Sensor Support Structure Segmentation for CMOS Integration
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Solution Overview
Problem
The integration of pressure sensors with CMOS ASICs is complicated and expensive due to the need for multiple mask planes and a complex process for removing a sacrificial layer, which limits sensor size and deflection ratio, causing undesirable non-linear sagging and size constraints.
Innovation Solution
A sensor structure with a plurality of independent support elements, such as 'foot'-like structures, supports a moveable element, allowing easier removal of the sacrificial layer and improved deflection ratio, enabling easier integration with CMOS processing and reducing the number of necessary mask planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polycrystalline silicon lamella structure is integrated into CMOS process, then sensor functionality is achieved, but manufacturing complexity increases due to requiring at least five mask planes and complicated sacrificial layer removal
Solution Approach 1:
The support structure is segmented into multiple independent support elements (feet) rather than a continuous frame, allowing the sacrificial layer to be removed through simple etch access without complex masking. Each support element is independently formed, simplifying the integration process with CMOS fabrication.
Solution Approach 2:
The invention extracts and removes the complex sacrificial layer removal process by designing support elements that allow direct etch access. The sacrificial layer is removed through simple etching via openings in the isolation trenches, eliminating the need for multiple mask planes and complicated processing steps.
2Stability of the object's composition
If a frame structure is used to support the lamella, then structural stability is provided, but the deflection ratio decreases and non-linear sagging occurs
Solution Approach 1:
The continuous frame structure is segmented into discrete support elements (feet) positioned at specific locations. This segmentation allows the membrane to deflect more freely between support points, improving the deflection ratio and reducing non-linear sagging while maintaining structural stability through strategic placement of support elements.
Solution Approach 2:
Instead of uniform continuous support, the support is localized to specific discrete points (support elements). This local quality approach provides stability only where needed while allowing maximum deflection in the active sensing area, improving linearity and deflection ratio.
3Manufacturing precision
If multiple mask planes are used for sensor fabrication, then precise structure formation is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
The formation of support elements and isolation trenches is merged into a single etching process step. The support elements are formed by etching through the membrane and isolation layer simultaneously, eliminating the need for separate masking and etching steps that would otherwise be required, thus reducing mask plane requirements while maintaining precision.
Solution Approach 2:
The support elements serve multiple functions: they provide structural support, define the cavity boundaries, and enable sacrificial layer removal. This multi-functionality eliminates the need for separate structures for each function, reducing the number of mask planes and manufacturing steps required.
Data Source
AI summary
Embodiments relate to sensors and more particularly to structures for and methods of forming sensors that are easier to manufacture as integrated components and provide improved deflection of a sensor membrane, lamella or other movable element. In embodiments, a sensor comprises a support structure for a lamella, membrane or other movable element. The support structure comprises a plurality of support elements that hold or carry the movable element. The support elements can comprise individual points or feet-like elements, rather than a conventional interconnected frame, that enable improved motion of the movable element, easier removal of a sacrificial layer between the movable element and substrate during manufacture and a more favorable deflection ratio, among other benefits.