Quantum Dot Image Sensor Pixel Scaling via Shared Transistors
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Solution Overview
Problem
Current image sensors face challenges in achieving high spatial resolution while maintaining cost-effectiveness, as reducing pixel size is hindered by the need for smaller process geometries and custom implants, which are costly and complex.
Innovation Solution
The implementation of a quantum dot-based image sensor with tightly pitched electrodes and shared transistors, combined with a readout circuit design that allows for time-domain multiplexing and reduced transistor count, enables smaller pixel sizes without compromising spatial resolution or increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to increase spatial resolution, then spatial resolving power is improved, but manufacturing complexity and cost increase due to smaller process geometries and custom implants
Solution Approach 1:
The patent transitions from planar pixel structures to vertically stacked three-dimensional pixel structures. Multiple photodetector layers are stacked vertically, each detecting different wavelengths, with shared readout circuitry below. This vertical stacking enables higher spatial resolution without proportionally reducing pixel footprint, as the increased capacity is achieved in the vertical dimension rather than requiring smaller horizontal features.
Solution Approach 2:
The patent implements shared readout circuitry that serves multiple photodetector layers simultaneously. A single readout circuit can read out signals from multiple stacked photodetector layers, reducing the overall transistor count per pixel and simplifying the manufacturing process. This multi-functional approach allows the same circuit structure to handle multiple detection functions without requiring separate custom implants for each layer.
2Measurement precision
If pixel size is reduced to increase spatial resolution, then spatial resolving power is improved, but manufacturing cost increases due to custom implants and smaller process geometries
Solution Approach 1:
The patent achieves increased spatial resolution through vertical stacking of photodetector layers rather than reducing horizontal pixel dimensions. This approach allows standard manufacturing processes to be used for creating multiple detection layers, avoiding the need for costly custom implants and advanced lithography required for smaller planar pixels.
Solution Approach 2:
The patent combines multiple photodetector layers into a single integrated structure with shared readout circuitry. By merging the readout functions for multiple layers into common circuits, the overall device complexity and manufacturing cost are reduced compared to implementing separate readout circuits for each pixel or layer.
3Device complexity
If transistor count per pixel is reduced through sharing, then device complexity is reduced, but signal-to-noise ratio may worsen due to shared readout circuits
Solution Approach 1:
The patent compensates for potential signal-to-noise ratio degradation from shared readout circuits by increasing the total detection capacity in the vertical dimension. Multiple stacked photodetector layers provide redundant detection paths, and signals can be integrated across layers before readout, maintaining signal integrity while using shared circuits.
Solution Approach 2:
The patent segments the detection function across multiple vertical layers while sharing the readout function horizontally. Each photodetector layer can be independently optimized for specific wavelength ranges, and signals from multiple layers can be selectively read out or combined, allowing flexibility in managing signal-to-noise ratio while maintaining low device complexity.
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 allows for a significant reduction in pixel size, enhancing spatial resolution and signal-to-noise ratio while reducing power consumption and maintaining cost-effectiveness by using standard digital signal processing and smaller process geometries.
Implementation Method 1
The image sensor includes a quantum dot layer formed over a substrate, a first electrode, a second electrode, and a third electrode. The quantum dot layer is configured to detect electromagnetic radiation and generate an electrical signal in response to the electromagnetic radiation.
Data Source
AI summary
In various embodiments, methods and related apparatuses for sealing down pixel sizes in quantum film-based image sensors are disclosed. In one embodiment, an image sensor circuit is disclosed that includes circuit includes an optically sensitive layer, a first pixel having a first electrode coupled to a first region of optically sensitive layer, a second pixel having a second electrode coupled to a second region of optically sensitive layer, and a readout circuit having at least one transistor that is shared among the first pixel and the second pixel. In a first time interval, the transistor is used in a readout of a signal related to illumination of the first pixel over an integration period. During a second time interval, the transistor is used in a readout of a signal related to illumination of the second pixel over an integration pixel. The signals thusly read constitute a time-domain multiplexed (TDM) signal.