Solid-State Imaging Device Substrate Segmentation for Noise Reduction
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Solution Overview
Problem
CMOS type solid-state imaging devices with global shutter functions face challenges in chip area increase and signal quality degradation due to the need for photoelectric conversion and memory elements to be on the same substrate, leading to noise issues from light leakage and dark current.
Innovation Solution
A solid-state imaging device is designed with a first substrate for photoelectric conversion elements and a second substrate for memory elements, bonded together with connecting portions, where the first substrate includes a light-blocking film to prevent light from reaching the memory elements, and the wiring layers are positioned to block transmitted light, allowing for separate control units to manage pixel signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoelectric conversion elements and memory elements are formed on the same substrate to achieve global shutter function, then simultaneous storage of signal charges is enabled, but chip area increases and noise from light leakage and dark current increases
Solution Approach 1:
The imaging device is divided into two separate substrates: a first substrate containing photoelectric conversion elements and a second substrate containing memory elements. This segmentation allows each substrate to be optimized for its specific function while maintaining the global shutter capability, thereby avoiding the chip area increase that would result from integrating all elements on a single substrate.
Solution Approach 2:
A light-blocking film is introduced as an intermediary between the photoelectric conversion elements and the memory elements. This film prevents light from reaching the memory elements through the substrate, thereby eliminating noise from light leakage while maintaining the benefits of the separated substrate configuration.
2Reliability
If photoelectric conversion elements and memory elements are formed on the same substrate, then global shutter function is achieved, but signal quality degrades due to noise from light leakage and dark current
Solution Approach 1:
By separating the photoelectric conversion elements and memory elements onto different substrates, the patent eliminates the direct path for light leakage noise that would affect memory elements on the same substrate. The physical separation inherently reduces this harmful interaction.
Solution Approach 2:
The light-blocking film serves as a protective intermediary that specifically targets and blocks light leakage reaching the memory elements. This additional protective layer, combined with the substrate separation, effectively eliminates the noise from light leakage while preserving the global shutter function.
3Object-affected harmful factors
If wiring layers are positioned to block transmitted light, then light reaching memory elements is prevented, but manufacturing complexity increases
Solution Approach 1:
The light-blocking function is extracted from the wiring layers and implemented as a dedicated light-blocking film. This separation of functions allows the wiring layers to focus on electrical connectivity while the specialized film handles light blocking, thereby reducing manufacturing complexity compared to requiring precisely positioned wiring layers to perform dual functions.
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 reduces noise and maintains signal quality by preventing light from reaching the memory elements, thereby minimizing distortion and improving image fidelity in fast-moving subject imaging.
Implementation Method 1
Each of the first pixels includes a first photoelectric conversion element that is formed in the first semiconductor layer and configured to convert light into a first electrical signal
Implementation Method 2
Each of the second pixels includes a second photoelectric conversion element that is formed in the first semiconductor layer and configured to convert light into a second electrical signal
Implementation Method 3
The first substrate further includes a light-blocking film configured to block light incident on the second photoelectric conversion element
Data Source
AI summary
A solid-state imaging device includes a first substrate and a second substrate electrically connected to the first substrate. The first substrate includes a first semiconductor layer and one or more first wiring layers. The second substrate includes a second semiconductor layer and one or more second wiring layers. The first photoelectric conversion element overlaps any of the one or more first wiring layers at all positions on the first photoelectric conversion element in a planar view of the first substrate. The second photoelectric conversion element does not overlap any of the one or more first wiring layers at some positions on the second photoelectric conversion element in the planar view of the first substrate.