Stress Sensing Devices Using Vertical Resistor Configuration
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Solution Overview
Problem
Mechanical stress-induced drift in micro-electronic devices, such as Hall sensors and band-gap regulated reference voltages, is challenging to mitigate due to differences in temperature coefficients between vertical and lateral n-type resistors, which affect the accuracy of stress sensing.
Innovation Solution
A stress sensing device with a vertical resistor configuration, featuring multiple contacts and operating modes, allows for the measurement of mechanical stress by comparing resistance values across different modes, with a focus on vertical current flow to minimize temperature coefficient variations and enhance piezo-coefficient accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lateral p-type and lateral n-type resistors are used for stress sensing, then stress measurement can be achieved, but temperature coefficient mismatch between p- and n-type resistances degrades measurement precision
Solution Approach 1:
The patent uses two lateral n-type resistors instead of p-type and n-type resistors. Both resistors have identical doping types (n-type), ensuring matching temperature coefficients. The resistors are formed in the same n-well region, further ensuring homogeneous material properties and eliminating temperature drift differences between the two resistors.
2Reliability
If vertical and lateral n-type resistors are used for stress sensing, then temperature coefficient matching improves, but notable difference in temperature coefficients between vertical and lateral configurations still exists
Solution Approach 1:
The patent employs two lateral n-type resistors with identical orientation and configuration. Both resistors are formed in the same n-well region and have the same lateral geometry, ensuring completely homogeneous temperature coefficients. This eliminates the temperature coefficient mismatch problem that exists between vertical and lateral resistor configurations.
3Ease of manufacture
If different n-wells are used for lateral and vertical resistors, then device fabrication is enabled, but temperature coefficient dependency on doping level causes mismatch
Solution Approach 1:
The patent merges both resistors into a single shared n-well region. Instead of using separate n-wells for the two resistors, both lateral n-type resistors are formed in the same n-well, ensuring they experience identical doping levels and electrical characteristics. This eliminates temperature coefficient mismatch while maintaining CMOS fabrication compatibility.
4Measurement precision
If stress sensing is implemented using conventional resistor comparisons, then stress detection is achieved, but technology spread between different doping levels reduces measurement reliability
Solution Approach 1:
The patent uses two lateral n-type resistors formed in the same n-well region with identical doping levels and geometric configurations. This homogeneous design ensures that both resistors respond identically to process variations and technology spread, eliminating mismatch errors and improving measurement reliability across different manufacturing batches and technology nodes.
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 senses mechanical stress by providing a unique measure of stress through resistance comparisons across operating modes, reducing temperature-related errors and improving the accuracy of stress detection in micro-electronic devices.
Implementation Method 1
the stress sensing device is configured to sense a mechanical stress from vertical components in the active semiconductor layer of currents applied to at least one of the plurality of contacts
Data Source
AI summary
Embodiments relate to stress sensors and methods of sensing stress. In an embodiment, a stress sensor comprises a vertical resistor. The vertical resistor can comprise, for example, an n-type resistor and can have various operating modes. The various operating modes can depend on a coupling configuration of terminals of the resistor and can provide varying piezo-coefficients with very similar temperature coefficients of resistances. Comparisons of resistances and piezo-coefficients in differing operating modes can provide a measure of mechanical stresses acting on the device.