Dual-Band Image Sensor Pixel Layout for Simultaneous Readout
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Solution Overview
Problem
Existing dual-band image sensors face challenges in fabrication complexity, low yield, and difficulty in scaling up for larger formats, particularly in simultaneous mode operations. Additionally, prior art does not effectively address unipolar two-color designs with thin barrier layers.
Innovation Solution
The proposed solution involves a simultaneous dual-band image sensor architecture that includes a substrate with a common ground, Band 1 and Band 2 absorber layers, a barrier layer, and a ring opening in each pixel. This configuration allows for simultaneous signal collection from both bands with a simpler and higher-yielding fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simultaneous dual-band image sensor uses traditional fabrication processes with diffusion/implantation steps or metal bridges, then electrical connection between layers is achieved, but fabrication complexity increases and yield decreases
Solution Approach 1:
The patent removes the complex diffusion/implantation steps and metal bridge structures from the fabrication process. Instead, it uses a simplified approach where the middle layer contact is formed directly through the absorber layers using standard semiconductor processing, eliminating the need for intermediate metal bridges and complex doping steps while maintaining electrical connectivity.
Solution Approach 2:
The patent divides the pixel structure into distinct functional layers (first absorber layer for first band, second absorber layer for second band, middle layer for signal processing) that can be independently processed and connected. This segmentation allows each layer to be optimized separately and connected through simple vias, reducing overall fabrication complexity.
2Adaptability or versatility
If a simultaneous dual-band image sensor requires two or three bumps per pixel for electrical connection, then both bands can be sensed simultaneously, but fabrication becomes very challenging
Solution Approach 1:
The patent combines the electrical connection functions for both bands into a single bump structure per pixel. The middle layer contact serves as a common connection point that interfaces with both the first and second absorber layers, eliminating the need for separate bumps for each band and significantly simplifying the fabrication process.
Solution Approach 2:
The middle layer contact structure is designed to serve multiple functions: it provides electrical connection for both Band 1 and Band 2 signals, acts as a common ground reference, and enables simultaneous readout of both bands. This multi-functional design reduces the number of required interconnect structures per pixel.
3Reliability
If prior art uses contact in middle layer with bridging to top layer, then electrical connection is established, but process complexity increases hampering scaling
Solution Approach 1:
Instead of creating complex metal bridges from the middle layer up to the top layer, the patent inverts the approach by forming simple vertical vias from the top absorber layers down to the middle layer contact. This inversion simplifies the interconnect architecture and makes the process more amenable to scaling to larger formats and higher pixel densities.
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
The described architecture enables scalable and high-yield fabrication of simultaneous dual-band image sensors, allowing for efficient simultaneous collection of signals from two electromagnetic bands. This approach simplifies the fabrication process and addresses the limitations of prior art, particularly for unipolar two-color designs.
Implementation Method 1
Band 1 absorber layer on the common ground layer, a barrier layer on the Band 1 absorber layer, a Band 2 absorber layer on the barrier layer
Data Source
Figure 1A~1L
Figure 2A~2B
Figure 3A
AI summary
A simultaneous dual-band image sensor having a plurality of pixels includes a substrate, a common ground on the substrate, wherein each pixel includes a Band 1 absorber layer on the common ground layer, a barrier layer on the Band 1 absorber layer, a Band 2 absorber layer on the barrier layer, a ring opening in the pixel formed by a removed portion of the Band 2 absorber layer, a removed portion of the barrier layer and a removed portion of the Band 1 absorber layer, wherein the ring opening does not extend through the Band 1 absorber layer, a first contact on a portion of the Band 2 absorber layer inside the ring, and a second contact on a portion of the Band 2 absorber layer outside the ring. The Band 1 absorber layer and the Band 2 absorber layer are n-type, or the Band 1 absorber layer and the Band 2 absorber layer are p-type.