Buried Electrode MEMS via Segmented Dielectric Stacks
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Solution Overview
Problem
Many capacitive MEMS devices face limitations in arbitrary placement of electrodes and out-of-plane configurations due to restrictive encapsulation methods, which hinder their operational performance and flexibility.
Innovation Solution
The method involves forming a MEMS device using a silicon on insulator (SOI) wafer with multiple electrodes and contacts, where each electrode is defined in specific layers and connected through dielectric layers, allowing for electrical communication and isolation, enabling flexible electrode configurations and enhanced device operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional encapsulation methods are used, then device structure is simplified, but electrode placement flexibility is limited
Solution Approach 1:
The encapsulation structure is divided into multiple dielectric layers (first dielectric layer, second dielectric layer, third dielectric layer) with each layer serving specific functions. The first dielectric layer provides electrical isolation, the second dielectric layer provides mechanical support and additional isolation, and the third dielectric layer provides final encapsulation. This segmentation allows electrodes to be placed at different depths and positions while maintaining electrical isolation and mechanical integrity, thereby achieving electrode placement flexibility without overwhelming complexity.
Solution Approach 2:
The patent transitions from planar electrode configuration to three-dimensional electrode placement by utilizing multiple vertical layers. Electrodes are positioned at different heights (first electrode in first layer, second electrode in second layer, third electrode in third layer), enabling out-of-plane electrode configurations that were not possible with conventional single-layer encapsulation. This dimensional expansion provides arbitrary placement capability while maintaining a systematic structure.
2Reliability
If multiple electrodes are added for enhanced performance, then device functionality is improved, but manufacturing complexity increases
Solution Approach 1:
Each dielectric layer serves multiple functions simultaneously. For example, the first dielectric layer provides both electrical isolation between electrodes and mechanical support. The second dielectric layer provides both additional electrical isolation and structural support for the third electrode. The third dielectric layer provides final encapsulation and protection. This multi-functionality reduces the need for separate components, thereby improving device performance without proportionally increasing manufacturing complexity.
Solution Approach 2:
The electrode structure is nested within the dielectric layers, with each electrode embedded in its respective layer. The first electrode is defined in the first dielectric layer, the second electrode in the second dielectric layer, and the third electrode in the third dielectric layer. This nesting approach allows multiple electrodes to coexist in a compact three-dimensional arrangement, enhancing device functionality while maintaining a systematic and manageable structure that does not excessively complicate manufacturing.
3Adaptability or versatility
If electrodes are placed in multiple layers, then arbitrary electrode placement is achieved, but process steps increase
Solution Approach 1:
The dielectric layers are formed in a predetermined sequence before electrode deposition. The first dielectric layer is formed to define the first electrode region, the second dielectric layer is formed to define the second electrode region, and the third dielectric layer is formed to define the third electrode region. This preliminary structuring of the dielectric layers establishes the framework for electrode placement, allowing subsequent electrode deposition processes to follow a systematic pattern that does not significantly increase manufacturing complexity despite the multi-layer configuration.
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 allows for arbitrary placement of electrodes, improving the operational flexibility and performance of capacitive MEMS devices by enabling closed-loop and differential sensing capabilities.
Implementation Method 1
forming a first contact above the second layer in electrical communication with the first electrode through the second layer and the first layer
Implementation Method 2
forming a second contact above the second layer in electrical communication with the second electrode through the second layer
Implementation Method 3
defining a third contact above the second layer in electrical communication with the third
Implementation Method 4
forming a first contact above the second layer in electrical communication with the first electrode through the second layer and the first layer
Data Source
AI summary
A system and method for forming a sensor device with a buried first electrode includes providing a first silicon portion with an electrode layer and a second silicon portion with a device layer. The first silicon portion and the second silicon portion are adjoined along a common oxide layer formed on the electrode layer of the first silicon portion and the device layer of the second silicon portion. The resulting multi-silicon stack includes a buried lower electrode that is further defined by a buried oxide layer, a highly-doped ion implanted region, or a combination thereof. The multi-silicon stack has a plurality of silicon layers and silicon dioxide layers with electrically isolated regions in each layer allowing for both the lower electrode and an upper electrode. The multi-silicon stack further includes a spacer that enables the lower electrode to be accessible from a topside of the sensor device.