Segmented FPA Architecture for Infrared Sensor Yield
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Solution Overview
Problem
The increasing complexity of monolithic focal plane arrays (FPAs) in infrared imaging devices leads to decreased yield and increased costs, along with larger die sizes, which are problematic for applications in small devices, due to limitations in semiconductor fabrication processes and the inclusion of additional circuitry such as analog-to-digital converters (ADCs) in the read-out integrated circuit (ROIC).
Innovation Solution
A segmented focal plane array architecture is implemented, where a top die with an array of infrared sensors and a portion of the ROIC is electrically coupled with a bottom die containing the remainder of the ROIC via inter-die connections, allowing for separate semiconductor processes for each die and a smaller footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional circuitry such as ADCs is included in the ROIC to compensate for non-uniformities and temperature-dependent variations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The FPA is divided into multiple separate dies: a first die containing the bolometer array and a second die containing the ROIC with additional circuitry such as ADCs. This segmentation allows the ROIC to include complex compensation circuits without increasing the complexity of the bolometer fabrication process, as each die can be optimized and fabricated independently using appropriate processes.
2Measurement precision
If more circuits and components are included in the ROIC, then measurement precision is improved, but manufacturing precision decreases
Solution Approach 1:
By separating the bolometer array from the ROIC into different dies, the invention allows each component to be fabricated using optimized processes appropriate to its specific requirements. The first die can be fabricated using processes optimized for bolometer performance, while the second die can use processes optimized for high-precision circuit fabrication, thereby maintaining high manufacturing precision for both components independently.
Solution Approach 2:
The invention changes the fabrication parameter by using different semiconductor fabrication processes for the first die and second die. This allows each die to be manufactured with process parameters optimized for its specific function, improving overall manufacturing precision and yield compared to using a single monolithic process for all components.
3Measurement precision
If additional circuitry is included in the ROIC, then measurement precision is improved, but area of the device increases
Solution Approach 1:
The ROIC is segmented into a second die that is separate from the first die containing the bolometer array. This allows the ROIC with its additional precision-improving circuitry to be placed on a separate substrate, enabling more flexible area utilization. The first die maintains a compact size optimized for the bolometer array, while the second die contains the expanded ROIC functionality.
Solution Approach 2:
The invention transitions from a two-dimensional monolithic layout to a three-dimensional stacked architecture where the first die and second die are positioned at different vertical levels. This dimensional change allows both dies to be compact in their respective footprints while maintaining full functionality, as the area constraint is relieved by utilizing the vertical dimension for inter-die connections.
4Device complexity
If a monolithic FPA architecture is used, then device complexity is reduced, but manufacturing precision decreases
Solution Approach 1:
The FPA is segmented into multiple independently fabricable dies that can be produced using optimized processes for each component type. This segmentation improves manufacturing precision and yield by allowing each die to be fabricated with process parameters specifically tuned for its function, rather than requiring all components to be manufactured simultaneously in a single complex monolithic process.
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 enhances the yield and reduces the size of FPAs, facilitating their use in small devices while maintaining performance, by allowing for independent design and fabrication of each die, thus overcoming the limitations of monolithic architectures.
Implementation Method 1
a first die comprising an array of active bolometers adapted to receive infrared (IR) radiation from a scene
Data Source
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AI summary
Various techniques are provided for implementing a segmented focal plane array (FPA) of infrared sensors. In one example, a system includes a segmented FPA. The segmented FPA includes a top die having an array of infrared sensors (e.g., bolometers). The top die may also include a portion of a read-out integrated circuit (ROIC). The segmented FPA also includes a bottom die having at least a portion of the ROIC. The top and the bottom dies are electrically coupled via inter-die connections. Advantageously, the segmented FPA may be fabricated with a higher yield and a smaller footprint compared with conventional FPA architectures. Moreover, the segmented FPA may be fabricated using different semiconductor processes for each die.