Image Sensor Reset Transistor Drain Voltage Control
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Solution Overview
Problem
Current image sensors face challenges in achieving high performance and reducing dark current, which leads to random noise, particularly due to the limitations in the design of the reset drain voltage and its impact on the floating diffusion region.
Innovation Solution
The image sensor design incorporates a reset transistor with a reset drain voltage ranging from 0.1V to 1.0V, independent of the pixel voltage, to effectively control the reset operation and reduce dark current, thereby minimizing random noise. This is achieved through a specific configuration of transistors and voltage control mechanisms within the image sensor's pixel structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reset drain voltage is increased to improve reset operation, then the reset efficiency is improved, but the dark current increases leading to more random noise
Solution Approach 1:
The patent applies parameter changes by setting the reset drain voltage to a specific range (0.1V to 1.0V) that is independent of the pixel voltage. This optimized voltage parameter achieves effective reset operation while minimizing dark current generation in the floating diffusion region, thereby reducing random noise without sacrificing reset efficiency
Solution Approach 2:
The patent implements local quality by applying a specialized voltage condition specifically to the reset drain electrode that differs from the general pixel voltage. This localized voltage control targets the reset transistor's drain region to optimize reset performance while controlling dark current, without affecting other parts of the pixel circuit
2Reliability
If the reset drain voltage is made independent of pixel voltage, then the reset operation is optimized, but the circuit complexity increases
Solution Approach 1:
The patent achieves universality by using the reset transistor's drain electrode to serve multiple functions: it provides the reset function while also being controlled by an independent voltage that optimizes both reset efficiency and dark current suppression. This multi-functional approach eliminates the need for separate control circuits
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
The proposed solution significantly reduces dark current in the floating diffusion region, leading to a decrease in random noise and improved image sensor performance by optimizing the reset drain voltage and transistor control.
Implementation Method 1
a first photoelectric conversion layer which is disposed on a substrate. The first photoelectric conversion layer is configured to convert light received on the first photoelectric conversion layer to a first signal
Data Source
AI summary
An image sensor includes a first photoelectric conversion layer that is configured to convert light to a first signal. The image sensor also includes a transfer transistor. The transfer transistor includes a storage node region which stores the first signal. The transfer transistor also includes a transfer gate which transfers the stored first signal, and a floating diffusion region that receives the first signal. The image sensor includes a reset transistor that resets the floating diffusion region, and a drive transistor which receives a pixel voltage. The drive transistor generates an output voltage. The image sensor also includes a selection transistor which outputs the output voltage. A reset drain voltage is applied to a drain electrode of the reset transistor, and is independent of the pixel voltage. The reset drain voltage ranges from about 0.1V to about 1.0V.