Solid-State Imaging Device Reset Transistor Voltage Control
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Solution Overview
Problem
Existing solid-state imaging devices face image quality reduction due to blooming, where overflowed charges from one pixel can flow into adjacent pixels, causing noise, and the reliability of the gate insulating film is compromised due to prolonged high electric fields.
Innovation Solution
A solid-state imaging device and method that involve a pixel structure with a photoelectric conversion element, a floating diffusion layer, transfer, reset, and amplifier transistors, along with a control unit that supplies specific voltages to the reset transistor to manage the potential of the floating diffusion layer, thereby reducing blooming and maintaining the reliability of the gate insulating film by controlling the electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the floating diffusion layer voltage is kept at a high level during the accumulation period to prevent blooming, then blooming suppression is improved, but the electric field between the transfer transistor gate and floating diffusion layer increases, reducing gate insulating film reliability
Solution Approach 1:
The patent applies dynamics by making the floating diffusion layer voltage variable rather than fixed. The voltage is dynamically adjusted based on the operational phase: during the accumulation period, a first voltage level is applied to suppress blooming, while during the transfer period, a second voltage level is applied to reduce the electric field stress on the gate insulating film. This temporal variation in voltage levels resolves the contradiction between blooming suppression and gate insulating film reliability.
Solution Approach 2:
The patent changes the voltage parameter of the floating diffusion layer according to different operational periods. By switching between a first voltage (during accumulation) and a second voltage (during transfer), the system optimizes performance for each phase: the first voltage prevents charge overflow to adjacent pixels, while the second voltage minimizes electric field stress on the gate insulating film, thereby resolving the technical contradiction.
2Reliability
If multiple voltage levels are applied to the reset transistor gate to control the floating diffusion layer potential, then blooming suppression and gate insulating film reliability are improved, but the control circuit complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the control circuit to automatically supply the appropriate voltage levels to the reset transistor gate based on the operational phase. The control circuit is designed in advance to provide a first voltage during the accumulation period and a second voltage during the transfer period, eliminating the need for complex real-time calculations or manual adjustments, thus improving reliability while keeping the control mechanism manageable.
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
The solution effectively suppresses image quality deterioration from blooming and maintains the endurance reliability of the gate insulating film by managing the electric field and potential of the floating diffusion layer, ensuring accurate signal transfer and improved image quality.
Implementation Method 1
a photoelectric conversion element
Data Source
AI summary
A solid-state imaging device includes a pixel including a photoelectric conversion element, a floating diffusion layer, a transfer transistor, a reset transistor, and an amplifier transistor, and a control unit configured to supply a first voltage to a gate of the reset transistor when the charges are accumulated in the photoelectric conversion element, the first voltage being set between a second voltage and a third voltage; subsequently supply the second voltage to the gate of the reset transistor when the reset transistor is turned on in order to reset the potential of the floating diffusion layer, and subsequently supply the third voltage to the gate of the reset transistor when the amplifier transistor outputs the signal based on the potential of the floating diffusion layer.