Solid-State Image Pickup Element Read Channel Stacking
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Solution Overview
Problem
Conventional solid-state image pickup devices have a limited increase in the ratio of the surface area of the light-receiving section (photodiode) to the overall surface area of one pixel due to the formation of photodiode, read channel, and n-type CCD channel region in the same plane.
Innovation Solution
A solid-state image pickup element with a read channel arranged in a non-horizontal direction, featuring a second-conductive type planar semiconductor layer, a first-conductive type high-concentration impurity region, and a second-conductive type CCD channel region, allowing for a reduced occupancy area of the read channel and increased surface area of the light-receiving section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the read channel, photodiode, and n-type CCD channel region are formed in the same plane, then the device structure is simple and easy to manufacture, but the ratio of the surface area of the light-receiving section to the overall surface area of one pixel is limited
Solution Approach 1:
The patent transitions from a planar two-dimensional arrangement to a three-dimensional stacked structure. The photodiode is formed in the first-conductive type planar semiconductor layer, while the read channel and n-type CCD channel region are formed in the second-conductive type planar semiconductor layer beneath it. This vertical stacking in the third dimension allows the light-receiving section area to be increased without proportionally increasing the pixel area, as the read channel components are positioned underneath rather than alongside the photodiode.
2Area of moving object
If the read channel area is reduced to increase the light-receiving section area ratio, then the light-receiving capability is improved, but the read channel may become too small to effectively read signal charges
Solution Approach 1:
By moving the read channel components to a lower layer (second-conductive type planar semiconductor layer) beneath the photodiode layer, the patent decouples the area requirements of the light-receiving section and the read channel. The read channel can maintain sufficient cross-sectional area for effective charge reading in the vertical dimension, while the photodiode achieves maximum surface area in the horizontal plane without being constrained by read channel space requirements.
Solution Approach 2:
The patent divides the semiconductor structure into distinct functional layers: the first-conductive type planar semiconductor layer contains the photodiode for light reception, while the second-conductive type planar semiconductor layer contains the read channel and n-type CCD channel region for charge reading. This segmentation into separate layers allows each component to be optimized for its specific function without compromising the other, ensuring both large light-receiving area and reliable signal charge reading capability.
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 drastically reduces the occupancy area of the read channel, enhancing the ratio of the surface area of the light-receiving section to the overall surface area of one pixel, thereby improving the device's light-receiving capability.
Implementation Method 1
a second-conductive type photoelectric conversion region formed in a portion of the first-conductive type planar semiconductor layer located beneath the first-conductive type high-concentration impurity region and in a part of a lower region of the remaining part of the sidewall of the hole portion of the first-conductive type planar semiconductor layer, and adapted to undergo a change in charge amount upon receiving light
Data Source
AI summary
A method of producing a solid-state image pickup element includes forming a hole portion, forming a first-conductive type high-concentration impurity region in a bottom wall of the hole portion, and forming a first-conductive type high-concentration impurity-doped element isolation region in a part of a sidewall of the hole portion and connected to the first-conductive type high-concentration impurity region. The method also includes forming a second-conductive type photoelectric conversion region beneath the first-conductive type high-concentration impurity region and adapted to undergo a change in charge amount upon receiving light, and forming a transfer electrode formed on the sidewall of the hole portion through a gate dielectric film. The method further includes forming a second-conductive type CCD channel region in a top surface of the first-conductive type planar semiconductor layer, and forming a read channel sandwiched between the second-conductive type photoelectric conversion region and the second-conductive type CCD channel region.