Image Sensor Pixels With Deep Trench Isolation Photo Gate
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Solution Overview
Problem
Current image sensors, particularly CMOS image sensors, face inefficiencies in sensing and signal conversion, which affect image quality and signal-to-noise ratio, especially under varying light conditions.
Innovation Solution
The image sensor employs a deep trench isolation (DTI) region as a photo gate, with adjustable photo-gate control signals to manage the number of electrons in each pixel's photo diode, using negative or higher voltages depending on gain requirements, and incorporates an analog-to-digital converter and output compensating circuit to enhance signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photo-gate control signal voltage is increased to reduce leakage current and improve signal-to-noise ratio, then sensing efficiency is improved, but the number of total electrons in the photo diode decreases
Solution Approach 1:
The patent applies dynamics by making the photo-gate control signal voltage adjustable rather than fixed. The voltage can be dynamically changed based on operating conditions (e.g., -3V to -6V) to optimize performance. This allows the system to adapt between capturing more electrons (lower voltage) or reducing leakage current (higher voltage) depending on lighting conditions and required gain, resolving the contradiction between signal-to-noise ratio and electron quantity.
2Reliability
If the photo-gate control signal voltage is increased to reduce leakage current, then sensing efficiency is improved, but the photo diode size decreases
Solution Approach 1:
The patent applies parameter changes by adjusting the photo-gate control signal voltage to control the depletion region width of the photo diode. By changing this voltage parameter, the system can reduce leakage current (improving sensing efficiency) while accepting a reduction in effective photo diode area. This parameter adjustment resolves the contradiction by allowing optimization of sensing efficiency at the cost of reduced photo diode size.
3Measurement precision
If the photo-gate control signal voltage is increased to improve signal quality, then signal-to-noise ratio increases, but gain control becomes more complex
Solution Approach 1:
The patent applies parameter changes by using a single controllable voltage parameter (photo-gate control signal) to achieve multiple functions: controlling leakage current, adjusting gain, and optimizing signal-to-noise ratio. By changing this one parameter, the system accomplishes what would otherwise require multiple control mechanisms, thereby improving signal quality without proportionally increasing device complexity.
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 improves sensing efficiency and signal-to-noise ratio by controlling electron numbers and leakage currents, optimizing image quality across different light intensities.
Implementation Method 1
The pixel array is configured to receive optical signals, convert the optical signals to electric signals
Data Source
AI summary
An image sensor includes a row driver, a pixel array, an analog-to-digital converter, and an output compensating circuit. The row driver generates a photo-gate control signal, a storage control signal, a transfer control signal, a reset control signal and a row selecting signal. The pixel array includes a plurality of pixels, and each pixel uses a deep trench isolation (DTI) region as a photo gate. The pixel array receives optical signals, converts the optical signals to electric signals, and outputs the electric signals as image signals in response to the photo-gate control signal, the storage control signal, the transfer control signal, the reset control signal, and the row selecting signal. The analog-to-digital converter performs an analog-to-digital conversion on the image signals to generate first signals, and the output compensating circuit compensates the first signals.