Organic Image Sensor Electrode Layout for Film Stress Control
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Solution Overview
Problem
Solid state image sensors face challenges with dark current and property fluctuations in organic photoelectric conversion films, particularly due to film stress issues during the manufacturing process, which affect sensitivity and image quality.
Innovation Solution
A solid state image sensor design that includes an organic photoelectric conversion film laminated on a semiconductor substrate with a lower electrode and a first upper electrode whose ends conform with the film, along with a film stress suppressor, such as a second upper electrode, to manage film stress and prevent property fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pixel size is reduced to increase the number of pixels, then the sensitivity of pixels decreases, which results in a decreased S/N ratio
Solution Approach 1:
The patent transitions from a planar 2D pixel arrangement to a 3D stacked architecture with multiple photoelectric conversion layers (first, second, and third layers) positioned at different depths. This vertical stacking enables more pixels to be packed within the same footprint while each pixel maintains adequate photoelectric conversion volume, thereby increasing pixel density without sacrificing sensitivity or S/N ratio
2Adaptability or versatility
If a primary color filter arrangement (e.g., Bayer) is used for color imaging, then green and blue colors are blocked from red pixels, resulting in sensitivity loss and false color generation
Solution Approach 1:
The patent employs a stacked 3D architecture where different photoelectric conversion layers are positioned at varying depths to capture different wavelengths. The first photoelectric conversion layer captures blue light, the second layer captures green light, and the third layer captures red light. This vertical spectral separation eliminates the need for lateral color filter arrangements, allowing each pixel to directly detect its designated wavelength without blocking other colors, thereby maintaining full sensitivity and eliminating false color artifacts
Solution Approach 2:
Each photoelectric conversion layer is optimized with specific properties tailored to its designated wavelength range. The first layer is optimized for blue light detection, the second for green, and the third for red. This localized optimization of photoelectric conversion characteristics at different depths enables wavelength-specific detection without interfering with other color channels, resolving the contradiction between color imaging capability and sensitivity
3Ease of manufacture
If the ends of the upper electrode are conform with the ends of the organic photoelectric conversion film, then film stress is locally concentrated during heat treatment, causing dark current and white flaw property fluctuations
Solution Approach 1:
The patent deliberately creates an asymmetric relationship between the upper electrode and the organic photoelectric conversion film. The upper electrode extends beyond the film boundaries on at least one side, breaking the conformal alignment. This asymmetric design prevents stress concentration at the film edges during heat treatment, as the stress is distributed over a larger area of the electrode rather than being localized at sharp corners where the film and electrode meet. Consequently, dark current and white flaw property fluctuations are suppressed while maintaining manufacturing simplicity
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 design effectively suppresses dark current and white flaws in the organic photoelectric conversion film, enhancing sensitivity and image quality by uniformly distributing film stress and preventing light loss, thus improving photoelectric conversion efficiency.
Implementation Method 1
an organic photoelectric conversion film which is laminated on the semiconductor substrate via the insulation film and formed at the regions where the plurality of pixels are formed
Data Source
AI summary
A solid state image sensor includes a semiconductor substrate where photoelectric conversion regions for converting light into charges are arranged per pixel planarly arranged; an organic photoelectric conversion film laminated at a light irradiated side of the semiconductor substrate via an insulation film and formed at the regions where the pixels are formed; a lower electrode formed at and in contact with the organic photoelectric conversion film at a semiconductor substrate side; a first upper electrode laminated at a light irradiated side of the organic photoelectric conversion film and formed such that ends of the first upper electrode are substantially conform with ends of the organic photoelectric conversion film when the solid state image sensor is planarly viewed; and a film stress suppressor for suppressing an effect of a film stress on the organic photoelectric conversion film, the film stress being generated on the first upper electrode.