Solid-State Image Sensor Depth-Stacked Light Receiving Sections
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Solution Overview
Problem
Conventional solid-state image capturing apparatuses face issues with low light utilization efficiency, sensitivity, and resolution due to the need for color filters, high concentration diffusion layers, and readout gate electrodes, which limit pixel size and image quality, especially in low-voltage applications and when trying to detect multiple colors simultaneously.
Innovation Solution
A solid-state image capturing apparatus with light receiving sections laminated in a depth direction of a semiconductor substrate, where trench sections reach to non-overlapping light receiving sections, allowing independent readout of signal charges using readout gate electrodes embedded in trenches, eliminating the need for color filters and high concentration diffusion layers, and enabling low-voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color filters are arranged in a mosaic on light receiving sections, then color signals can be detected, but light utilization efficiency and sensitivity decrease because about 2/3 of incident light is absorbed by color filters
Solution Approach 1:
The patent transitions from a two-dimensional mosaic arrangement of color filters on the surface to a three-dimensional stacked arrangement of light receiving sections in the depth direction. This allows different wavelength bands to be detected at different depths without requiring color filters, thereby improving light utilization efficiency while maintaining color detection capability.
Solution Approach 2:
The patent removes color filters from the optical path and replaces them with wavelength-selective light receiving sections positioned at different depths. This extraction of the color filtering function from the surface level and its integration into the depth-direction structure eliminates light absorption losses while preserving color signal detection.
2Reliability
If high concentration diffusion layers are used to transfer signal charges, then charge transfer is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent replaces the conventional high concentration diffusion layer charge transfer mechanism with an electric field-based transfer mechanism using readout gate electrodes. This substitution reduces structural complexity while maintaining or improving charge transfer efficiency through controlled electric fields in trench sections.
Solution Approach 2:
The patent introduces readout gate electrodes as intermediary elements that mediate charge transfer between light receiving sections and readout circuits. These electrodes provide controlled charge transfer paths without requiring high concentration diffusion layers, thereby simplifying the overall device structure.
3Ease of operation
If readout gate electrodes are provided on the substrate surface, then signal charge readout is enabled, but the size of light receiving regions must be reduced, leading to decreased light receiving sensitivity
Solution Approach 1:
The patent moves readout gate electrodes from the substrate surface to the depth direction, positioning them adjacent to light receiving sections at their respective depths. This three-dimensional arrangement allows large surface-area light receiving regions to maintain full sensitivity while enabling efficient charge transfer through vertically positioned electrodes.
Solution Approach 2:
The patent segments the readout function into multiple depth-level gate electrodes, each adjacent to specific light receiving sections. This segmentation allows independent optimization of light receiving area and charge transfer paths, preventing the trade-off between readout capability and light receiving sensitivity.
4Measurement precision
If multiple color signals are detected at different pixel sections, then color information is obtained, but resolution decreases because other color data must be obtained by computation from different locations
Solution Approach 1:
The patent arranges light receiving sections detecting different wavelength bands in the depth direction at the same horizontal position (same pixel section). This three-dimensional configuration enables simultaneous detection of multiple color signals at each pixel location, eliminating the need for computational reconstruction and preserving full image resolution.
Solution Approach 2:
The patent merges multiple color detection functions into a single pixel section by stacking light receiving sections at different depths. This consolidation allows all color information to be obtained at each pixel location simultaneously, eliminating the need for computational merging from different pixel sections and maintaining high resolution.
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 design enhances light receiving sensitivity and resolution, allows for independent color signal readout, reduces power consumption, and eliminates the need for color filters, resulting in improved image quality and manufacturing efficiency.
Implementation Method 1
a plurality of light receiving sections (a plurality of pixel sections) are arranged in two dimensions and in a matrix and in a depth direction in a semiconductor substrate and perform a photoelectric conversion on incident light so as to generate a signal charge
Implementation Method 2
of electromagnetic waves of incident subject light, electromagnetic waves having wavelength bands corresponding to depths of the respective light receiving sections are detected at the respective light receiving sections in accordance with wavelength dependency of optical absorption coefficient of a semiconductor substrate material of the semiconductor substrate
Data Source
AI summary
An image capturing apparatus has a plurality of solid-state image capturing devices each having light receiving sections laminated in a depth direction of a semiconductor substrate. The devices are sequentially arranged in a direction along a substrate surface. Incident light waves having wavelength bands corresponding to depths of respective light receiving sections are detected there and generate signal charges. Bands are associated with light receiving sections by the wavelength dependence of the optical absorption. Trench sections each reach from a light incident surface or an opposite substrate surface to respective light receiving sections that do not overlap each other in a plane view. Electric charge transfer sections transfer electric charges independently from the light receiving sections via side wall portions of their respective trenches to the light incident surface side or the opposite substrate surface side at the time of driving readout gate electrodes at each trench section.