CMOS X-ray Sensor Non-Rectangular Pixel Layout
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Solution Overview
Problem
Current MOS and CMOS image sensors in X-ray imaging face limitations due to their small size, which restricts their ability to image larger body organs, and the challenge of integrating multiple sensors while maintaining signal integrity and avoiding defect zones at the wafer edges.
Innovation Solution
A method for producing a monolithic imaging device with a non-rectangular image zone on a single substrate, featuring a set of pixels arranged in rows and columns with non-uniform pixel density, where row and column addressing blocks are integrated on the same substrate, allowing for efficient addressing and reading of pixels, and the use of photolithography to optimize wafer surface usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If MOS or CMOS image sensors are made on standard silicon wafers (100-300mm diameter), then manufacturing cost is controlled, but the sensor area is limited and cannot image larger body organs
Solution Approach 1:
The patent divides the image sensor into multiple separate sensors, each made on a standard silicon wafer. These segmented sensors are then arranged in a tiled configuration to form a larger composite imaging area, enabling imaging of larger body organs while maintaining compatibility with standard wafer manufacturing processes
Solution Approach 2:
The patent transitions from a single large-area sensor plane to a three-dimensional arrangement of multiple smaller sensors stacked or tiled together. This dimensional approach allows the system to achieve large effective imaging area without requiring a single oversized wafer, thus avoiding prohibitive manufacturing costs
2Area of stationary object
If multiple CMOS image sensors are abutted together to increase imaging area, then larger organs can be imaged, but pixel abutment is penalized or prevented at addressing block locations and defect zones are denser at wafer edges
Solution Approach 1:
The patent employs non-rectangular sensor geometries (such as hexagonal or irregular shapes) that are optimized for tiling. This asymmetric design allows sensors to be arranged in patterns that minimize the impact of addressing blocks and defect zones at edges, improving overall signal integrity while maintaining large imaging area
Solution Approach 2:
The patent applies different design characteristics to different regions of the sensor array. Central regions use standard high-density pixel configurations, while peripheral regions incorporate adjusted pixel layouts or exclusion zones that account for addressing block locations and wafer edge defect densities, thereby maintaining overall reliability
3Ease of manufacture
If rectangular geometry is used for MOS or CMOS image sensors on silicon wafers, then manufacturing is simplified, but defect zones at wafer edges reduce the usable surface area
Solution Approach 1:
The patent adopts non-rectangular sensor geometries such as circular, hexagonal, or other curved boundary shapes that better utilize the circular silicon wafer substrate. This eliminates the corner waste inherent in rectangular designs and maximizes the usable imaging area while maintaining manufacturing simplicity through standard photolithography processes
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 approach enables the creation of larger, more efficient CMOS sensors with a higher surface area to cost ratio, capable of imaging larger areas without the need for multiple sensors, while minimizing defects and signal disruptions.
Implementation Method 1
A method for producing by photolithography an imaging device on a semiconductor wafer
Data Source
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AI summary
The invention relates to the field of digital imaging devices, in particular devices for X-ray medical imaging. The invention relates to an imaging device including pixels that are individually addressed by addressing circuits, and to a method for producing such an imaging device via photolithography. The imaging device comprises a sensor (61), the surface area of which is greater than or equal to 10 cm2, and which includes: an image area (23) produced on a single substrate (22) and comprising a set of pixels (24) arranged in lines and columns, the number of pixels per column not being uniform for all of the pixel columns, each pixel (24) collecting electrical charges generated by a photosensitive element; line conductors connecting the pixels line-by-line; column conductors connecting the pixels column-by-column; line addressing units (12) connected to the line conductors in order to address each line of pixels individually; and column reading units connected to the column conductors in order to read the electrical charges collected by the pixels (24) of the line selected by the line addressing units (12), the column reading units being located at the periphery of the image area (23), the line addressing units (12) and the column reading units being produced on the same substrate (22) as the image area.