3D Stacked Imaging Structure With Oxide Semiconductor Pixel Circuits
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Solution Overview
Problem
Current imaging devices face challenges in achieving high-density, high-capacity semiconductor integration, miniaturization, low noise, high-speed operation, low illuminance capability, wide temperature range usage, high aperture ratio, and high reliability, particularly in three-dimensional integration structures.
Innovation Solution
The development of an imaging device with a stacked structure incorporating a photoelectric conversion element and transistors with oxide semiconductors and silicon, where metal layers are bonded using the same main component, allowing for three-dimensional integration and division driving, while maintaining low off-state current and high reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If three-dimensional integration structure is adopted to increase integration density, then semiconductor integration capacity is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent transitions from two-dimensional planar integration to three-dimensional stacked integration by bonding multiple semiconductor substrates vertically. This dimensional change allows significantly higher integration density by utilizing the vertical space above each pixel circuit substrate, enabling independent formation and bonding of multiple functional layers without increasing lateral footprint.
Solution Approach 2:
The imaging device is divided into separate functional substrates (first substrate with pixel circuits, second substrate with signal processing circuits, third substrate with memory circuits) that are manufactured independently and then bonded together. This segmentation allows each substrate to be optimized separately and simplifies the manufacturing process by enabling parallel production of different functional modules.
2Area of stationary object
If pixel circuit area is reduced to increase aperture ratio, then light receiving efficiency is improved, but transistor layout becomes more difficult
Solution Approach 1:
The patent moves transistor layout from a two-dimensional constraint to a three-dimensional solution by placing transistors on different substrates. The pixel circuit transistors are formed on the first substrate while signal processing and memory transistors are formed on separate second and third substrates, eliminating the need to pack all transistors into the limited pixel area and enabling high aperture ratio.
Solution Approach 2:
The circuit functions are segmented across multiple substrates: pixel circuit transistors on the first substrate, signal processing transistors on the second substrate, and memory transistors on the third substrate. This segmentation removes the constraint of fitting all transistors within the pixel area, allowing maximum aperture ratio while maintaining ease of transistor layout on each individual substrate.
3Reliability
If oxide semiconductor transistors are used to reduce off-state current, then data retention is improved, but transistor performance may be limited
Solution Approach 1:
The patent applies different semiconductor material qualities to different functional regions: oxide semiconductor transistors are used specifically in the pixel circuit substrate where low off-state current and high data retention are critical for charge storage, while other substrates can use different materials optimized for their specific functions. This local optimization allows oxide semiconductors to provide their advantage in data retention without requiring them to perform all circuit functions.
Solution Approach 2:
The imaging device uses a composite structure combining oxide semiconductor transistors in the pixel circuits with other semiconductor materials in signal processing and memory circuits. This composite material approach allows each substrate to use materials optimized for its specific function, achieving both low off-state current in pixel circuits and high-speed operation in processing circuits.
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 the creation of a high-resolution imaging device with reduced noise, capable of operating at low illuminance and across a wide temperature range, with a high aperture ratio and improved reliability, facilitating efficient data retention and high-speed operation.
Implementation Method 1
The first layer includes a photoelectric conversion element
Data Source
AI summary
An imaging device having a three-dimensional integration structure is provided. A first structure including a transistor including silicon in an active layer or an active region and a second structure including an oxide semiconductor in an active layer are fabricated. After that, the first and second structures are bonded to each other so that metal layers included in the first and second structures are bonded to each other; thus, an imaging device having a three-dimensional integration structure is formed.