MEMS Sealed Cavity Double Release Process
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Solution Overview
Problem
In Micro Electro Mechanical Systems (MEMS) devices, the sealing process often results in gas emission from sealing materials, altering the operating pressure and contaminating components, leading to impaired device performance.
Innovation Solution
A double release process is implemented, involving the formation of a first sealing layer and a sacrificial capping layer, with release holes allowing simultaneous removal of sacrificial materials to create upper and lower chambers, followed by a second release to form a release chamber, enabling controlled sealing and minimizing gas emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing layer is used to seal the MEMS cavity, then the cavity can be sealed and shut, but gases are emitted from the sealing material into the MEMS cavity, altering operating pressure and contaminating components
Solution Approach 1:
The patent divides the sealing structure into multiple segments: a first sealing layer for initial sealing, a sacrificial capping layer for temporary protection, and a second sealing layer for final sealing. This segmentation allows each layer to serve a specific function in the sealing process, with the sacrificial layer being removed later to prevent gas emission issues.
Solution Approach 2:
The patent applies preliminary action by forming the sacrificial capping layer before the final sealing process. This sacrificial layer is deposited over the first sealing layer and sacrificial material, then removed in a subsequent release process. This preliminary structure prevents direct contact between sealing materials and the MEMS cavity during high-thermal-budget processes, thereby preventing gas emission.
2Ease of manufacture
If high thermal budget processes are performed after sealing layer formation, then semiconductor wafer processing can be completed, but the sealing material deforms and emits gases into the MEMS cavity
Solution Approach 1:
The sacrificial capping layer acts as an intermediary protective barrier between the sealing layer and the MEMS cavity during high-thermal-budget processes. This intermediate layer absorbs the thermal stress and prevents direct deformation and gas emission from the sealing material into the cavity, while still allowing the thermal processes to be completed for semiconductor wafer fabrication.
Solution Approach 2:
The sacrificial capping layer and sacrificial material are designed as temporary, disposable elements that are intentionally removed after serving their protective function. These short-living components enable the completion of high-thermal-budget processes without compromising the sealing integrity, as they are removed in a controlled release process after the thermal processes are complete.
3Ease of manufacture
If moisture reacts with the sealing material, then bubbles form in the sealing layer, but this causes outgassing into the MEMS cavity
Solution Approach 1:
The sacrificial capping layer serves as an intermediary barrier that prevents moisture from reaching and reacting with the sealing material. This intermediate protective layer blocks the chemical reaction between moisture and sealing material, thereby preventing bubble formation and subsequent outgassing into the MEMS cavity while still allowing the sealing layer to be formed.
Solution Approach 2:
The sacrificial capping layer is a temporary protective element that is removed after serving its protective function. It prevents moisture-induced reactions during the manufacturing process, then is removed in a controlled release process to prevent any potential outgassing issues from affecting the MEMS cavity.
Data Source
AI summary
Disclosed is a MEMS device having lower, upper and release chambers with a similar pressure and/or a similar gaseous chemistry. The MEMS device includes a top MEMS plate and a bottom MEMS plate. The MEMS device also includes a lower chamber between the bottom MEMS plate and the top MEMS plate, and an upper chamber between the top MEMS plate and a first sealing layer. The MEMS device further includes a release chamber between the top MEMS plate and a second sealing layer, the release chamber allowing gaseous content of the upper and/or the lower chambers to be released. Also disclosed is a double release method for releasing gaseous content of the upper and/or the lower chambers.