Dual MEMS Structure With Dielectric Isolation for Stable Capacitance
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Solution Overview
Problem
Existing MEMS devices face issues such as capacitance shifts due to unwanted electrode gaps, damage from plasma etching, and pattern sticking during manufacturing, particularly when forming large structures like proof masses over substrates with CMOS circuits.
Innovation Solution
The dual MEMS structure design incorporates dielectric layers between MEMS structures and a cover layer, using chemical dry etching to form patterns, and includes stopper patterns to prevent sticking, thereby isolating MEMS structures from substrate deformation and plasma damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma dry etching is used to form MEMS patterns, then manufacturing speed is improved, but plasma damage occurs to the patterns and substrate
Solution Approach 1:
A sacrificial dielectric layer is introduced as an intermediary between the MEMS patterns and the plasma environment during dry etching. This layer absorbs the plasma damage while protecting the underlying MEMS structures, allowing high-speed plasma etching to proceed without direct harm to the patterns and substrate.
Solution Approach 2:
The harmful plasma damage that would normally affect MEMS patterns is redirected to benefit the sacrificial dielectric layer, which is designed to be consumed by the plasma. This converts the harmful plasma into a useful tool for selectively removing the sacrificial layer while preserving the MEMS structures.
2Adaptability or versatility
If large proof mass structures are formed over CMOS substrates, then device functionality is improved, but pattern sticking occurs during manufacturing
Solution Approach 1:
The manufacturing process is segmented into distinct stages with different dielectric layers serving specific functions. The first dielectric layer enables formation of large proof mass structures, while the second dielectric layer provides release functionality. This segmentation allows each layer to be optimized for its specific purpose, preventing pattern sticking.
Solution Approach 2:
The sacrificial dielectric layer acts as an intermediary that facilitates the formation of large proof mass structures during manufacturing. It provides a temporary support and release mechanism that prevents pattern sticking, and is subsequently removed to leave the desired large-scale MEMS structure.
3Device complexity
If MEMS structures are directly connected to substrate, then electrical connection is simplified, but capacitance shifts occur due to unwanted electrode gaps
Solution Approach 1:
Dielectric layers are introduced as intermediaries between the MEMS structures and the substrate. These layers control and stabilize the electrode gaps, preventing unwanted capacitance shifts while maintaining the electrical connection functionality. The sacrificial dielectric layer specifically ensures consistent gap dimensions during manufacturing.
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 design stabilizes capacitance gaps and prevents pattern sticking, enhancing the reliability and manufacturing precision of MEMS devices by reducing deformation-induced offsets and plasma damage.
Implementation Method 1
The dual MEMS structure design incorporates dielectric layers between MEMS structures and a cover layer, using chemical dry etching to form patterns
Data Source
AI summary
A micro electro mechanical system (MEMS) includes a circuit substrate, a first MEMS structure disposed over the circuit substrate, and a second MEMS structure disposed over the first MEMS structure.