Stacked Pixel Circuit Layout for Light-Shielded Solid-State Imaging
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Solution Overview
Problem
Existing solid-state imaging devices face challenges in expanding dynamic range, achieving electronic shutter function, and realizing analog/digital conversion at each pixel, while requiring a secure light shielding structure to prevent light from entering the pixel additional circuit.
Innovation Solution
A solid-state imaging device is designed with a photoelectric conversion unit, transfer unit, and floating node on a first substrate, and a pixel additional circuit, including a switch and capacitance, on a second substrate, with a light shielding member on the first substrate to reduce light transmission to the pixel additional circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pixel additional circuit is provided to each pixel to expand dynamic range and achieve electronic shutter function, then functionality is improved, but light shielding structure becomes more complex and secure light shielding is difficult to establish
Solution Approach 1:
The device is divided into two separate substrates: first substrate containing photoelectric conversion unit and light shielding structure, second substrate containing pixel additional circuit. This segmentation allows independent optimization of light shielding and circuit functionality without mutual interference.
Solution Approach 2:
The pixel additional circuit is moved from the same plane as the photoelectric conversion unit to a different substrate (second dimension), enabling light shielding to be implemented more effectively on the first substrate without constraining the circuit design on the second substrate.
2Reliability
If light shielding structure is strengthened to prevent light from entering pixel additional circuit, then light shielding performance is improved, but photoelectric conversion area is reduced
Solution Approach 1:
By separating the light shielding structure and pixel additional circuit onto different substrates, the light shielding structure can be optimized without compromising the photoelectric conversion area on the first substrate, while the pixel additional circuit on the second substrate remains fully functional.
3Adaptability or versatility
If photoelectric conversion unit and pixel circuit are disposed on different substrates, then integration flexibility is improved, but electrical connection complexity increases
Solution Approach 1:
A microlens array is introduced as an intermediary optical element between the photoelectric conversion unit on the first substrate and the pixel additional circuit on the second substrate. This intermediary helps guide and focus light while the electrical connections are established through controlled interfaces between substrates, managing the complexity of inter-substrate connections.
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 configuration enables advanced signal processing at each pixel without reducing the photoelectric conversion area, improving light shielding performance and expanding the dynamic range while maintaining high sensitivity and image linearity.
Implementation Method 1
a photoelectric conversion unit, a transfer unit configured to transfer signal electric charges of the photoelectric conversion unit
Implementation Method 2
a first light shielding member disposed on the first substrate and configured to reduce light transmitted through the photoelectric conversion unit to enter the pixel additional circuit
Data Source
AI summary
In a solid-state imaging device, a photoelectric conversion unit, a transfer transistor, and at least a part of electric charge holding unit, among pixel constituent elements, are disposed on a first semiconductor substrate. An amplifying transistor, a signal processing circuit other than a reset transistor, and a plurality of common output lines, to which signals are read out from a plurality of pixels, are disposed on a second semiconductor substrate.