Monolithic CMOS-Photonic Integration for APD-ALED Arrays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face issues such as high source/drain junction capacitance, crosstalk, limited Time-Of-Flight measurements, and inability to operate in avalanche mode or emit light, due to their design and substrate limitations.
Innovation Solution
The development of monolithically integrated avalanche devices that can operate as both sensors and emitters, using layouts with dual functionality Pixels/Lixels, allowing for software-controlled operation as Avalanche Photo-Diodes (APDs) or Avalanche Light Emitting Diodes (ALEDs), and enabling dynamic control of signal grouping and pixel size for improved resolution and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional CMOS image sensors use built-in pn-junction formed by source/drain and potential-well regions, then the device structure is simple and manufacturing is easy, but the source/drain junction capacitance is high resulting in low charge-to-voltage conversion efficiency
Solution Approach 1:
The patent separates the photodetection function from the CMOS circuitry by introducing dedicated photodiode structures with optimized pn-junctions. The photodiodes are implemented as distinct regions with tailored doping profiles and geometries, decoupling the photo-detection performance from the constraints of standard CMOS source/drain junctions. This segmentation allows independent optimization of junction capacitance for high charge-to-voltage conversion efficiency while maintaining standard CMOS manufacturing processes.
2Device complexity
If conventional CMOS image sensors use standard layout and peripheral circuitry, then the device complexity is low and manufacturing is simple, but signal aggregation from multiple pixels is not enabled limiting resolution versus signal strength trade-off
Solution Approach 1:
The patent implements a dual-mode readout architecture where the same pixel array and peripheral circuitry can operate in two distinct modes: individual pixel readout for high resolution, and aggregated pixel readout for enhanced signal strength. The peripheral circuitry includes configurable summing nodes and multiplexers that can dynamically combine signals from multiple pixels according to software-controlled patterns. This universal design enables the system to adapt between resolution and signal strength requirements without requiring separate hardware paths.
3Reliability
If conventional CMOS and BiCMOS technologies are used, then the manufacturing process is established and reliable, but the junction cannot operate in avalanche mode or emit light
Solution Approach 1:
The patent introduces localized regions with specialized material compositions and structural characteristics within the CMOS device. Specifically, certain junctions are engineered with optimized doping concentrations, depletion region widths, and material layers (such as SiGe or other bandgap-engineered materials) that enable avalanche breakdown and light emission. These local modifications are confined to specific photodetector regions while the rest of the CMOS circuitry maintains standard manufacturing specifications, ensuring overall manufacturing reliability while enabling advanced functionalities in targeted areas.
4Ease of manufacture
If conventional CMOS image sensors are designed with fixed pixel structure, then the manufacturing process is simple, but dynamic control of pixel grouping and variable pixel size is not possible
Solution Approach 1:
The patent implements a dynamically reconfigurable pixel array where the functional grouping of pixels can be changed during operation through software control. The peripheral circuitry includes programmable multiplexers and summing nodes that can be configured to aggregate signals from different combinations of pixels based on real-time requirements. This dynamic reconfiguration capability allows the system to adapt pixel grouping patterns, effective pixel size, and readout modes on-the-fly without any physical reconfiguration or complex manufacturing processes, maintaining manufacturing simplicity while enabling operational flexibility.
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
Enables efficient charge-to-voltage conversion, reduces crosstalk, supports Time-Of-Flight measurements, and allows for light emission, enhancing the performance and versatility of CMOS image sensors by leveraging direct bandgap materials and advanced substrate technologies.
Implementation Method 1
Avalanche Photo-Diodes (APDs)
Implementation Method 2
operated in the avalanche mode
Implementation Method 3
indirect bandgap materials, such as silicon and germanium, can emit light when pn-junctions are operated in the avalanche mode
Implementation Method 4
Avalanche Light Emitting Diodes (ALEDs)
Data Source
AI summary
Several detailed layout designs are disclosed, for the monolithic integration of avalanche devices in large arrays, that can be operated as Avalanche Photo-Diodes (APDs) or Avalanche Light Emitting Diodes (ALEDs) depending only on the applied bias conditions, which can be software-controlled from peripheral circuitry. If the deposited films have direct bandgaps, then the devices can emit light even in the absence of avalanche operation. In particular, the layouts according to the invention comprise a sensor/emitter matrix achieved through the replication of basic Pixel/Lixel cells.