Wafer Level Package Getter Layer Arrangement for MEMS Vacuum
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Solution Overview
Problem
Current MEMS vacuum packaging technologies face challenges in maintaining ultra-high vacuum conditions due to the high volume-to-surface ratio and the limitations of zirconium-based getters, which are flammable and explosive.
Innovation Solution
A layer arrangement is developed using surface engineering techniques to enhance the gettering properties of non-zirconium materials like titanium by applying a sacrificial layer with a negative Gibbs free energy of oxide formation, optimizing the deposition process, and increasing the surface area of the getter film to achieve vacuum levels of 10 mTorr or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zirconium-based getters are used to achieve ultra-high vacuum conditions, then the vacuum level can be maintained at 10 mTorr or less, but the getter materials become flammable and explosive
Solution Approach 1:
The patent extracts the harmful property (flammability) from the getter system by removing zirconium and replacing it with non-flammable materials like titanium, while preserving the essential vacuum-gettering function through alternative mechanisms
Solution Approach 2:
The patent employs a sacrificial layer that can be removed after serving its purpose during fabrication, allowing the use of materials that provide excellent gettering during manufacturing but may not be suitable for long-term operation, thus solving the safety issue
2Object-affected harmful factors
If non-zirconium getter materials like titanium are used, then flammability is reduced, but the gettering capability is insufficient due to oxidation and contamination
Solution Approach 1:
The patent introduces a sacrificial layer as an intermediary between the titanium getter layer and the external environment. This sacrificial layer protects the titanium from oxidation and contamination during fabrication, enabling the titanium to maintain its gettering capability without the flammability issues of zirconium
Solution Approach 2:
The patent creates a composite structure consisting of a titanium getter layer combined with a sacrificial layer. This composite approach allows the system to benefit from titanium's non-flammability while the sacrificial layer compensates for titanium's lower inherent gettering capability by preventing oxidation
3Productivity
If wafer level packaging is used to reduce cost, then manufacturing efficiency increases, but maintaining vacuum conditions becomes more difficult due to high volume to surface ratio
Solution Approach 1:
The patent employs a porous silicon dioxide layer as a sacrificial material that can be selectively removed. This porous structure allows for effective outgassing during the vacuum pumping phase while maintaining structural integrity, thereby helping to achieve and maintain vacuum conditions in the wafer-level packaged MEMS devices
Solution Approach 2:
The patent utilizes changes in the physical and chemical parameters of the sacrificial layer (such as porosity, thickness, and composition) to optimize its performance. By carefully controlling these parameters, the sacrificial layer effectively manages outgassing and protects the vacuum environment during the critical wafer-level packaging process
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 effectively maintains ultra-high vacuum conditions, is cost-effective, and safer than zirconium-based solutions, while being compatible with CMOS technology, facilitating the integration of MEMS devices with electronics.
Implementation Method 1
This technology utilizes the unique property of getter materials to sorb the residual gases trapped in the device during the manufacturing process and maintains the pressure at a very low level for the required lifetime by limiting the gas flux.
Implementation Method 2
Metals such as zirconium (Zr), titanium (Ti), tantalum (Ta) and yttrium (Y) used in the getters are capable of dissolving their own chemically formed oxides, nitrides and carbides in the solid-state form at elevated temperatures.
Implementation Method 3
The surface engineering technique affords optimum coverage of the getter layer surface with a sacrificial layer and also the optimization of the getter material deposition process that would result in a getter film with highly porous or rough appearance.
Data Source
AI summary
The invention relates to a layer arrangement and a wafer level package comprising the layer arrangement, and in particular, the layer arrangement comprises a getter layer and further comprises a sacrificial layer. The wafer level package may be used in microelectromechanical systems (MEMS) packaging at a vacuum level of about 10 mTorr or less such as close to 1 mTorr (i.e. MEMS vacuum packaging).