Capacitive MEMS Structure Without Via Electrodes or Side Etching
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Solution Overview
Problem
Existing MEMS devices face challenges in size reduction due to the need for via electrodes and side etching to ensure movable electrode ranges, which complicates miniaturization.
Innovation Solution
A MEMS device configuration using single-crystal silicon substrates with integrated electrostatic capacity portions between movable portions and covers, eliminating the need for via electrodes and side etching by direct bonding, allowing for size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon oxide layer is laminated on a Si substrate at the electrostatic capacity portion, then electrical connection is ensured, but via electrodes are required which increase device size
Solution Approach 1:
The patent removes the silicon oxide layer from the electrostatic capacity portion, extracting the problematic element that required via electrodes. By eliminating the oxide layer, the need for via electrodes is removed, enabling device size reduction while maintaining electrical connection through direct single-crystal silicon contact.
2Ease of operation
If side etching is executed for the silicon oxide layer, then movable range is ensured, but area of the silicon oxide layer must be sufficiently ensured which increases device size
Solution Approach 1:
The patent extracts the silicon oxide layer entirely from the electrostatic capacity portion, eliminating the need for side etching operations. The movable range is ensured through the spring portion design and single-crystal silicon structure without requiring additional area for oxide layer processing.
3Reliability
If via electrodes are disposed to electrically connect the Si substrate to a Si film, then electrical connection is achieved, but disposing space is required which prevents size reduction
Solution Approach 1:
The patent removes both the silicon oxide layer and the via electrodes, extracting the complex multi-layer structure. Electrical connection is achieved through direct contact between single-crystal silicon substrates, eliminating the need for via electrodes and reducing structural complexity.
Solution Approach 2:
The patent merges the electrostatic capacity portion directly with the single-crystal silicon substrate without intermediate oxide layers or via electrodes. This integration combines the substrate and electrostatic capacity functions into a unified structure, reducing complexity and enabling size reduction.
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
Enables size reduction and improved detection accuracy by eliminating the need for via electrodes and side etching, facilitating precise electrostatic capacity changes based on movable portion distances.
Implementation Method 1
the single-crystal silicon of the second substrate is joined to the single-crystal silicon of the first substrate
Implementation Method 2
electrostatic capacity changes depending on a distance between the movable portion and the upper cover or the first substrate
Data Source
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AI summary
A MEMS device (1) includes a lower cover (10), an upper cover (30) that forms a space between the upper cover (30) and the lower cover (10), a first substrate (20A) that is disposed opposite to the lower cover (10) in the space formed between the upper cover (30) and the lower cover (10) and is composed of single-crystal silicon, a second substrate (20B) that is disposed opposite to the upper cover (30) in the space formed between the upper cover (30) and the lower cover (10) and is composed of single-crystal silicon. The second substrate (20B) includes a movable portion (24B). The single-crystal silicon of the second substrate (20B) is joined to the single-crystal silicon of the first substrate (20A). The MEMS device (1) includes also an electrostatic capacity portion that is made at least one of between the upper cover (30) and the second substrate (20B) or between the first substrate (20A) and the second substrate (20B) and is configured such that electrostatic capacity changes depending on the distance between the movable portion (24B) and the upper cover (30) or the first substrate (20A).