Solid State Imaging Pixel Connecting Portential Equalization
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Solution Overview
Problem
In solid state imaging devices, charges accumulating in the connecting portion between the photoelectric converting element and the semiconductor substrate lead to lag and non-linear signal output characteristics due to thermal diffusion, making it difficult to achieve perfect reset noise removal and linearity correction.
Innovation Solution
The imaging device sets the connecting portion and potential barrier portion to the same potential by injecting charges, using a driving unit that controls the reset transistor and charge injection transistor to manage potential differences, thereby preventing charge accumulation and ensuring linear signal output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charges are allowed to accumulate in the connecting portion during exposure, then signal output is generated, but lag occurs and linearity is degraded due to thermal diffusion
Solution Approach 1:
The patent applies equipotentiality by setting the potential of the connecting portion equal to the potential of the pixel electrode through charge injection. This eliminates potential differences that cause thermal diffusion of charges, thereby preventing lag and maintaining signal linearity while enabling accurate reset noise removal.
Solution Approach 2:
The patent implements preliminary action by injecting charges into the connecting portion before the exposure period begins. This preliminary charge injection establishes the correct potential relationship (connecting portion potential = pixel electrode potential) in advance, preventing thermal diffusion during exposure and ensuring both linearity and reset noise removal accuracy.
2Measurement precision
If charge injection is performed to equalize potentials, then lag is prevented and linearity is improved, but additional control complexity is introduced
Solution Approach 1:
The patent achieves multi-functionality by utilizing the existing reset transistor for dual purposes: its conventional reset function and the additional function of injecting charges to equalize potentials. This approach improves signal linearity without requiring separate dedicated charge injection circuitry, thereby minimizing additional control complexity.
3Reliability
If reset operation is performed to discharge accumulated charges, then reset noise is generated, but perfect reset noise removal requires complex CDS processing
Solution Approach 1:
The patent applies preliminary action by equalizing the potential of the connecting portion with the pixel electrode potential before charge accumulation begins. This prevents thermal diffusion and lag at the source, thereby improving reset noise removal accuracy and reducing the complexity of subsequent CDS processing requirements.
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 lag and allows for accurate linearity correction of signal output characteristics, improving the sensitivity and linearity of the imaging device by maintaining equal potentials across the connecting and potential barrier portions.
Implementation Method 1
a photoelectric converting layer put between the electrodes, respectively
Implementation Method 2
a potential barrier portion that is arranged adjacent to the connecting portion in the semiconductor substrate and that acts as a potential barrier against a potential of the connecting portion
Data Source
AI summary
An imaging device includes a solid state imaging element that includes a plurality of pixels; and a driving unit; wherein each pixel includes: a photoelectric converting element includes a pair of electrodes stacked above a semiconductor substrate and a photoelectric converting layer arranged between the electrodes; a connecting portion that is arranged in the semiconductor substrate; a potential barrier portion; a first charge accumulating portion; and a signal output circuit, and wherein the driving unit drives the solid state imaging element so that the connecting portion and the potential barrier portion are set to a same potential by injecting charges into the connecting portion.