IC Pressure Sensor Shielding via Grounded Membrane
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Solution Overview
Problem
Integrated circuits (ICs) with pressure sensors face challenges in miniaturization, including accuracy issues due to external electric fields affecting the sensor and the need for additional shielding, which complicates the IC design.
Innovation Solution
A pressure sensor design on a semiconductor substrate with a pair of electrodes and a flexible membrane that interferes with the fringe field, where the membrane is grounded to shield the electrodes from external fields, and an interconnect layer is used to improve measurement accuracy, allowing for integration in the IC manufacturing process without compromising other circuit elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a diaphragm electrode is used as one of the capacitor plates in the pressure sensor, then the sensor can be easily integrated in an IC design, but the diaphragm electrode deforms under the electric potential, reducing measurement accuracy and requiring additional shielding
Solution Approach 1:
The pressure sensor is divided into two separate functional components: a fixed capacitor electrode integrated on the IC substrate and a separate flexible diaphragm with aperture that does not serve as an electrode. This segmentation allows the capacitor structure to remain stable and integrated while the diaphragm responds purely to pressure changes without electrostatic deformation
Solution Approach 2:
A fixed capacitor electrode is introduced as an intermediary element between the pressure application point and the measurement circuit. This electrode remains stationary and does not deform, providing a stable reference for capacitance measurements while the diaphragm moves independently in response to pressure changes
2Measurement precision
If additional shielding is added to protect the electrode from external electric fields, then the sensor becomes more accurate, but the IC design complexity increases
Solution Approach 1:
The problematic diaphragm electrode is extracted from the capacitor structure, leaving only a fixed capacitor electrode on the IC substrate. This eliminates the need for shielding the moving diaphragm electrode from external fields, as the fixed electrode can be naturally shielded by the IC substrate structure without adding complexity
Solution Approach 2:
The capacitor electrode is merged with the existing IC substrate structure, utilizing the substrate as both the mechanical support and the electrical reference. This integration eliminates the need for separate shielding structures, as the substrate itself provides the necessary electrical isolation and mechanical support
3Volume of moving object
If the sensor is miniaturized for IC integration, then the IC scale is achieved, but accuracy issues arise due to external electric fields and miniaturization effects
Solution Approach 1:
The aperture region of the diaphragm is given special structural quality - it is thinned or perforated locally to enhance pressure sensitivity in that specific region, while the rest of the diaphragm maintains sufficient strength and stability. This local modification allows miniaturization without sacrificing accuracy
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 enhances the accuracy and robustness of the pressure sensor by shielding it from external influences and enabling the use of materials that would otherwise be unsuitable for high-temperature processing steps, while maintaining the sensitivity and reliability of the sensor.
Implementation Method 1
a flexible membrane spatially separated from said electrodes such that said membrane interferes with a fringe field between said electrodes
Implementation Method 2
the membrane is grounded to shield the electrodes from external fields
Implementation Method 3
Under the exertion of a pressure P on the diaphragm electrode 30, this electrode deforms towards the first electrode 20, thus causing a change in the capacitance C
Data Source
AI summary
Disclosed is an integrated circuit, comprising a semiconductor substrate carrying a plurality of circuit elements; and a pressure sensor including a cavity on said semiconductor substrate, said cavity comprising a pair of electrodes laterally separated from each other; and a flexible membrane over and spatially separated from said electrodes such that said membrane interferes with a fringe field between said electrodes, said membrane comprising at least one aperture. A method of manufacturing such an IC is also disclosed.