Metallic Getter Structure for MEMS Sensors
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Solution Overview
Problem
Conventional getter devices for micromechanical components, such as MEMS rotation-rate sensors, face limitations in achieving low internal pressures due to residual gas friction and degassing, which restrict the mechanical quality of the sensors.
Innovation Solution
A metallic getter structure within a micromechanical component's cavity that can be heated using a defined electric current to evaporate the material in a controlled manner, allowing for precise reduction of internal pressure through gas absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a pasty getter material is applied in a planar manner in the cap, then the internal pressure can be reduced to approx. 1 mbar, but the mechanical quality is limited by residual gas friction and degassing
Solution Approach 1:
The patent changes the physical state of the getter material from pasty to metallic, and the activation method from chemical to thermal evaporation. This parameter change enables controlled material distribution and repeated activation cycles, improving both pressure reduction and mechanical quality simultaneously
Solution Approach 2:
The metallic getter structure can be evaporated repeatedly using controlled electric current pulses, allowing periodic reactivation to maintain low pressure over time. This periodic action overcomes the limitation of single-use pasty getters and sustains mechanical quality
2Quantity of substance
If sensor wafer and cap wafer are bonded in a chamber under desired internal pressure, then internal pressures greater than approx. 1 mbar can be set, but residual gas and surface degassing limit the achievable minimum pressure
Solution Approach 1:
The metallic getter structure is pre-installed in the cap wafer before bonding, positioned to face the rotation-rate sensor cavity. This preliminary placement enables immediate gettering action upon activation, effectively counteracting residual gas and surface degassing effects from the bonding process
Solution Approach 2:
The getter material undergoes phase transition from solid metallic structure to vapor phase during evaporation, then condenses to cover surfaces and trap residual gas. This phase transition mechanism effectively removes harmful residual gases and prevents re-outgassing
3Quantity of substance
If conventional vacuum systems with evaporated metallic getter materials are used, then vacuum can be produced, but the process lacks precision and control for micromechanical applications
Solution Approach 1:
The getter structure is integrated with electric current supply terminals that enable controlled evaporation based on feedback from pressure sensors. This closed-loop control achieves precise pressure regulation tailored to micromechanical component requirements, unlike conventional uncontrolled evaporation
Solution Approach 2:
The patent replaces conventional thermal evaporation methods with electric current-induced evaporation. This substitution provides precise temporal and spatial control over the gettering process, enabling manufacturing precision required for micromechanical applications
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 solution enables a precise and controlled reduction of internal pressure in micromechanical components, enhancing the mechanical quality and operational life of sensors by allowing for fine adjustments and repeated gettering processes.
Implementation Method 1
the getter structure is heatable using a defined electric current
Implementation Method 2
it being possible to evaporate the material of the getter structure in a defined manner
Implementation Method 3
a metallic getter structure that is situated in a cavity of the micromechanical component... chemically activated... binds the residual gas
Data Source
AI summary
A getter device for a micromechanical component, having a metallic getter structure that is situated in a cavity of the micromechanical component. The getter structure is heatable using a defined electric current. It is possible to evaporate the material of the getter structure in a defined manner.