MEMS Grid Etching for Structural Control
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Solution Overview
Problem
Traditional MEMS fabrication methods using silicon on insulator (SOI) wafers face limitations in structural design flexibility and require extensive handling, leading to potential damage and increased costs due to the need for wafer thinning and separate die preparation, which complicates the process and results in heavier devices.
Innovation Solution
A method combining surface micromachining and bulk micromachining techniques, involving deep trench etching and thermal oxide insulation to create MEMS devices, allowing for precise structural control and separation from the substrate without the need for wafer thinning or separate die preparation, using anisotropic and isotropic etching to achieve desired thickness and structural properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SOI wafer fabrication is used, then device separation and die preparation are achieved, but extensive handling is required leading to potential damage and increased costs
Solution Approach 1:
The patent combines the device separation and die preparation steps into a single integrated process. Deep trenches are etched through the substrate to simultaneously achieve both device separation and die preparation, eliminating the need for separate handling steps and reducing the risk of damage while simplifying the overall fabrication process
2Length of moving object
If wafer thinning is performed, then device thickness is reduced, but additional processing steps are required increasing complexity and costs
Solution Approach 1:
The patent extracts the thickness control function from the separate wafer thinning process and integrates it directly into the trench etching step. By etching deep trenches through the substrate, the desired device thickness is achieved simultaneously with device separation, eliminating the need for additional wafer thinning processing steps
3Ease of operation
If separate die preparation is performed, then individual dies are obtained, but handling and processing time increase
Solution Approach 1:
The patent merges the die preparation step with the device separation step by etching deep trenches that simultaneously accomplish both tasks. This integrated approach allows individual dies to be obtained directly during the separation process, eliminating the need for separate die preparation steps and reducing overall fabrication time
4Strength
If more material is used in device structure, then structural strength is improved, but device weight increases
Solution Approach 1:
The patent utilizes the deep trench structure to create a porous or lattice-like device architecture. The trenches remove excess material to reduce device weight while the remaining structural elements maintain necessary mechanical strength. This approach allows optimization of the strength-to-weight ratio by strategically positioning material only where structurally required
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 simplifies MEMS device fabrication, reduces material usage and handling-related issues, results in lighter devices with customizable structural properties, and eliminates the need for additional processing steps like wafer thinning and die preparation, thereby reducing costs and improving device performance.
Implementation Method 1
anisotropically etching a plurality of holes into a substrate wafer
Implementation Method 2
isotropically etching into the substrate wafer through the plurality of holes to separate the MEMS device from the substrate wafer
Implementation Method 3
The insulator is unlike the regular passivated layer, and it is thermal grown oxide
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3C
AI summary
A system and method for manipulating the structural characteristics of a MEMS device including etching a plurality of holes into the surface of a MEMS device, wherein the plurality of holes comprise one or more geometric shapes determined to provide specific structrual characteristics desired in the MEMS device.