SPAD Prism Package Layout for High-Aspect-Ratio Line Arrays
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Solution Overview
Problem
Conventional image sensors suffer from limited functionality, including inability to determine object distance and lower than desired image quality and resolution, which is addressed by incorporating single-photon avalanche diodes (SPADs) for enhanced light detection and depth sensing.
Innovation Solution
The implementation of SPADs in imaging systems, which include passive and active quenching circuitry to detect single photons and measure photon time-of-flight for 3D imaging, along with silicon photomultipliers to increase dynamic range and resolution by grouping SPADs in arrays and using prisms to redirect light across multiple silicon dice for high aspect ratio arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-photon avalanche diodes (SPADs) are used for single photon detection, then sensitivity to incident light is improved, but device complexity increases due to required quenching circuitry and specialized packaging
Solution Approach 1:
Multiple silicon dice containing SPAD arrays are integrated onto a single substrate and packaged together with inter-die optical coupling, combining multiple sensing elements into a unified device that achieves high sensitivity while distributing complexity across modular components
Solution Approach 2:
Optical coupling elements such as lenses or microlens arrays are introduced as intermediaries between the SPAD arrays and incident light, enabling efficient photon detection without requiring complex direct coupling structures, thus maintaining sensitivity while simplifying the overall device architecture
2Measurement precision
If high aspect ratio silicon photomultiplier arrays are implemented, then dynamic range and resolution are improved, but manufacturing difficulty increases due to fragility and alignment challenges
Solution Approach 1:
The silicon photomultiplier array is divided into multiple smaller silicon dice with lower individual aspect ratios, which are then assembled in a multi-die package. This segmentation reduces the fragility and manufacturing difficulty of each individual die while maintaining the overall high aspect ratio and performance of the complete array through precise inter-die optical coupling
Solution Approach 2:
The system transitions from a single-plane high aspect ratio array to a three-dimensional multi-die stacked configuration, where multiple lower-aspect-ratio dice are arranged in layers with optical coupling between dies. This dimensional change enables manufacturing of individual dice while achieving the desired overall array geometry and performance
3Ease of manufacture
If multiple silicon dice are used to form high aspect ratio arrays, then manufacturing feasibility is improved, but device complexity increases due to staggered arrangement and inter-die coupling requirements
Solution Approach 1:
Multiple silicon dice are merged onto a single substrate with their respective SPAD arrays optically coupled to shared optical elements or light paths. This merging approach distributes the manufacturing complexity across standard-sized dice while achieving the functional equivalent of a high aspect ratio array through the combined structure
Solution Approach 2:
The package substrate and optical coupling elements are designed to serve multiple functions simultaneously: mechanical support for multiple dice, optical alignment reference, and light routing between dies and external sources. This multi-functionality reduces the number of separate components needed, thereby reducing overall device complexity despite the multi-die configuration
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 solution enables improved sensitivity in low light conditions, increased dynamic range, and higher resolution imaging by effectively detecting single photons and measuring photon time-of-flight, while maintaining manufacturing feasibility through the use of multiple lower-aspect-ratio silicon dice and light redirecting prisms.
Implementation Method 1
Each pixel typically includes a photosensitive element (such as a photodiode) that receives incident photons (light) and converts the photons into electrical signals
Implementation Method 2
using prisms to redirect light across multiple silicon dice for high aspect ratio arrays
Implementation Method 3
measure photon time-of-flight for 3D imaging
Data Source
AI summary
A semiconductor package may include a line array of single-photon avalanche diodes (SPADs). The line array of single-photon avalanche diodes may be split between multiple silicon dice. The silicon dice may have a staggered arrangement, with prisms on the package lid redirecting incident light to the silicon dice. The silicon dice may alternate between a first side of the package substrate and a second side of the package substrate. The prisms may alternate between a first structure that redirects incident light to the first side of the package substrate and a second structure that redirects incident light to the second side of the package substrate. The silicon dice may overlap to allow satisfactory alignment between the silicon dice and the prisms.