Monolithic Inertial Sensor Integration on CMOS Substrate
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Solution Overview
Problem
Incumbent micromachined inertial technologies face limitations in integration level with CMOS, scalability, and leveraging IC foundries' capabilities, resulting in larger form factor, higher parasitics, higher power consumption, and higher costs compared to macro electromechanical sensors.
Innovation Solution
The integration of inertial mechanical devices on top of a CMOS substrate using IC-foundry compatible processes, involving a thick silicon layer addition, patterning for mechanical structures, and encapsulation with a thick insulating layer at the wafer level, enabling monolithic integration and reducing chip size, parasitics, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk or surface micromachining techniques are used for MEMS inertial sensors, then the sensors can be fabricated with micromachined structures, but the level of integration with CMOS is limited and IC foundries' capability cannot be leveraged
Solution Approach 1:
The patent merges MEMS inertial sensor fabrication with standard CMOS IC fabrication processes by using the same silicon-on-insulator substrate and compatible processing steps. The mechanical sensing structures, electronic circuitry, and interconnects are all formed on the same substrate using integrated process flows that leverage IC foundries' existing capabilities for high-volume manufacturing.
Solution Approach 2:
The invention creates a universal fabrication platform that can produce both MEMS inertial sensors and CMOS electronic circuits on the same substrate using standard IC foundry processes. This multi-functional approach allows the same manufacturing infrastructure to serve dual purposes, enabling levering of IC foundries' capability and capacity for sensor production.
2Manufacturing precision
If incumbent MEMS fabrication processes are used, then micromachined structures can be created, but the form factor is larger compared to integrated approaches
Solution Approach 1:
The patent transitions from lateral expansion of separate MEMS and CMOS components to vertical integration on the same substrate. By stacking mechanical sensing structures, electronic circuits, and interconnect layers in three dimensions, the design achieves high integration density with minimal lateral footprint, dramatically reducing the overall chip form factor.
3Measurement precision
If separate MEMS and CMOS fabrication approaches are used, then each component can be optimized independently, but parasitics and power consumption increase
Solution Approach 1:
The patent combines the mechanical sensing structures and electronic readout circuits into a single integrated device on the same substrate. This integration minimizes parasitic capacitances and inductances that arise from external interconnects, reduces signal path lengths, and lowers overall power consumption compared to separate discrete components.
4Reliability
If incumbent MEMS technologies are used, then inertial sensing can be achieved, but the cost is higher compared to integrated IC approaches
Solution Approach 1:
The invention creates a universal fabrication platform that leverages IC foundries' existing high-volume manufacturing infrastructure, equipment, and process expertise. By using standard CMOS-compatible processes on silicon-on-insulator substrates, the approach enables cost-effective production through economies of scale and shared manufacturing resources.
Data Source
AI summary
The present invention relates to integrating an inertial mechanical device on top of a CMOS substrate monolithically using IC-foundry compatible processes. The CMOS substrate is completed first using standard IC processes. A thick silicon layer is added on top of the CMOS. A subsequent patterning step defines a mechanical structure for inertial sensing. Finally, the mechanical device is encapsulated by a thick insulating layer at the wafer level.Comparing to the incumbent bulk or surface micromachined MEMS inertial sensors, the vertically monolithically integrated inertial sensors have smaller chip size, lower parasitics, higher sensitivity, lower power, and lower cost.