are placed at different locations, as the integrated structure ensures uniform temperature distribution across all sensing elements from the start.
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 solution reduces warm-up drift times, saves area by using integrated diodes, and eliminates the need for dedicated pads, maintaining the sensor's layout and functionality while providing accurate temperature compensation.
Implementation Method 1
A transducer with an integrated temperature sensor using a semiconductor material junction diode, where a current is supplied to detect a voltage value across the diode, correlating it to the temperature
Implementation Method 2
the piezoresistive effect, whereby the deflection of a silicon membrane caused by the pressure unbalances a Wheatstone bridge provided with resistances diffused in the membrane
Data Source
AI summary
A pressure sensor includes a body made of semiconductor material having a first type of conductivity and a pressure-sensitive structure having the first type of conductivity defining a suspended membrane. One or more piezoresistive elements having a second type of conductivity (P) are formed in the suspended membrane. The piezoresistive elements form, with the pressure-sensitive structure, respective junction diodes. A temperature sensing method includes: generating a first current between conduction terminals common to the junction diodes; detecting a first voltage value between the common conduction terminals when the first current is supplied; and correlating the detected first voltage value to a value of temperature of the diodes. The temperature value thus calculated can be used for correcting the voltage signal generated at output by the pressure sensor when the latter is operated for sensing an applied outside pressure which deforms the suspended membrane.