Imaging Element Recess Layout for Long-Wavelength Pixel Scaling
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Solution Overview
Problem
There is a challenge in creating an imaging element that can efficiently absorb long-wavelength light without increasing the thickness of the Si layer, while also reducing pixel size and maintaining high sensitivity.
Innovation Solution
The imaging element incorporates a recessed portion region on the light-receiving surface with non-intersecting recessed portions, which increases the optical path length of incident light and enhances absorption of long-wavelength light, such as near-infrared, without increasing the silicon layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the Si layer is increased to improve sensitivity to long-wavelength light, then light absorption efficiency improves, but pixel size cannot be reduced and device complexity increases
Solution Approach 1:
The patent transitions from increasing thickness in the vertical dimension to creating optical path extensions through lateral dimensioning using recessed portions. The recessed portions extend the optical path length horizontally across the silicon surface, allowing enhanced light absorption without increasing vertical thickness or pixel volume.
Solution Approach 2:
The patent employs curved or inclined surfaces within the recessed portions rather than flat surfaces. These curved surfaces increase the optical path length by causing light to traverse a longer, non-linear path through the silicon material, thereby improving absorption efficiency without requiring increased thickness.
2Reliability
If irregular structures are added to diffract light and improve long-wavelength absorption, then light absorption efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The patent divides the light-receiving surface into multiple discrete recessed portions rather than creating a continuous complex irregular structure. Each recessed portion is a separate, simplified geometric feature that can be independently formed, reducing manufacturing complexity while collectively providing the desired light diffraction and absorption enhancement.
3Productivity
If pixels are downsized to increase pixel count, then device integration improves, but light absorption efficiency decreases
Solution Approach 1:
The patent nests the recessed portions within the boundaries of each pixel structure. These recessed features are embedded in the pixel's light-receiving surface, allowing the pixel to maintain its compact size while containing internal structures that extend the optical path and enhance light absorption efficiency within the same footprint.
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 allows for efficient absorption of long-wavelength light, preventing dark current increase and maintaining uniform depth, thus facilitating the trade-off between saturated charge amount and transfer design.
Implementation Method 1
an imaging device that is provided with an irregular structure on a light receiving surface-side interface of a photoelectric conversion region of each of pixels arranged in a two-dimensional manner and efficiently absorbs light with a long wavelength by diffracting light by the irregular structure
Data Source
AI summary
The present technology relates to an imaging element and an electronic device that enable provision of an imaging element that enables pixels to be reduced in size without increasing a thickness of an Si layer and efficiently absorbs light with a long wavelength. Photoelectric conversion regions and a region including a plurality of recessed portions on a light-receiving surface side of the photoelectric conversion regions are included, and the recessed portions are in a shape with no intersecting parts in a plan view. The recessed portions are configured of first recessed portions having a linear shape in a first direction and second recessed portions having a linear shape in a second direction, the first recessed portions and the second recessed portions are provided in a shape with no intersecting parts. The present technology can be applied to an imaging element that receives light with a long wavelength, for example.