CMOS Imager Pixel Array Shared Column Line Voltage Supply
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Solution Overview
Problem
Conventional CMOS imaging devices have limitations in increasing fill factor and quantum efficiency due to the need for multiple metal lines, which reduces the effective pixel area and efficiency as devices scale down.
Innovation Solution
The solution involves reducing vertical metal lines by using neighboring column lines to supply the array pixel voltage and sharing horizontal lines, thereby minimizing metal routing and enhancing quantum efficiency and fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple vertical metal lines are used to supply array pixel voltage and readout signals, then pixel control and readout functions are achieved, but fill factor and quantum efficiency are reduced
Solution Approach 1:
The patent combines the array pixel voltage supply line and column line functions into a single vertical metal line structure. The column line serves dual purposes: reading pixel signals and supplying array pixel voltage during reset operations, thereby reducing the number of vertical lines required and increasing the photosensor area.
Solution Approach 2:
The column line is designed to perform multiple functions: it acts as a signal readout path during normal operation and as a voltage supply line during reset operations. This multi-functionality eliminates the need for separate dedicated voltage supply lines, improving fill factor while maintaining full functionality.
2Reliability
If multiple vertical metal lines are used for pixel readout and voltage supply, then complete pixel operation is enabled, but quantum efficiency is reduced
Solution Approach 1:
The patent merges the voltage supply function and signal readout function into the same column line structure, reducing the total metal coverage area over the photosensor and thereby improving quantum efficiency while maintaining complete pixel operation.
Solution Approach 2:
The column line alternates between supplying voltage during reset periods and reading signals during measurement periods. This periodic switching of functions allows a single line to fulfill multiple roles without interference, maintaining operational completeness while improving efficiency.
3Reliability
If separate array pixel voltage supply lines and column lines are used, then voltage supply and signal readout are independent, but device complexity increases
Solution Approach 1:
The patent combines two separate metal line functions (voltage supply and signal readout) into a single column line structure, reducing device complexity by eliminating redundant lines while maintaining functional independence through temporal separation of operations.
Solution Approach 2:
The system uses periodic switching to separate voltage supply and signal readout operations in time, allowing a single shared line to maintain functional independence. The column line supplies voltage during reset phases and reads signals during measurement phases, preventing interference.
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 significantly reduces the number of vertical lines, increases quantum efficiency, and enhances fill factor, leading to improved imaging performance in portable electronic devices.
Implementation Method 1
each one of the pixels including a photosensor, for example, a photogate, photoconductor or a photodiode overlying a substrate for accumulating photo-generated charge
Data Source
AI summary
A method and apparatus providing an imager with shared power supply and readout lines. A pixel array has a plurality of pixels arranged in rows and columns. Each column of the array comprises a column line coupled to receive pixel signals from the pixels in the column and selectively operated to provide a supply voltage to at least one pixel in a different column.