Solid-State Image Sensor Pixel Voltage Control for Leakage Uniformity
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Solution Overview
Problem
Variation in the voltage of the charge retention unit in solid-state imaging devices leads to leakage current variations among pixels, resulting in point defects and decreased imaging quality due to direct connection between the charge retention unit and the photoelectric conversion unit.
Innovation Solution
Incorporating a voltage control transistor to regulate the output end voltage of the output transistor, reducing voltage variation in the charge retention unit and improving imaging quality by controlling the voltage applied to the photoelectric conversion unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact portion directly connects the photoelectric conversion unit and the charge retention unit, then electrical connection is achieved, but leakage current is generated due to the buried PN junction
Solution Approach 1:
An intermediate n-type diffusion layer is introduced between the p-type semiconductor substrate and the photoelectric conversion unit. This intermediate layer acts as a mediator that eliminates the need for a buried PN junction, thereby preventing reverse bias leakage current while maintaining electrical connection between the photoelectric conversion unit and the charge retention unit.
2Object-generated harmful factors
If the voltage of the charge retention unit is lowered to reduce leakage current, then leakage current decreases, but voltage variation among pixels increases causing point defects
Solution Approach 1:
The charge retention unit is designed to maintain a constant potential across all pixels by using a shared reference potential structure. This equipotential design ensures that voltage variation among pixels is minimized, preventing point defects while allowing the overall voltage level to be optimized for leakage current reduction.
3Reliability
If a stacked solid-state imaging device with multiple photoelectric conversion regions is used, then sensitivity decreases due to light absorption are reduced, but device complexity increases
Solution Approach 1:
Instead of stacking multiple photoelectric conversion regions vertically (adding spatial complexity), the invention uses a planar arrangement with color filters in the vertical dimension. Light passes through color filters that selectively absorb wavelengths, and the photoelectric conversion occurs in a single layer, maintaining simplicity while achieving wavelength-specific sensitivity.
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 reduces voltage variation in the charge retention unit, minimizing leakage current and enhancing imaging quality by stabilizing the voltage applied to the photoelectric conversion unit, thereby improving the overall performance of the solid-state imaging device.
Implementation Method 1
a first photoelectric conversion unit that generates and accumulates signal charge by receiving light having entered the pixel and photoelectrically converting the light
Data Source
AI summary
The present technology relates to a solid-state imaging device that can improve imaging quality by reducing variation in the voltage of a charge retention unit, a method of driving the solid-state imaging device, and an electronic apparatus. A first photoelectric conversion unit generates and accumulates signal charge by receiving light that has entered a pixel, and photoelectrically converting the light. A first charge retention unit retains the generated signal charge. A first output transistor outputs the signal charge in the first charge retention unit as a pixel signal, when the pixel is selected by the first select transistor. A first voltage control transistor controls the voltage of the output end of the first output transistor. The present technology can be applied to pixels in solid-state imaging devices, for example.