Solid-State Imaging Device Substrate Segmentation for Noise Reduction
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Solution Overview
Problem
CMOS-type solid-state imaging devices with global shutter function face challenges in maintaining signal quality due to noise caused by light during the waiting period until signal charges are read, leading to potential distortion in images, especially when capturing fast-moving subjects.
Innovation Solution
The solution involves electrically connecting two substrates via a connector, where photoelectric conversion elements are on one substrate and read circuits and signal processing circuits are distributed between the substrates, allowing for simultaneous exposure and storage of signal charges, and subsequent amplification and processing to minimize noise and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal charges are stored in storage capacitors during the waiting period until reading, then simultaneous exposure (global shutter function) is achieved, but noise caused by light during storage deteriorates signal quality
Solution Approach 1:
The pixel unit is divided into two separate substrates: the first substrate contains photoelectric conversion units and storage capacitors, while the second substrate contains read circuits. This segmentation allows signal charges to be stored in shielded storage capacitors on the first substrate, isolating them from light-induced noise, while read circuits on the second substrate process the signals without interfering with the storage process.
Solution Approach 2:
Connection electrodes serve as intermediaries to electrically connect the first substrate (containing photoelectric conversion units and storage capacitors) and the second substrate (containing read circuits). These connection electrodes transmit signal charges from the storage capacitors to the read circuits without exposing the stored charges to light, thereby preventing noise contamination while enabling signal readout.
2Area of stationary object
If all circuits are integrated on one substrate, then device complexity is reduced, but chip area increases due to light-shielding requirements for storage capacitors
Solution Approach 1:
The device is segmented into two substrates with distinct functional assignments. The first substrate is dedicated to photoelectric conversion and charge storage, while the second substrate handles signal reading and processing. This segmentation eliminates the need for light-shielding structures over the entire chip area, as only the storage capacitor regions on the first substrate require shielding, thereby reducing the overall light-shielding layer area.
Solution Approach 2:
The invention transitions from a planar integration approach to a three-dimensional stacked architecture. By stacking two substrates vertically and connecting them through connection electrodes, the device achieves functional integration without requiring all circuits to occupy the same two-dimensional plane. This vertical arrangement reduces the area required for light-shielding structures while maintaining electrical connectivity between all components.
3Ease of manufacture
If read circuits are placed on the same substrate as photoelectric conversion units, then manufacturing is simplified, but signal charges are exposed to light during the waiting period causing noise
Solution Approach 1:
The device is divided into two functionally distinct substrates: the first substrate contains photoelectric conversion units and storage capacitors, while the second substrate contains read circuits. This segmentation physically separates the charge storage function from the signal reading function, ensuring that stored signal charges remain isolated from light exposure during the waiting period while still allowing for streamlined manufacturing through separate substrate fabrication followed by bonding.
Solution Approach 2:
Connection electrodes act as intermediaries that electrically link the first substrate (with photoelectric conversion units and storage capacitors) and the second substrate (with read circuits). These connection electrodes enable signal charge transfer from storage to readout without requiring direct co-location of all circuits on one substrate, thereby preventing light-induced noise while maintaining manufacturing efficiency through a modular fabrication and bonding process.
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 reduces the chip area and prevents signal quality deterioration, enabling high-quality image capture with reduced noise and distortion, particularly when imaging fast-moving subjects.
Implementation Method 1
signal charges generated and stored by photoelectric conversion units serving as light-receiving units of pixels
Data Source
AI summary
In the solid-state imaging device, first and second substrates are electrically connected to each other via connectors electrically connecting the first and second substrates. A photoelectric conversion element is disposed in the first substrate. A read circuit is disposed in the second substrate and reads a signal generated by the photoelectric conversion element and transmitted via the connector. In a signal processing circuit including elements or circuits performing signal processing on the read signal, some of the elements or circuits are disposed in the first substrate, the remaining elements or circuits are disposed in the second substrate, and the elements or circuits disposed in the first and second substrates are electrically connected to each other via the connector.