Getter Design for Vacuum MEMS Devices
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Solution Overview
Problem
The existing processes for forming microelectromechanical systems (MEMS) devices face challenges such as low getter efficiency, high getter activation temperature, increased cavity pressure, and device instability due to impurities in the getter layer and poor bond interfaces between discrete layers, leading to outgassing and bond ring leakage.
Innovation Solution
A method involving the formation of a reactive layer with impurities on a cap substrate, followed by an unreactive layer, and an annealing process to interdiffuse materials, creating a getter structure with a filter layer that separates the reactive material from impurities, allowing for low-temperature bonding and improved vacuum sealing, stability, and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a getter layer is formed using conventional sputtering processes, then the getter layer is created, but impurities are introduced into the getter layer resulting in low getter efficiency
Solution Approach 1:
The patent extracts and removes impurities from the getter layer through a selective etching process. The etch selectively removes impurities while preserving the reactive getter material, thereby improving getter efficiency without sacrificing the getter layer's functionality. This directly addresses the contradiction by extracting the harmful impurities that were introduced during conventional sputtering.
Solution Approach 2:
The patent changes the chemical composition parameters of the getter layer by introducing a specific composition ratio of reactive material to impurities, and by using selective etching to alter the impurity concentration. This parameter change transforms the getter layer from an impurity-contaminated state to a high-purity state, resolving the contradiction between manufacturing precision and reliability.
2Strength
If high temperature bonding is used to bond substrates, then strong bonding is achieved, but outgassing occurs and cavity pressure increases
Solution Approach 1:
The patent performs preliminary cleaning and preparation of the bonding surfaces before bonding, and uses selective etching to remove impurities that would cause outgassing. This preliminary action ensures that when bonding occurs, there is minimal outgassing even if moderate temperatures are used, thus preventing the harmful effect before it can occur.
Solution Approach 2:
The patent changes the bonding temperature parameter from high temperature to moderate temperature bonding, combined with improved surface preparation. This parameter change allows achieving sufficient bond strength without triggering outgassing, thus resolving the contradiction between bond strength and outgassing.
3Device complexity
If discrete layers are bonded together, then device structure is formed, but poor bond interfaces cause bond ring leakage
Solution Approach 1:
The patent applies local quality improvement by focusing on the bond interface regions specifically. Selective etching is applied to improve the local quality of bonding surfaces, creating optimal bonding conditions at the interfaces between discrete layers. This ensures high-quality bond interfaces while maintaining the overall multi-layer device structure.
4Reliability
If getter activation is performed at high temperature, then gettering function is activated, but device stability decreases due to thermal stress
Solution Approach 1:
The patent changes the getter activation temperature parameter from high temperature to lower temperature activation. This is achieved through improved getter layer purity and composition, allowing the gettering function to be activated at temperatures that do not cause thermal stress, thus maintaining device stability while achieving reliable gettering.
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 enhances getter efficiency, reduces cavity pressure, and maintains a vacuum seal at lower temperatures, increasing the stability and performance of MEMS devices by utilizing a filter layer to pass reactive material while blocking impurities, thus improving the overall performance and endurance of the integrated chip.
Implementation Method 1
perform an anneal to interdiffuse the reactive material and the unreactive material at an interface between the getter layer and the unreactive layer
Implementation Method 2
The filter layer is configured to block the impurities from passing from the first side to the second side of the filter layer
Implementation Method 3
The reactive material getters an outgas species within the cavity
Data Source
AI summary
Some embodiments of the present disclosure are related to an integrated chip including a first substrate underlying a second substrate. The first and second substrates at least partially define a cavity. An absorptive layer is disposed within the cavity and comprises a reactive mater. An absorption-enhancement layer is disposed along the absorptive layer and within the cavity. The absorption-enhancement layer is configured to pass the reactive material from a top surface to a bottom surface of the absorption-enhancement layer.