Single Chip Inertial and Pressure Sensor Integration
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Solution Overview
Problem
Existing MEMS devices face challenges in fabricating out-of-plane electrodes due to packaging difficulties and require dedicated process flows for each sensor type, making it hard to combine multiple sensing devices on a single chip effectively.
Innovation Solution
A single chip combination inertial and pressure sensor device is fabricated using a unified process flow, where the pressure sensor is integrated within the membrane layer, and inertial sensors utilize insulating nitride plugs for differential sensing, allowing for reduced sensor area and shared design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If out-of-plane electrodes are used in MEMS devices, then transduction efficiency is improved, but packaging difficulty increases due to electrode damage during packaging processes
Solution Approach 1:
The patent transitions from in-plane electrode configuration to out-of-plane electrode configuration, changing the dimensional orientation of the electrodes. This allows the movable electrode to be positioned above the fixed electrode in the vertical dimension, achieving larger transduction area without increasing the planar footprint, thereby improving transduction efficiency while maintaining device compactness for packaging
2Manufacturing precision
If dedicated process flows are used for each sensor type, then manufacturing precision is maintained, but device complexity increases when combining multiple sensors on a single chip
Solution Approach 1:
The patent develops a unified process flow that can fabricate multiple types of MEMS sensors (accelerometers, gyroscopes, pressure sensors) on a single chip using the same manufacturing steps. The process uses universal layers (device layer, buried oxide layer, cap layer) and common fabrication techniques (etching, deposition, release) to create different sensor types, eliminating the need for separate dedicated process flows for each sensor type
3Productivity
If multiple sensors are fabricated on a single chip, then productivity is improved, but manufacturing precision deteriorates due to process integration challenges
Solution Approach 1:
The patent divides the chip into distinct functional regions with separate sensing structures (inertial sensors in device layer, pressure sensors utilizing membrane layers) that can be independently designed and optimized. Each sensor type has its own sensing elements and electrodes, allowing independent fabrication and testing while being produced on the same chip through the unified process flow
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 approach enables the creation of a single chip device with combined inertial and pressure sensors, achieving greater transduction efficiency and reduced footprint, while maintaining the design flexibility of current inertial sensors and allowing for reliable vacuum encapsulation.
Implementation Method 1
a movable sensing structure (350) positioned between the flexible membrane (162) and the substrate (106) and configured as an electrode in the pressure sensor
Implementation Method 2
a fixed electrode (120) formed in the substrate (106) and configured as an electrode in the inertial sensor
Data Source
AI summary
In accordance with one embodiment, a single chip combination inertial and pressure sensor device includes a substrate, an inertial sensor including a movable sensing structure movably supported above the substrate, and a first fixed electrode positioned adjacent to the movable sensing structure, and a pressure sensor including a gap formed in the sensor at a location directly above the movable sensing structure, and a flexible membrane formed in a cap layer of the device, the flexible membrane defining a boundary of the gap and configured to flex toward and away from the gap in response to a variation in pressure above the flexible membrane.