Stacked Image Pickup Circuit Layout for Chip Area and Dark Current
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Solution Overview
Problem
Conventional image pickup devices face challenges in reducing the chip area of peripheral circuits without degrading pixel section performance, leading to increased costs and non-uniform dark current due to heat generated by peripheral circuits.
Innovation Solution
The solution involves forming the pixel section on one semiconductor substrate and the column circuits on another, with the column circuits located under the pixel section, allowing for efficient arrangement and reducing non-uniformity of dark current by dispersing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the peripheral circuit section area is increased to improve image pickup device function, then the device performance is improved, but the chip area is increased leading to higher costs
Solution Approach 1:
The patent utilizes a three-dimensional stacked configuration where the pixel section and peripheral circuit section are formed on different substrates at different vertical levels. This allows the peripheral circuits to be positioned underneath the pixel section, effectively using the vertical dimension to accommodate additional functionality without increasing the horizontal chip area footprint.
2Ease of manufacture
If the pixel section and peripheral circuit section are formed on the same substrate, then the manufacturing process is simplified, but the peripheral circuits generate heat that causes non-uniform dark current
Solution Approach 1:
The patent divides the image pickup device into two separate substrates: a first substrate containing the pixel section and a second substrate containing the peripheral circuit section. This segmentation physically separates the heat-generating peripheral circuits from the sensitive pixel section, eliminating the dark current non-uniformity problem while maintaining manufacturing feasibility through a systematic multi-substrate fabrication process.
Solution Approach 2:
The patent introduces connection portions that electrically connect the pixel section on the first substrate with the peripheral circuit section on the second substrate. These connection portions act as intermediaries, enabling signal transmission between the separated sections while maintaining physical distance to minimize thermal interference.
3Object-generated harmful factors
If the pixel section and peripheral circuit section are formed on separate chips, then heat generation from peripheral circuits is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functional sections (pixel section, vertical selection circuit, column circuits, column memories, horizontal selection circuit, and output circuit) across two substrates within a single integrated device structure. This merging approach maintains device functionality while distributing heat generation, and the complexity is managed through a coordinated fabrication process that forms connection portions between substrates.
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 prevents cost increases from enlarged chip areas, maintains pixel section performance, and reduces dark current non-uniformity within the image pickup device.
Implementation Method 1
pixel section including photoelectric conversion elements each configured to generate electric charges by photoelectric conversion
Data Source
AI summary
An image pickup device which suppresses an increase in chip area of peripheral circuits without degrading the performance of a pixel section and makes it possible to prevent costs from being increased. The image pickup device includes a first semiconductor substrate and a second semiconductor substrate. A pixel section includes photo diodes each for generate electric charges by photoelectric conversion, floating diffusions each for temporarily storing the electric charges generated by the photo diode, and amplifiers each connected to the floating diffusion, for outputting a signal dependent on a potential of the associated floating diffusion. Column circuits are connected to vertical signal lines, respectively, for performing predetermined processing on signals output from the pixel section to vertical signal lines.