MEMS Resonator Bonding Stack for Vacuum Sealing Under Degassing Heat
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Resonance devices produced by MEMS technology face challenges in maintaining a high vacuum state due to outgassing, which is exacerbated by high-temperature heat treatment during degassing, leading to thermal diffusion and deviation of eutectic composition in eutectic bonding.
Innovation Solution
A resonance device with a bonding portion composed of a eutectic layer of germanium and a metal mainly containing aluminum, a titanium layer, and an aluminum oxide film, which are consecutively arranged to prevent thermal diffusion and ensure airtight sealing, allowing for high-temperature degassing without compromising vacuum integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature heat treatment is performed for degassing, then outgassing is reduced and vacuum quality improves, but thermal diffusion occurs causing deviation of eutectic composition and bonding failure
Solution Approach 1:
A diffusion preventing layer is introduced as an intermediary between the eutectic bonding layer and the substrate. This layer acts as a barrier that blocks thermal diffusion during high-temperature degassing, preventing composition deviation while allowing the bonding to proceed. The diffusion preventing layer is specifically designed with low wettability to AuSn to stop solder diffusion into the functional layer.
Solution Approach 2:
The bonding portion is segmented into multiple functional layers: a eutectic bonding layer for sealing, a diffusion preventing layer for blocking thermal diffusion, and a functional layer for device operation. This segmentation allows each layer to perform its specific function independently, enabling high-temperature degassing without compromising bonding integrity.
2Reliability
If eutectic bonding is performed to seal the vibration space, then airtightness is achieved, but thermal diffusion during heat treatment causes deviation of eutectic composition
Solution Approach 1:
The diffusion preventing layer serves as a mediator that separates the eutectic bonding layer from the substrate. During heat treatment, this intermediary layer blocks the diffusion path, preventing thermal diffusion while maintaining the airtight seal through the eutectic bonding layer.
Solution Approach 2:
The bonding portion uses a composite structure combining multiple materials with different properties: the eutectic bonding layer provides sealing, the diffusion preventing layer (with low wettability to AuSn) provides diffusion barrier functionality, and the functional layer provides device operation capability. This composite structure resolves the contradiction between airtightness and composition stability.
3Manufacturing precision
If diffusion preventing layer is added to prevent thermal diffusion, then eutectic composition stability is maintained, but device complexity increases
Solution Approach 1:
The invention changes the material parameter of the diffusion preventing layer by selecting materials with specific properties (low wettability to AuSn). This parameter change enables the layer to function as a diffusion barrier without requiring complex structural designs, thus maintaining simplicity while achieving composition stability.
Solution Approach 2:
The diffusion preventing layer is a simple intermediary structure that can be integrated into the existing bonding process. By using a single functional layer with appropriate material properties, the invention avoids the need for complex multi-layer structures or additional processing steps, thereby limiting the increase in device complexity.
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
The solution effectively maintains a high vacuum in the vibration space of the resonator by preventing thermal diffusion and outgassing, enhancing the airtightness and reducing production costs through the use of titanium and aluminum oxide films.
Implementation Method 1
when heat treatment for degassing is performed at a high temperature, thermal diffusion occurs easily to cause, for example, the deviation of a eutectic composition
Implementation Method 2
bonding the metal layer of the first layer to the germanium layer of the second layer by eutectic bonding so as to seal a vibration space of the resonator
Data Source
AI summary
A resonance device that includes a MEMS substrate including a resonator, an upper cover, and a bonding portion that bonds the MEMS substrate to the upper cover to seal a vibration space of the resonator. The bonding portion includes a eutectic layer composed of a eutectic alloy of germanium and a metal mainly containing aluminum, a first titanium (Ti) layer, a first aluminum oxide film, and a first conductive layer consecutively arranged from the MEMS substrate to the upper cover.