CMOS Imaging Element Capacitance Expansion for Higher Saturation Charge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors face challenges in achieving high light sensitivity while miniaturizing photodiodes, leading to degraded image quality due to reduced light-receiving areas, necessitating an increase in saturation signal electric charge amount to improve dynamic range and signal-to-noise ratio.
Innovation Solution
The imaging element incorporates a specific structure with a first P-type impurity region, a capacitance expanding portion forming a PN junction surface with a second P-type and first N-type impurity region, and the first N-type impurity region, sequentially layered from the surface side of a semiconductor substrate, to enhance signal electric charge accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the light-receiving area of the photodiode is reduced to miniaturize the imaging element, then the device size is reduced, but light sensitivity is degraded
Solution Approach 1:
The patent extends the light-receiving structure from two-dimensional surface to three-dimensional depth by forming the light-receiving portion that penetrates through the semiconductor substrate. This vertical extension increases the effective light-receiving area without increasing the planar footprint, thereby maintaining miniaturization while improving light sensitivity
Solution Approach 2:
The patent embeds the light-receiving portion within the semiconductor substrate structure, nesting it between the first and second semiconductor substrates. The light-receiving portion is positioned to overlap with the lamination portion, creating a nested configuration that maximizes space utilization and light-receiving capability within the compact imaging element structure
2Volume of moving object
If the light-receiving area of the photodiode is reduced to miniaturize the imaging element, then the device size is reduced, but image quality is degraded
Solution Approach 1:
By extending the light-receiving structure vertically through the substrate, the patent increases the effective light-receiving area without increasing planar dimensions. This three-dimensional approach maintains high-definition image quality by capturing more light while preserving the miniaturized form factor
Solution Approach 2:
The patent concentrates the light-receiving function in a specific localized region by forming the light-receiving portion that penetrates through the substrate at a predetermined position. This localized enhancement of light-receiving capability improves image quality in the critical light-receiving area without requiring overall enlargement of the imaging element
3Reliability
If the saturation signal electric charge amount is increased to improve dynamic range and SN ratio, then image sensor characteristics are improved, but the size of the imaging element increases
Solution Approach 1:
The patent increases the saturation signal electric charge amount by extending the light-receiving portion vertically through the substrate, utilizing the depth dimension rather than expanding planar area. This allows accumulation of more photoelectric charge without increasing the overall imaging element size
Solution Approach 2:
The light-receiving portion is nested within the semiconductor substrate structure, positioned to overlap with the lamination portion between substrates. This nested configuration enables increased charge accumulation capacity while maintaining the compact overall dimensions of the imaging element
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 increases the saturation signal electric charge amount, thereby improving the dynamic range and signal-to-noise ratio of the image sensor without increasing the size of the imaging element, maintaining miniaturization while enhancing light sensitivity.
Implementation Method 1
a pn junction capacitor of a photodiode (PD) that is a photo-electric conversion element
Data Source
AI summary
The present technology relates to an imaging element and an electronic apparatus capable of expanding a saturation signal electric charge amount. A first P-type impurity region, a capacitance expanding portion that forms a PN junction surface with a second P-type impurity region and a first N-type impurity region, and the first N-type impurity region are sequentially provided in a depth direction from a surface side where a wiring layer of a semiconductor substrate is laminated. The second P-type impurity region is formed in a stripe on a plane of the capacitance expanding portion that perpendicularly intersects with the depth direction. The stripe is formed, on the plane of the capacitance expanding portion that perpendicularly intersects with the depth direction, in a direction perpendicular to a side where an electrode that reads accumulated electric charge is formed. The present technology can be applied to an imaging element.