Suspended MEMS Getter for Localized Activation
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Solution Overview
Problem
Current technologies for controlling ambient pressure and gas composition in hermetic packages for MEMS and optoelectronic devices face challenges due to high activation temperatures required for thin-film getters, which can damage devices and increase packaging complexity and costs, especially as package sizes shrink.
Innovation Solution
A MEMS-based microdevice with a locally-heated suspended structure for thin-film getters, integrated with CMOS circuitry and temperature sensors, allowing for selective heating without affecting surrounding components, enabling activation at lower temperatures and multiple reactivations without impairing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high activation temperatures (400-1000°C) are used for thin-film getters, then the getter can effectively capture gas species and maintain vacuum, but the semiconductor devices and MEMS microstructures integrated in the packages are damaged
Solution Approach 1:
The package is divided into two separate compartments: a first compartment containing the semiconductor device and a second compartment containing the thin-film getter. This segmentation allows the getter to be activated at high temperatures without exposing the semiconductor device to damaging thermal conditions, as the device remains in a thermally isolated compartment.
Solution Approach 2:
A partition wall with a small aperture connects the two compartments, acting as an intermediary that allows gas molecules to pass from the device compartment to the getter compartment while providing thermal isolation. The small aperture restricts heat transfer while maintaining vacuum integrity through getter activation.
2Reliability
If the whole package is heated to activation temperature, then the getter material can diffuse passivation layer and capture gas species, but a great deal of thermal stress is generated to the assembly
Solution Approach 1:
The package is divided into two separate compartments: a first compartment containing the semiconductor device and a second compartment containing the thin-film getter. This segmentation allows the getter to be activated at high temperatures without exposing the semiconductor device to damaging thermal conditions, as the device remains in a thermally isolated compartment.
Solution Approach 2:
High temperature activation is applied locally only to the getter compartment rather than the entire package. The partition wall with small aperture creates a localized heating zone where thermal stress is confined to the getter area, preventing widespread thermal stress across the entire assembly.
3Reliability
If conventional electrically-activated getters are used, then gas composition and pressure can be controlled, but the getters become too bulky to fit in shrinking microcavities
Solution Approach 1:
The patent employs a thin-film getter deposited on a substrate within the second compartment. This thin-film configuration provides the necessary gas absorption capability while occupying minimal volume, allowing the getter to fit within shrinking microcavity packages without compromising pressure control functionality.
4Object-affected harmful factors
If localized heating methods such as laser heating or electrical Joule heating are used, then thermal damage to devices can be reduced, but the complexity of the packages and costs increase
Solution Approach 1:
The package is divided into two separate compartments: a first compartment containing the semiconductor device and a second compartment containing the thin-film getter. This segmentation allows the getter to be activated at high temperatures without exposing the semiconductor device to damaging thermal conditions, as the device remains in a thermally isolated compartment.
Solution Approach 2:
The patent changes the thermal parameter distribution by creating a temperature gradient between the two compartments. The getter compartment can be heated to activation temperature while the device compartment remains at lower temperatures, achieving selective thermal treatment without requiring complex localized heating mechanisms.
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 allows for precise control of pressure and gas composition within hermetic packages at lower temperatures, reducing thermal stress and packaging complexity, while maintaining device performance and extending the lifetime of MEMS and optoelectronic devices.
Implementation Method 1
Heating allows the getter material to reach its activation temperature, which is typically in the range of 400° C. to 1000° C. Such elevated temperatures permit the diffusion into the bulk of the getter material of the passivation layer that grows on the surface of the getter, thus leaving a fresh surface area ready for further capture of different gas species.
Implementation Method 2
Gas-absorbing materials, commonly known as getters, are currently used to control the pressure inside sealed microcavities.
Implementation Method 3
the thin-film getter material is deposited on structures having various shapes and it is heated either by bake out, by an electrical resistor, by RF (radio-frequency) heating or by absorption of laser radiation
Data Source
AI summary
A MEMS (micro-electro-mechanical system) getter microdevice for controlling the ambient pressure inside the hermetic packages that enclose various types of MEMS, photonic, or optoelectronic devices. The getter microdevice revolves around a platform suspended at a height above a substrate, and which is supported by supporting legs having low thermal conductance. Layers are deposited on the platform, such layers including a properly patterned resistor element, a heat-spreading layer and, finally, a thin-film getter material. When an electrical current flows through it, the resistor element heats the thin-film getter material until it reaches its activation temperature. The getter material then absorbs the gas species that could be present in the hermetic package, such gas species possibly impairing the operation of the devices housed in the packages while reducing their lifetime. The weak thermal conductance between the platform and the substrate helps in preventing damages to the surrounding devices when the MEMS getter microdevice is heated at its activation temperature, and it reduces the electrical power required for reaching the activation temperature as well.