IC-Compatible MEMS Resonator with Planar Electrodes
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Solution Overview
Problem
The integration of Microelectromechanical Systems (MEMS) structures with Complementary Metal-Oxide-Semiconductor (CMOS) architectures faces challenges, such as temperature thresholds that cause irreversible degradation of semiconductor ICs and limitations in fabricating MEMS devices with optimal performance, particularly due to the requirement for virgin substrates and increased parasitics in one-port configurations.
Innovation Solution
An IC-compatible MEMS structure is developed with a resonating member and distinct driver and sensor electrodes formed in the same plane, electrically coupled with interconnects, allowing for reduced parasitics and enhanced performance, fabricated using processes at temperatures below 450°C to ensure compatibility and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MEMS structures are integrated with CMOS architectures using BEOL processing, then the MEMS device can be incorporated into the semiconductor IC, but the resonating member and driver/sensor electrode must be in different levels of interconnects, increasing parasitics and fabrication complexity
Solution Approach 1:
The patent merges the driver electrode and sensor electrode into the same interconnect level, eliminating the need for separate levels. This consolidation reduces the overall interconnect structure complexity and minimizes parasitic effects while maintaining the MEMS device integration with CMOS architectures.
Solution Approach 2:
The patent transitions from a three-dimensional stacked configuration (different levels) to a two-dimensional planar configuration (same level). By arranging both electrodes at the same interconnect level, the design reduces vertical complexity and parasitic coupling while achieving optimal device performance.
2Reliability
If semiconductor IC is fabricated first, then the IC can be integrated with MEMS structure, but the IC degrades at temperature thresholds above which irreversible degradation occurs
Solution Approach 1:
The patent performs preliminary actions by fabricating the MEMS structure first on a virgin substrate, then integrating the semiconductor IC with the already-formed MEMS device. This sequence allows the IC to be processed at lower temperatures that do not cause irreversible degradation, while the MEMS structure can withstand subsequent processing.
Solution Approach 2:
The patent inverts the conventional fabrication sequence by forming the MEMS structure before integrating the semiconductor IC. This reversal allows the IC to be processed under conditions that preserve its integrity, avoiding exposure to temperatures that would cause irreversible degradation.
3Manufacturing precision
If MEMS device is fabricated on virgin substrate, then optimal performance can be achieved, but the requirement for virgin substrates limits integration flexibility
Solution Approach 1:
The patent segments the fabrication process into distinct stages: first forming the MEMS structure on a virgin substrate to ensure optimal performance, then separately integrating the semiconductor IC. This segmentation allows each component to be optimized independently while maintaining overall integration flexibility.
Solution Approach 2:
The patent performs preliminary action by pre-forming the MEMS structure on a virgin substrate before IC integration. This preliminary step ensures optimal MEMS performance is achieved on the virgin substrate, while subsequent IC integration can proceed with greater flexibility since the critical MEMS fabrication is already complete.
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 enables the formation of reliable and high-performance MEMS devices integrated with CMOS circuits, reducing parasitics and maintaining device integrity across temperature thresholds, thus addressing the limitations of existing integration methods.
Implementation Method 1
A MEMS resonator is formed above and coupled with the plurality of interconnects. In one embodiment, the MEMS resonator is comprised of a member and a pair of electrodes
Implementation Method 2
A MEMS resonator is comprised of a member, a driver electrode and a sensor electrode
Implementation Method 3
the driver electrode and the sensor electrode are electrically coupled with the plurality of interconnects
Data Source
AI summary
An IC-compatible MEMS structure and a method to form such a structure are described. In an embodiment, an integrated circuit having a MEMS device is formed. The structure comprises a plurality of semiconductor devices formed on a substrate. A plurality of interconnects is above and coupled with the plurality of semiconductor devices, incorporating the plurality of semiconductor devices into the integrated circuit. A MEMS resonator is formed above, and coupled with, the plurality of interconnects. In one embodiment, the MEMS resonator is comprised of a member and a pair of electrodes. The pair of electrodes is electrically coupled with the plurality of interconnects.