Monolithic MEMS Thermal Isolation via Glass Flexures
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Solution Overview
Problem
Existing MEMS devices face performance degradation due to temperature variations, and prior methods for thermal isolation increase complexity and cost by requiring separate fabrication and attachment of thermal isolation stages, which can lead to mechanical drift and instability.
Innovation Solution
A method for monolithic fabrication of MEMS devices using a composite substrate with embedded sacrificial structures in glass, forming thermally isolating glass flexures to integrate MEMS devices directly on a thermal isolation stage, reducing power consumption and complexity by using glass flexures with low thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate thermal isolation stage is fabricated and attached to the MEMS die, then thermal isolation is achieved, but device complexity and fabrication cost increase
Solution Approach 1:
The patent merges the thermal isolation stage with the MEMS die by fabricating both structures within the same device layer using a monolithic process. The isolation stage is formed as an integrated part of the MEMS device structure, eliminating the need for separate fabrication and attachment processes while maintaining effective thermal isolation through the use of low-thermal-conductivity materials and geometric design.
2Reliability
If a separate thermal isolation stage is attached by soldering or bonding, then thermal isolation is achieved, but long term stability degrades due to mechanical drift
Solution Approach 1:
The patent eliminates mechanical attachment between separate components by integrating the thermal isolation stage directly into the MEMS die structure. Both the MEMS device and the isolation stage are formed as monolithic structures within the same device layer, removing attachment points that would otherwise be subject to mechanical drift and degradation over time.
Solution Approach 2:
The thermal isolation stage is formed during the initial fabrication process before the MEMS device is completed. The isolation structure is preliminarily created as part of the substrate preparation, ensuring stable thermal isolation from the beginning of device operation without requiring subsequent attachment steps that could introduce instability.
3Reliability
If active temperature control is implemented without thermal isolation, then temperature stabilization is achieved, but power consumption increases
Solution Approach 1:
The patent segments the device structure into a thermally isolated MEMS device region and the surrounding substrate, separated by the isolation stage. This segmentation creates thermal boundaries that confine heat within the device region, reducing thermal leakage to the substrate and thereby lowering the power required for active temperature control while maintaining stabilization.
Solution Approach 2:
The thermal isolation stage acts as an intermediary structure between the MEMS device and the substrate. It provides a low-thermal-conductivity pathway that mediates heat transfer, allowing temperature stabilization of the device while minimizing thermal coupling to the substrate, thus reducing the power consumption required for active temperature control.
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 allows for low-power active temperature control of MEMS devices, maintaining stability and accuracy across a wide temperature range while reducing fabrication complexity and cost.
Implementation Method 1
The thermal isolation stage is anchored to a package by a plurality of bonds. The package includes a glass frame and a plurality of glass flexures connecting the glass frame to the thermal isolation stage.
Data Source
AI summary
A method for fabricating a thermally isolated microelectromechanical system (MEMS) structure is provided. The method includes processing a first wafer of a first material with a glass wafer to form a composite substrate including at least one sacrificial structure of the first material and glass; forming a MEMS device in a second material; forming at least one temperature sensing element on at least one of: the composite substrate; and the MEMS device; and etching away the at least one sacrificial structure of the first material in the composite substrate to form at least one thermally isolating glass flexure. The MEMS device is thermally isolated on a thermal isolation stage by the at least one thermally isolating glass flexure. The at least one temperature sensing element in on a respective at least one of: the thermal isolation stage; and the MEMS device.