Micromechanical Element Grid Structure for Cavity Closure
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Solution Overview
Problem
Existing methods for producing micromechanical elements face challenges in efficiently and effectively closing access holes after sacrificial layer removal, leading to longer processing times, material contamination, and potential damage to the functional layer due to the use of critical gases and materials.
Innovation Solution
The method involves creating a grid structure in the cover layer to constrict and facilitate faster closure of the cavity, allowing for the use of closure materials that grow predominantly vertically, reducing contamination and enabling a wider selection of gases that do not adversely affect the functional layer, while forming a supporting structure for increased stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a large opening is created for sacrificial layer removal, then access to the sacrificial layer is improved, but the closure process becomes longer and more complex
Solution Approach 1:
The opening in the closure cap is divided into multiple smaller openings arranged in a grid pattern. This segmentation allows the closure layer to be deposited more efficiently across multiple small areas rather than one large area, reducing the overall closure time and complexity while maintaining adequate access for sacrificial layer removal.
2Reliability
If the closure process takes a long time, then complete closure is achieved, but material deposits on the functional layer causing contamination
Solution Approach 1:
By dividing the opening into a grid of smaller openings, the closure layer deposits more rapidly onto the closure cap surface rather than extending deep into the cavity. This segmented approach completes the closure process faster, preventing material from reaching and contaminating the functional layer while still achieving complete closure.
Solution Approach 2:
The grid structure is prepared in advance on the closure cap before the closure layer deposition. This preliminary structuring guides the closure material to deposit primarily on the cap surface and prevents uncontrolled flow into the cavity, ensuring complete closure without contamination of the functional layer.
3Reliability
If critical gases are used for closure, then effective sealing is achieved, but the functional layer is adversely affected
Solution Approach 1:
The segmented grid structure enables the use of less aggressive closure materials or gases that would not damage the functional layer. The multiple small openings provide sufficient sealing capability even with milder materials, eliminating the need to use critical gases that could harm the functional layer.
4Ease of manufacture
If the opening diameter is large, then sacrificial layer removal is easier, but closure reliability decreases
Solution Approach 1:
The large opening is segmented into multiple smaller openings in a grid pattern. This provides adequate access for sacrificial layer removal through the distributed openings while the collective coverage of all openings ensures reliable closure. The grid structure maintains closure reliability by distributing the sealing function across multiple points rather than relying on a single large opening.
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 results in a faster, more reliable closure process with reduced internal pressure, improved quality of the micromechanical structure, lower power consumption, and better performance of the sensor by minimizing material deposition on the functional layer and allowing for a greater choice of closure materials.
Implementation Method 1
applying a closure layer at least on the grid structure of the cover layer for the purpose of closing the access to the cavity
Implementation Method 2
A gas is then introduced through said access holes and removes the sacrificial layer, for example by etching
Data Source
AI summary
A method for producing a micromechanical element includes producing a micromechanical structure, the micromechanical structure having: a functional layer for a micromechanical element, a sacrifical layer at least partly surrounding the functional layer, and a closure cap on the sacrifical layer. The method further includes applying a cover layer on the micromechanical structure. The method further includes producing a grid structure in the cover layer. The method further includes producing a cavity below the grid structure, as access to the sacrifical layer. The method further includes at least partly removing the sacrifical layer. The method further includes applying a closure layer at least on the grid structure of the cover layer for the purpose of closing the access to the cavity.