Stacked Solid-State Imager Shielding for Floating Diffusion PLS
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Solution Overview
Problem
Conventional solid-state imaging devices face issues with parasitic light sensitivity (PLS) due to stray light entering the floating diffusion, leading to erroneous signal charge detection.
Innovation Solution
A solid-state imaging device design that includes a first semiconductor substrate with photoelectric conversion units and a second semiconductor substrate with a charge holding unit, where the second wiring layer is positioned between the first and second semiconductor layers, and a light shielding layer is provided to block stray light from reaching the charge holding unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the floating diffusion is separated from the optical center of the pixel to inhibit stray light, then parasitic light sensitivity is reduced, but the structural complexity and device design difficulty increase
Solution Approach 1:
A light shielding layer is introduced as an intermediary component between the photoelectric conversion unit and the floating diffusion. This layer selectively blocks stray light paths while allowing the device structure to remain conventional, thus reducing parasitic light sensitivity without increasing structural complexity
Solution Approach 2:
The solution moves from modifying the horizontal position of the floating diffusion to adding a vertical layer (light shielding layer) in the thickness direction of the device. This dimensional change allows stray light blocking without altering the planar layout or increasing lateral structural complexity
2Object-affected harmful factors
If a light shielding layer is added to block stray light from the charge holding unit, then parasitic light sensitivity is suppressed, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The light shielding layer is designed to serve multiple functions: it blocks stray light from reaching the charge holding unit, and can be integrated with existing device layers. This multi-functionality reduces the need for additional dedicated components, simplifying manufacturing
Solution Approach 2:
The light shielding layer is merged with existing device structures such as wiring layers or insulating layers, rather than being implemented as a separate standalone component. This integration approach reduces manufacturing steps and maintains ease of production
3Object-affected harmful factors
If the second wiring layer is positioned between the first and second semiconductor layers, then light shielding effectiveness is improved, but the device structure becomes more complex
Solution Approach 1:
The second wiring layer is designed to simultaneously serve as both an electrical connection element and a light shielding element. By making the wiring layer perform dual functions, no additional light shielding structure is needed, thus maintaining structural simplicity while achieving effective stray light blocking
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 effectively suppresses parasitic light sensitivity by blocking stray light, enhancing the accuracy of signal charge detection and reducing photoelectric conversion in the charge holding unit.
Implementation Method 1
a light shielding layer provided in at least one of the first wiring layer or the second wiring layer at a position facing the charge holding unit in a thickness direction
Implementation Method 2
a first semiconductor layer including a first region including a first semiconductor material and a second region including a second semiconductor material... and including a photoelectric conversion unit that performs photoelectric conversion
Data Source
AI summary
PLS is further suppressed. A solid-state imaging device includes: a first semiconductor substrate including a first semiconductor layer provided with a plurality of photoelectric conversion units that performs photoelectric conversion, and a first wiring layer provided on a surface side opposite to a light incident surface of the first semiconductor layer; a second semiconductor substrate including a second semiconductor layer provided with a charge holding unit that holds signal charge generated in the photoelectric conversion unit and a second wiring layer provided on one surface side of the second semiconductor layer, and overlapped with and bonded to the first semiconductor substrate such that the second wiring layer is positioned between the first wiring layer and the second semiconductor layer; and a light shielding layer provided in at least one of the first wiring layer or the second wiring layer at a position facing the charge holding unit in a thickness direction.