CMOS BEOL MEMS Structure for Compact Inertial Sensor Integration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing processes for MEMS devices are bespoke and costly, leading to high costs, large size, long time-to-market, and limited volume production capabilities, as they cannot be integrated with CMOS processes, which are more economical and efficient.
Innovation Solution
Utilizing the back-end-of-line (BEOL) materials of a CMOS process, specifically through vapor HF etching (vHF) to create MEMS devices within the CMOS die, employing a bottom and top metal plane with small holes and interleaved anchor structures to control the MEMS cavity, and designing springs and proof masses with specific shapes to minimize size and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bespoke MEMS manufacturing processes are used, then MEMS devices can be fabricated with specific functional requirements, but cost increases significantly
Solution Approach 1:
The patent combines MEMS device fabrication with standard CMOS manufacturing processes by forming MEMS structures (cavities, movable elements, interconnection layers) using the same BEOL metal layers and processing steps already present in CMOS production. This merging eliminates the need for separate bespoke MEMS manufacturing, thereby reducing cost while maintaining functional reliability
Solution Approach 2:
The patent makes the CMOS manufacturing process universal by enabling it to produce both standard integrated circuits and MEMS devices using the same process flow. The BEOL metal layers serve multiple functions: electrical interconnection for CMOS circuits and structural components for MEMS devices, allowing a single manufacturing line to produce both device types
2Reliability
If separate MEMS and CMOS wafers are packaged together, then functional requirements are met, but package size increases
Solution Approach 1:
The patent merges MEMS and CMOS devices into a single integrated wafer by forming MEMS structures within the CMOS die using the same BEOL layers. This eliminates the need for separate MEMS and CMOS wafers and their associated packaging, thereby significantly reducing package size while maintaining all required functions
Solution Approach 2:
The patent nests MEMS structures within the CMOS die architecture by forming cavities and movable elements using the existing BEOL metal layers. The MEMS components are embedded within the same substrate and interconnection structure as the CMOS circuitry, creating a compact integrated device
3Reliability
If bespoke MEMS processes are used, then device performance can be optimized, but time-to-market increases
Solution Approach 1:
The patent performs preliminary actions by forming MEMS structures during the standard CMOS manufacturing process before final packaging. The cavities, movable elements, and interconnection layers are created using the same BEOL processing steps already scheduled in the CMOS production timeline, eliminating the need for subsequent separate MEMS fabrication and reducing time-to-market
4Adaptability or versatility
If separate MEMS and CMOS production lines are used, then manufacturing flexibility is maintained, but volume production capability is limited
Solution Approach 1:
The patent merges MEMS and CMOS production into a single manufacturing line by using the same CMOS fabrication process for both device types. The BEOL metal layers serve dual purposes for both CMOS circuits and MEMS structures, allowing volume production of integrated devices without requiring separate specialized MEMS production facilities
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 reduces the size and cost of MEMS devices, enhances performance by minimizing parasitic capacitance, and allows for high-volume production, enabling integration with CMOS processes, thus addressing the limitations of bespoke MEMS manufacturing.
Implementation Method 1
The inventive approaches use a bottom metal plane and a top metal plane with an array of small holes to allow the vHF to go inside the MEMS cavity. A key inventive concept is to limit the overall MEMS size on the layout to between 50μm and 150μm
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A MEMS device formed using the materials of the BEOL of a CMOS process where a post-processing of vHF and post backing was applied to form the MEMS device and where a total size of the MEMS device is between 50um and 150um. The MEMS device may be implemented as an inertial sensor among other applications.