Solid-State Imaging Device Stacked Substrate Noise Reduction
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Solution Overview
Problem
Existing CMOS type solid-state imaging devices face challenges in achieving simultaneous exposure and readout of signal charges across all pixels without noise deterioration, particularly due to leakage currents and optical charges during signal retention, which affect image quality and chip area efficiency.
Innovation Solution
The implementation of a solid-state imaging device with two substrates, where the photoelectric conversion units are on one substrate and amplification and signal accumulation circuits are on another, utilizing a differential amplification circuit, feedback switch, and noise reduction circuit to manage signal amplification and noise reduction, allowing for simultaneous exposure and improved signal retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all pixels are simultaneously exposed and signal charges are simultaneously transmitted to accumulation capacitor units, then global shutter function is achieved, but chip area increases and noise is introduced during signal retention
Solution Approach 1:
The pixel circuit is divided into two separate substrates: the first substrate contains only the photoelectric conversion unit, while the second substrate contains the amplification circuit and accumulation capacitor unit. This segmentation allows each substrate to be optimized independently and reduces the overall chip area required for the complete pixel circuit.
Solution Approach 2:
The patent transitions from a planar integration approach to a three-dimensional stacked architecture by bonding two substrates together. The first substrate is positioned below the second substrate, creating vertical integration that reduces the lateral chip area while maintaining all necessary circuit functions.
2Ease of operation
If signal charges are retained in accumulation capacitor units for sequential reading, then reading flexibility is improved, but noise is introduced and signal quality deteriorates
Solution Approach 1:
The accumulation capacitor unit is extracted from the first substrate and placed on the second substrate. This separation allows the photoelectric conversion unit to be isolated from the amplification and accumulation circuits, reducing noise coupling and improving signal quality during retention.
Solution Approach 2:
A substrate bonding interface acts as an intermediary between the first and second substrates, providing controlled electrical connection while physically separating the photoelectric conversion unit from the noise-generating amplification and accumulation circuits.
3Ease of manufacture
If photoelectric conversion units and circuit components are integrated on a single substrate, then manufacturing is simplified, but chip area increases and signal retention noise increases
Solution Approach 1:
The pixel circuit is segmented across two separate substrates: the first substrate contains only the photoelectric conversion unit, while the second substrate contains the amplification circuit and accumulation capacitor unit. This segmentation isolates the photoelectric conversion unit from noise-generating circuits, reducing signal retention noise.
Solution Approach 2:
The patent replaces traditional planar integration with a substrate bonding approach, where two substrates are bonded together to form a three-dimensional structure. This substitution enables better electrical isolation and noise reduction while maintaining manufacturing feasibility through established semiconductor bonding techniques.
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 efficient signal amplification and noise reduction, improving image quality by reducing noise interference and allowing for a more compact chip design with enhanced sensitivity and global shutter functionality.
Implementation Method 1
a photoelectric conversion unit that is arranged in the first substrate
Data Source
AI summary
In a solid-state imaging device, an amplification transistor amplifies a signal generated by a photoelectric conversion unit and outputs the amplified signal. An analog memory accumulates the amplified signal output from the amplification transistor. A select transistor electrically connects the analog memory to a vertical signal line and selects any one of a first state in which the amplified signal accumulated in the analog memory is output to the vertical signal line and a second state in which the analog memory is electrically disconnected from the vertical signal line. A differential amplification circuit includes a first input terminal connected to a reference voltage and a second input terminal connected to the vertical signal line.