MEMS Sensor Movable Weight Mass via Embedded High-Density Plugs
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Solution Overview
Problem
Existing MEMS sensors face challenges in increasing the mass of the movable weight portion while maintaining sensitivity and reducing noise, particularly in achieving miniaturization and integration with CMOS integrated circuits.
Innovation Solution
A MEMS sensor design featuring a stacked structure with conductive layers, inter-layer insulating layers, and plugs of higher specific gravity, which are embedded through the insulating layer, enhancing mass and sensitivity by forming a columnar or prismatic shape, and utilizing a CMOS process for manufacturing, allowing for increased mass and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the movable weight portion is formed only of the wiring layer with all inter-layer insulating layers removed, then the structure is simplified, but the mass of the movable weight portion is reduced
Solution Approach 1:
The movable weight portion is formed as a composite structure comprising conductive layers, inter-layer insulating layers, and plugs with different specific gravities. The plugs (having larger specific gravity than the insulating film) are embedded in the inter-layer insulating layer to increase the overall mass of the movable weight portion while maintaining the multi-layer composite structure that balances electrical and mechanical functions
2Weight of moving object
If plugs with larger specific gravity than the insulating film are embedded in the inter-layer insulating layer, then the mass of the movable weight portion is increased, but the manufacturing process becomes more complex
Solution Approach 1:
The plugs are embedded in the inter-layer insulating layer during the wiring formation process, before the movable weight portion structure is finalized. This preliminary placement of high-specific-gravity plugs allows the mass enhancement to be achieved as part of the standard multi-layer wiring fabrication sequence, reducing the need for separate post-processing steps
3Volume of moving object
If the sensor chip and IC chip are integrated by wafer process, then the size and cost are reduced, but the mass of the movable weight portion is limited by the available wiring layers
Solution Approach 1:
The movable weight portion utilizes a composite structure combining conductive layers, inter-layer insulating layers, and high-specific-gravity plugs. This composite approach enables mass enhancement within the constrained space of the integrated sensor chip, achieving higher mass without increasing the overall device volume, thus maintaining miniaturization while improving sensitivity
Solution Approach 2:
The plugs with larger specific gravity are strategically embedded in specific regions of the inter-layer insulating layer within the movable weight portion. This localized placement of high-density material concentrates the mass increase in the critical sensing region, optimizing sensitivity enhancement within the limited space available in the integrated sensor structure
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 design effectively increases the mass of the movable weight portion, improves detection sensitivity, and reduces manufacturing costs by integrating the MEMS sensor with the CMOS integrated circuit on the same substrate, minimizing noise and enabling miniaturization.
Implementation Method 1
a plug that is filled into an embedding groove pattern formed to penetrate through the inter-layer insulating layer and has a larger specific gravity than the inter-layer insulating film
Implementation Method 2
an elastically deformable connecting portion that supports the movable weight portion by coupling to the supporting portion and varies the facing distance between the facing-electrode face and the movable-electrode face
Implementation Method 3
a MEMS sensor (for example, electrostatic capacitive acceleration sensor)
Data Source
AI summary
A MEMS sensor includes: a substrate; a fixed electrode portion formed in the substrate; a movable weight portion formed above the fixed electrode portion via a gap; a movable electrode portion formed in the movable weight portion and disposed so as to face the fixed electrode portion; a supporting portion; and a connecting portion that couples the supporting portion with the movable weight portion and is elastically deformable, wherein the movable weight portion is a stacked structure having conductive layers and an insulating layer, and plugs having a larger specific gravity than the insulating layer are embedded in the insulating layer.