MEMS Pressure Sensor Monolithic Integration via Conductive Plugs
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Solution Overview
Problem
Existing methods for fabricating MEMS capacitive type pressure sensors face challenges in achieving monolithic integration of pressure sensors and integrated circuits, leading to increased size, complexity, and cost due to separate fabrication processes and material limitations.
Innovation Solution
A method involving the bonding of a first substrate with a conductive layer and a second substrate containing a pressure-sensing electrode, forming a cavity, and creating a conductive plug to electrically connect the pressure-sensing electrode, allowing for independent fabrication processes and flexible material selection, thereby simplifying integration and reducing size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate fabrication processes are used for pressure sensor and integrated circuit, then material selection flexibility is improved, but device size and fabrication complexity increase
Solution Approach 1:
The patent divides the device into two separate substrates: a first substrate for the integrated circuit and a second substrate for the pressure sensor. This segmentation allows independent fabrication processes and material selection for each substrate, resolving the contradiction between material flexibility and fabrication complexity.
Solution Approach 2:
The patent merges the two separately fabricated substrates into a single integrated device through bonding. The first substrate containing the integrated circuit and the second substrate containing the pressure sensor are bonded together, achieving monolithic integration while maintaining the benefits of separate fabrication processes.
2Reliability
If pressure sensor is fabricated before integrated circuit, then pressure sensor performance is improved, but integrated circuit fabrication becomes difficult
Solution Approach 1:
The patent performs preliminary fabrication of the pressure sensor on the second substrate before bonding to the first substrate. This allows optimization of pressure sensor performance through specialized processes while keeping the integrated circuit fabrication on the first substrate independent and unaffected.
3Ease of manufacture
If integrated circuit is fabricated before pressure sensor, then integrated circuit functionality is ensured, but pressure sensor material choices are limited
Solution Approach 1:
By segmenting the device into separate substrates, the patent enables the second substrate to use materials optimized for pressure sensing (such as piezoresistive materials) without constraining the first substrate's integrated circuit fabrication processes.
4Reliability
If additional conductive layers are added for integration, then electrical connection is achieved, but device size and fabrication cost increase
Solution Approach 1:
The patent extracts the electrical connection function to through-substrate conductive plugs that pass directly through the substrates, eliminating the need for additional intermediate conductive layers. This reduces device complexity and size while maintaining reliable electrical connections between the pressure sensor and integrated circuit.
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 results in a more reliable, stable, and cost-effective MEMS pressure sensor with improved durability and sensitivity by eliminating the need for additional conductive layers and allowing for flexible material selection, while reducing the size and enhancing integration compatibility with integrated circuit fabrication processes.
Implementation Method 1
forming a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer, where the first conductive plug is used to electrically connect the conductive layer to the pressure-sensing electrode
Implementation Method 2
forming a cavity between the first substrate and the pressure sensing region of the second substrate
Data Source
AI summary
Provided are a MEMS pressure sensor and a method for forming the same. The method includes: preparing a first substrate including a first surface and a second surface opposite to each other; preparing a second substrate including a third surface and a fourth surface opposite to each other; bonding the first surface and the third surface with each other and forming a cavity between the first substrate and the pressure sensing region of the second substrate; thinning the second substrate from the fourth surface by partially removing the second base, to form a fifth surface opposite to the third surface; and forming a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer.