Island-Shaped Semiconductor Structure for Solid-State Imaging Device Light Collection
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Solution Overview
Problem
Conventional CMOS image sensors have a limited ratio of surface area of the light-receiving section (photodiode) to the overall surface area of one pixel, making it difficult to increase this ratio effectively.
Innovation Solution
A solid-state imaging device with an island-shaped semiconductor structure, where a transparent conductive film is used for the pixel selection line and a part of the gate is disposed inside a depression in the sidewall of the semiconductor layer, allowing for a larger light-receiving section area relative to the overall pixel area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional planar pixel structure with photodiode and three MOS transistors is used, then the device can perform photoelectric conversion and signal amplification, but the ratio of light-receiving section area to overall pixel area is limited to around 30%
Solution Approach 1:
The patent transitions from a planar two-dimensional layout to a three-dimensional vertical structure by stacking the photodiode, charge storage section, and transistor components in multiple layers. This vertical integration allows the light-receiving section to occupy a larger proportion of the pixel area while maintaining compact overall dimensions, effectively increasing the light-receiving area ratio beyond the conventional 30% limit.
Solution Approach 2:
The patent implements a nested structure where the charge storage section is positioned between the photodiode and the transistor, with each component vertically stacked and interconnected. This nesting arrangement allows multiple functional elements to occupy overlapping spatial footprints in the vertical dimension, maximizing the light-receiving area while accommodating all necessary circuit components within a compact pixel footprint.
2Use of energy by moving object
If the light-receiving section area is increased to improve light collection efficiency, then more light can be captured, but the area available for other pixel components (transistors, wiring) is reduced
Solution Approach 1:
By moving components into the vertical dimension through stacking, the patent resolves the spatial conflict between light-receiving area and component accommodation. The photodiode can be enlarged in the horizontal plane to improve light collection, while transistors and charge storage sections are positioned in upper layers, eliminating the need to compromise light-receiving area for component space.
Solution Approach 2:
The patent segments the pixel structure into distinct functional layers: the photodiode layer for light reception, the charge storage section for charge accumulation, and the transistor layer for signal processing. This segmentation allows each component to be optimized independently for its specific function while maintaining efficient interconnections through vertical pathways, reducing overall structural complexity despite the three-dimensional configuration.
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 configuration significantly increases the ratio of the surface area of the light-receiving section to the overall surface area of one pixel, enhancing the image sensor's light collection efficiency.
Implementation Method 1
a charge storage section comprised of a third semiconductor layer connected to the second semiconductor layer and adapted, in response to receiving light, to undergo a change in amount of electric charges therein
Data Source
AI summary
It is an object to provide an image sensor having a sufficiently-large ratio of a surface area of a light-receiving section to an overall surface area of one pixel. This object is achieved by a solid-state imaging device comprising: a signal line formed on a substrate; an island-shaped semiconductor arranged on the signal line; and a pixel selection line connected to a top of the island-shaped semiconductor, wherein the island-shaped semiconductor includes: a first semiconductor layer formed as a bottom portion of the island-shaped semiconductor and connected to the signal line; a second semiconductor layer formed above and adjacent to the first semiconductor layer; a gate connected to the second semiconductor layer through a dielectric film; a charge storage section comprised of a third semiconductor layer connected to the second semiconductor layer and adapted, in response to receiving light, to undergo a change in amount of electric charges therein; and a fourth semiconductor layer formed above and adjacent to the second and third semiconductor layers, and wherein the pixel selection line is comprised of a transparent conductive film, and a part of the gate is disposed inside a depression formed in a sidewall of the second semiconductor layer.