CMOS Image Sensor Wiring Fault Detection in Stacked Pixel Blocks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing imaging devices face challenges in inspecting wiring faults within pixel rows or columns with minimal additional circuits, leading to inefficiencies in detecting open circuit faults in the complex wiring networks of CMOS image sensors.
Innovation Solution
An imaging device is designed with a stacked substrate configuration, incorporating a fault detection circuit that connects wiring lines in series to detect faults by measuring potential differences across the chain, using identical N-channel MOS transistors for efficiency and minimizing circuit overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wiring lines are connected in series to detect faults, then wiring fault detection capability is improved, but circuit complexity increases
Solution Approach 1:
The pixel array is divided into multiple pixel blocks, and wiring lines within each block are connected in series to form a wiring chain. This segmentation allows fault detection to be performed on smaller, manageable units rather than the entire wiring network, improving detection capability while controlling circuit complexity through localized implementation.
Solution Approach 2:
The same N-channel MOS transistors used in pixel circuits are repurposed for fault detection by connecting their source and drain to form series connections in the wiring chain. This multi-functional use of existing components enables wiring fault detection without adding dedicated detection transistors, thereby improving reliability while minimizing circuit complexity increase.
2Measurement precision
If fault detection circuit is added to each pixel block, then wiring fault detection precision is improved, but area overhead increases
Solution Approach 1:
The fault detection function is achieved by utilizing the inherent electrical properties of the wiring lines and existing MOS transistors within each pixel block. By measuring voltage distribution along the series-connected wiring chain, the system performs self-diagnosis without requiring external detection equipment or additional dedicated circuit area, thus improving detection precision while minimizing area overhead.
Solution Approach 2:
The fault detection mechanism relies on measuring changes in voltage potential along the wiring chain when a fault occurs. By monitoring parameter changes (voltage distribution) rather than adding physical detection components, the system achieves precise fault localization with minimal area overhead, as voltage measurement can be performed using existing circuit nodes.
3Ease of manufacture
If N-channel MOS transistors are used for fault detection, then ease of manufacture is improved, but circuit complexity increases
Solution Approach 1:
N-channel MOS transistors that are already part of the pixel circuit design are utilized for fault detection by reconfiguring their connections to form series wiring chains. This approach leverages the existing transistor design and manufacturing process, improving ease of manufacture while the series connection configuration provides fault detection functionality with controlled circuit complexity.
Solution Approach 2:
The fault detection implementation uses uniform N-channel MOS transistors throughout the pixel array, maintaining consistency with the existing pixel circuit design. This homogeneity simplifies manufacturing by using a single transistor type and process, while the systematic series connection approach manages circuit complexity through regular, repeatable patterns across the array.
Data Source
AI summary
In one example, an imaging device includes stacked first and second substrates. The first substrate has an array of light receiving pixels divisible into pixel blocks and the second substrate has a pixel control portion that controls the pixels. The first substrate includes a first wiring line that transmits a first voltage, a second wiring line that transmits a second voltage, and a fault detection circuit that detects a wiring fault for each pixel block. The fault detection circuit detects a wiring fault by connecting wiring lines corresponding to pixel columns or pixel rows in series in each pixel block, connecting one of the ends of a wiring chain connected in series in each pixel block to the first wiring line, connecting the other end to the second wiring line, and detecting a wiring fault based on a potential at an intermediate position of the wiring chain.