Image Sensor Floating Diffusion Node Voltage Boosting via Segmented Light Shielding
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Solution Overview
Problem
Image sensors face challenges in boosting the voltage of a floating diffusion node while maintaining low power consumption and high resolution, as increasing operating voltage or capacitance leads to increased power consumption and larger pixel sizes.
Innovation Solution
An image sensor design that includes a floating diffusion node and storage elements formed in a semiconductor substrate, with separate light-shielding materials and voltage supply lines, allowing for a positive voltage to be applied to one light-shielding material while maintaining a ground voltage for the other, thereby boosting the floating diffusion node's voltage without increasing overall voltage or capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the operating voltage applied to pixels is increased to increase the amount of charges that can be stored at the floating diffusion node, then the charge storage capacity is improved, but the power consumption of the image sensor increases
Solution Approach 1:
The light-shielding material is divided into two separate parts: a first light-shielding material formed over the floating diffusion node and a second light-shielding material formed over the storage diode. These separate structures allow independent voltage control, enabling the first light-shielding material to be boosted to a higher voltage than the second light-shielding material, thereby increasing charge storage capacity without proportionally increasing overall power consumption.
Solution Approach 2:
Different voltage levels are applied to different regions of the light-shielding material. Specifically, the first light-shielding material is boosted to a voltage higher than that of the second light-shielding material during specific time periods. This local voltage differentiation allows the floating diffusion node region to store more charges while avoiding the need to increase voltage across the entire pixel structure, thus reducing overall power consumption.
2Quantity of substance
If the capacitance of the floating diffusion node is increased to increase the amount of charges that can be stored, then the charge storage capacity is improved, but the size of pixels increases
Solution Approach 1:
Instead of increasing the physical capacitance of the floating diffusion node (which would require larger area), the patent changes the voltage parameter by boosting the first light-shielding material to a higher voltage than the second light-shielding material. This voltage parameter change effectively increases the charge storage capacity Q=C×V without requiring an increase in capacitance C, thereby maintaining small pixel size while achieving higher charge storage capacity.
3Quantity of substance
If the voltage of the floating diffusion node is boosted to increase charge storage capacity, then the charge storage capacity is improved, but the power consumption increases
Solution Approach 1:
The light-shielding material is segmented into two independently controllable parts, allowing selective voltage boosting only where needed (over the floating diffusion node) rather than across the entire structure. This targeted approach increases charge storage capacity locally while minimizing the overall energy consumption of the system.
Solution Approach 2:
The voltage boosting of the first light-shielding material is applied periodically or selectively during specific time periods rather than continuously. The first light-shielding material is boosted to a voltage higher than the second light-shielding material during specific intervals, which reduces average power consumption while still achieving the necessary charge storage capacity when needed.
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 design enhances the charge storage capacity of the floating diffusion node, enabling efficient image sensing with reduced power consumption and smaller pixel sizes, suitable for high-resolution image processing systems.
Implementation Method 1
a first light-shielding material formed over the floating diffusion node, and a second light-shielding material formed over the storage diode
Implementation Method 2
Each of the pixels includes a photoelectric conversion element that performs photoelectric conversion
Data Source
AI summary
An image sensor capable of boosting a voltage of a floating diffusion node is provided. The image sensor includes a floating diffusion node and a storage element which are in a semiconductor substrate. The image sensor includes a first light-shielding material formed over the floating diffusion node, and a second light-shielding material formed over the storage diode. The second light-shielding material is separated from the first light-shielding material. The image sensor also includes a first voltage supply line configured to apply a first voltage to the first light-shielding material and a second voltage supply line configured to apply a second voltage lower than the first voltage to the second light-shielding material.