Imaging Device Pixel Row Voltage Reversal

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Solution Overview

Problem

The reliability of solid-state imaging devices deteriorates due to increased electric-charge traps in the photoelectric conversion film, caused by a constant electric field applied during exposure periods, leading to variations in photoelectric conversion characteristics.

Innovation Solution

A driving method and device configuration where an electric potential opposite to that applied during exposure is applied to the photoelectric conversion film at predetermined timings outside the exposure period, specifically using a driving section to vary the electric potential on pixel rows with different read timings, thereby reducing electric-charge traps and maintaining uniform voltage bias across pixels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a constant electric field is applied to the photoelectric conversion film during exposure periods, then the photoelectric conversion process can be maintained, but electric-charge traps accumulate in the film leading to reliability deterioration

Engineering Contradiction:

Improvephotoelectric conversion characteristic stabilityVSAvoidelectric-charge traps accumulation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies periodic reversal of the electric field direction by switching the polarity of the voltage applied to the pixel electrode between exposure periods. This periodic action prevents permanent accumulation of electric-charge traps in the photoelectric conversion film while maintaining effective photoelectric conversion during exposure, thereby resolving the contradiction between maintaining conversion stability and preventing trap accumulation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent inverts the electric field direction by reversing the voltage polarity on the pixel electrode between exposure periods. This inversion causes previously accumulated positive charges to be repelled and previously accumulated negative charges to be attracted, effectively clearing trapped charges and preventing their permanent accumulation, thus resolving the harmful effect while preserving the beneficial photoelectric conversion function.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of operation

If pixel electrodes are separated for individual pixels, then each pixel can be independently controlled, but manufacturing complexity increases

Engineering Contradiction:

Improveindependent pixel controlVSAvoidpixel electrode fabrication

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The patent divides the pixel array into multiple independently controllable pixel electrodes, each capable of receiving separate voltage signals. This segmentation enables independent control of each pixel's exposure timing and electric field reversal, providing operational flexibility while maintaining a manageable manufacturing process through standard photolithographic patterning techniques.

Inventive Principle:

Principle #1Segmentation

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 effectively reduces the accumulation of electric-charge traps in the photoelectric conversion film, enhancing the reliability and consistency of the imaging device by preventing characteristic variations across pixels.

Implementation Method 1

a photoelectric conversion film formed on the pixel electrode

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 2

an electric field having a fixed direction is applied to the photoelectric conversion film sandwiched by the pixel electrodes laid out on the lower surface of the film and the common opposite electrode provided on the upper surface of the film

Methodology Applied

Scientific EffectElectric field: Electric Field

Data Source

PatentUS9531971B2Imaging device, driving method and electronic apparatus with electric potential applied outside exposure period

Publication Date: 2016.12.27 SONY SEMICON SOLUTIONS CORP

AI summary

Disclosed herein is an imaging device including: a plurality of pixels disposed to form a matrix having pixel rows, the pixels including a pixel electrode formed on a silicon substrate for one of the pixels by being separated away from another pixel electrodes formed for one of the other pixels, a photoelectric conversion film formed on the pixel electrode, and an opposite electrode formed on the photoelectric conversion film; and a driving section configured to apply an electric potential to the photoelectric conversion film on each of the pixel rows at least having read timings different from each other with a predetermined timing outside an exposure period of the pixels in a direction opposite to that of an electric potential applied to the photoelectric conversion film during the exposure period of the pixels.