Getter Structure With Variable Thickness Zones For Vacuum Encapsulation
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Solution Overview
Problem
Current getter structures for encapsulating microsystems like MEMS and NEMS face challenges in achieving and maintaining a controlled vacuum environment due to difficulties in thermal activation temperature alignment with sealing processes, leading to inefficient gas pumping and increased production costs.
Innovation Solution
A getter structure comprising adjacent parts of different thicknesses and surface grain densities, allowing for adjustable thermal activation temperature and pumping capacity, produced in a single deposition step, enabling modulation of thermal activation during the sealing cycle and subsequent gas pumping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a getter material with high pumping capacity is used, then the vacuum level in the cavity is improved, but the thermal activation temperature may not align with the sealing process temperature
Solution Approach 1:
The getter structure is divided into multiple zones with different thicknesses (first zone with thickness h1, second zone with thickness h2 where h1 > h2). Each zone has different surface grain density and thus different thermal activation characteristics. This local variation in structure allows the getter to operate effectively across a range of temperatures, aligning with the sealing process while maintaining high pumping capacity.
2Productivity
If the getter material is thermally activated before sealing is complete, then gas pumping occurs during sealing, but the pumping capabilities are reduced after sealing
Solution Approach 1:
The getter structure utilizes gradual thickness variation from the first zone (h1) to the second zone (h2) to create a gradient in thermal activation behavior. This parameter change allows different portions of the getter to activate at different temperatures during the sealing process, enabling controlled gas pumping during sealing while preserving sufficient pumping capacity for post-sealing operation.
3Reliability
If additional heat treatment is performed after sealing to activate the getter, then the thermal activation temperature mismatch is resolved, but production time and cost increase
Solution Approach 1:
The getter structure is designed so that the sealing process itself provides the thermal activation energy needed. The multi-zone thickness configuration ensures that the getter activates during the sealing temperature range, merging the sealing operation with the getter activation process. This eliminates the need for separate post-sealing heat treatment steps, reducing production time and cost.
4Adaptability or versatility
If multilayer deposits or particular metal alloys are used to achieve specific thermal activation temperatures, then the thermal activation temperature range is covered, but production cost increases
Solution Approach 1:
Instead of using different materials or multilayer structures, the invention achieves different thermal activation characteristics by varying the local thickness of a single getter material layer. The first zone has greater thickness (h1) and the second zone has lesser thickness (h2), creating local structural quality differences that result in different surface grain densities and thermal activation temperatures, thereby reducing material costs while maintaining versatility.
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 reduces production costs and allows for flexible vacuum level management within encapsulation, enabling efficient gas absorption and adsorption across a range of thermal activation temperatures, from 250°C to 450°C, during and after encapsulation.
Implementation Method 1
materials are used, called getter materials, which trap the gas molecules contaminating the gaseous environment in the cavity (for example of the H2O, CO2, N2, O2, H2, etc.) by chemical reaction with them
Implementation Method 2
Such a getter material therefore makes it possible to carry out gaseous pumping by absorption and/or adsorption of these gaseous molecules
Implementation Method 3
During this treatment, the chemical species trapped on the surface (in particular of the C, N and O type) are dissolved by diffusion in the material to expose the metal surface which is then able to adsorb other gaseous molecules
Implementation Method 4
A getter material carries out a gaseous pumping after having undergone a heat treatment (the getter material is heated to a certain temperature) called thermal activation
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
The structure has a getter portion (103) including two adjacent getter material parts (104, 106) that are arranged one beside the other on a support (102), and a substrate including a semiconductor such as silicon. The material parts exhibit different thicknesses and include cylindrical grains and surface grain densities, which are different from one another. The getter portion comprises a getter material layer consisting of titanium or zirconium. The material layer covers other material layers of the structure, and is protected by a protective layer. An independent claim is also included for a method for producing a getter structure.