Stacked 3D Image Sensor Pixels for Higher Integration Density
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Solution Overview
Problem
The challenge in the development of three-dimensional (3D) image sensors is the larger pixel size, which increases the overall device size and reduces integration density, necessitating a method to minimize pixel size while maintaining efficiency.
Innovation Solution
A 3D image sensor design featuring a first substrate with an upper pixel and a second substrate with a lower pixel, connected by bonding conductors, allowing for a pixel array configuration where pixels are divided between substrates, reducing horizontal area and improving integration density through inclined alignment of bonding conductors and pixel structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If depth sensors use larger pixels to capture depth images, then depth sensing capability is improved, but device size increases and integration density decreases
Solution Approach 1:
The patent transitions from a planar pixel arrangement to a three-dimensional stacked architecture where upper and lower pixels are vertically arranged on different substrates. This vertical stacking enables depth sensing functionality without increasing the horizontal footprint of the device, effectively resolving the contradiction between depth sensing capability and device size.
Solution Approach 2:
The pixel array is segmented into multiple independent pixel units stacked vertically across different substrates. Each pixel unit contains both upper and lower pixels that can independently capture light, allowing the system to achieve depth sensing through vertical separation rather than horizontal expansion.
2Reliability
If more bonding conductors are added to connect stacked substrates, then electrical connectivity between pixels is improved, but manufacturing complexity increases
Solution Approach 1:
The bonding conductors serve multiple functions simultaneously: they provide electrical connectivity between corresponding pixels on different substrates, act as alignment references during bonding, and enable the vertical stacking architecture. This multi-functionality reduces the need for additional specialized components and simplifies the overall manufacturing process.
3Measurement precision
If pixels are arranged in a dense array, then resolution is improved, but pixel size must be reduced which complicates manufacturing
Solution Approach 1:
By moving from a two-dimensional dense pixel array to a three-dimensional stacked configuration, the patent achieves high resolution through vertical multiplication of pixel layers rather than horizontal compression. This allows each pixel to maintain adequate size while the overall system achieves high resolution through the combination of multiple stacked pixel arrays.
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 design effectively reduces pixel size, enhances integration density, and improves resolution by expanding pixels vertically while minimizing horizontal area, thereby addressing the size and efficiency issues in existing 3D image sensors.
Implementation Method 1
the upper pixel including a photoelectric element and first and second photogates connected to the photoelectric element
Data Source
AI summary
A three-dimensional (3D) image sensor includes a first substrate having an upper pixel. The upper pixel includes a photoelectric element and first and second photogates connected to the photoelectric element. A second substrate includes a lower pixel, which corresponds to the upper pixel, that is spaced apart from the first substrate in a vertical direction. The lower pixel includes a first transfer transistor that transmits a first signal provided by the first photogate. A first source follower generates a first output signal in accordance with the first signal. A second transfer transistor transmits a second signal provided by the second photogate. A second source follower generates a second output signal in accordance with the second signal. First and second bonding conductors are disposed between the first and second substrates and electrically connect the upper and lower pixels.