Solid-State Imaging Device Well Separation Structure
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Solution Overview
Problem
Existing solid-state imaging devices face challenges in efficiently separating wells when the photoelectric conversion unit and peripheral circuit or pixel circuit are formed on separate substrates, leading to reduced light receiving area and unsatisfactory well separation structures.
Innovation Solution
A separation structure where the well of a first conductivity type, with source and drain regions of the transistor amplifier, is separated from adjacent wells of the same conductivity type, allowing for efficient separation on separate substrates without reducing the light receiving area of the photoelectric conversion unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the photoelectric conversion unit and pixel circuit are disposed monolithically on the first substrate, then the device structure is simplified, but an extra space is needed to separate the wells, thus reducing a light receiving area of the photoelectric conversion unit
Solution Approach 1:
The pixel circuit is segmented from the photoelectric conversion unit and disposed on a separate second substrate. This segmentation eliminates the need for well separation within the first substrate, thereby maximizing the light receiving area while maintaining functional integration through substrate stacking
Solution Approach 2:
The pixel circuit is moved from the same plane (2D layout) to a different substrate layer (3D stacking). By utilizing the vertical dimension through separate substrates, the patent resolves the space conflict between photoelectric conversion units and pixel circuits, allowing full utilization of the first substrate for light reception
2Area of moving object
If the photoelectric conversion unit and peripheral circuit unit are separately formed on separate substrates, then the light receiving area is maximized, but a preferable separation structure of the wells is not sufficiently achieved
Solution Approach 1:
The well separation function is segmented and relocated to the second substrate where the pixel circuit is disposed. The separation structure includes a first separation structure between adjacent first wells and a second separation structure between adjacent second wells, achieving proper well isolation without compromising the first substrate's light receiving area
Solution Approach 2:
The second substrate acts as an intermediary carrier for the pixel circuit and well separation structures. By placing the separation mechanisms on this intermediate substrate, the patent achieves effective well separation while keeping the first substrate dedicated to photoelectric conversion with maximum light receiving area
3Reliability
If the wells are separated for each pixel to suppress charge leakage, then the signal quality is improved, but the device area increases and light receiving area is reduced
Solution Approach 1:
The well separation is implemented through segmented structures on the second substrate, including first separation structures between adjacent first wells and second separation structures between adjacent second wells. This segmentation achieves charge leakage suppression without expanding the first substrate area, as the separation mechanisms are distributed on the separate second substrate
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 separation structure improves the gain of the amplification transistor, suppresses cross-talk, and reduces floating diffusion capacitance, enhancing the performance of the solid-state imaging device.
Implementation Method 1
a photoelectric conversion unit and a transistor amplifier configured to amplify a signal generated by the photoelectric conversion unit
Data Source
AI summary
A purpose of the present invention is to provide a preferable separation structure of wells when a photoelectric conversion unit and a part of a peripheral circuit unit or a pixel circuit are separately formed on separate substrates and electrically connected to each other. To this end, a solid-state imaging device includes a plurality of pixels including a photoelectric conversion unit and a amplification transistor configured to amplify a signal generated by the photoelectric conversion unit; a first substrate on which a plurality of the photoelectric conversion units are disposed; and a second substrate on which a plurality of the amplification transistors are disposed. A well of a first conductivity type provided with a source region and a drain region of the amplification transistor is separated from a well, which is disposed adjacent to the well in at least one direction, of the first conductivity type provided with the source region and the drain region of the amplification transistor.