Image Sensor Gate Dielectric Joint for Charge Transfer
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Solution Overview
Problem
Conventional image sensor devices face challenges in achieving simultaneous efficient charge transfer and preventing charge leakage due to the potential energy distribution of the channel being unsuitable for turn-on and turn-off statuses in the transfer transistor.
Innovation Solution
The design incorporates two gate dielectric layers with different thicknesses, forming a joint above the channel, where the first gate dielectric layer is thicker than the second, creating distinct potential energy statuses that facilitate efficient charge transfer when the gate is on and prevent leakage when it is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transfer transistor structure with uniform gate dielectric layer is used, then the device is simple to manufacture, but charge transfer efficiency is insufficient and charge leakage cannot be prevented
Solution Approach 1:
The gate dielectric layer is segmented into two distinct layers: a first gate dielectric layer and a second gate dielectric layer with different thicknesses. This segmentation allows different regions of the channel to have different potential energy distributions, thereby improving charge transfer efficiency while preventing charge leakage.
Solution Approach 2:
Different thicknesses of gate dielectric layers are applied to different locations above the channel. The first gate dielectric layer has a greater thickness than the second gate dielectric layer, creating localized variations in electric field distribution and potential energy that optimize charge transfer at specific channel regions.
2Reliability
If process adjustment methods such as channel implantation doping are used to alter threshold voltage, then the transfer transistor can be turned on and off, but charge leakage and residual charge backflow cannot be prevented
Solution Approach 1:
Instead of adjusting threshold voltage through conventional doping methods in the horizontal plane, the invention introduces a vertical dimension by varying the thickness of gate dielectric layers at different positions above the channel. This dimensional approach creates distinct potential energy barriers that prevent charge leakage and backflow without requiring additional doping steps.
3Reliability
If a single thickness gate dielectric layer is used, then the manufacturing process is simple, but the potential energy distribution cannot simultaneously support efficient charge transfer and prevent charge leakage
Solution Approach 1:
The thickness parameter of the gate dielectric layer is changed at different locations to create the first and second gate dielectric layers. By controlling the thickness parameter differently in different regions, the invention achieves optimal potential energy distribution for both charge transfer and charge isolation functions.
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 charge transfer efficiency by ensuring charges are transferred to the voltage transfer region without accumulation in the channel and prevents backflow of residual charges, improving the overall performance of the image sensor device.
Implementation Method 1
the potential energy distribution of the channel presents one high status and one low status during turning on or turning off due to the structural design of the two gate dielectric layers with various thicknesses therebetween
Data Source
AI summary
The present invention provides an image sensor device including a substrate, a channel formed in the substrate, a photoelectric transfer region formed in the substrate located at one side of the channel, a voltage transfer region formed in the substrate located at the other side of the channel, a first gate dielectric layer formed on the substrate, a second gate dielectric layer formed on the substrate, wherein the first gate dielectric layer and the second gate dielectric layer have a joint above the channel, and the thickness of the first gate dielectric layer is thicker than that of the second gate dielectric layer, and a gate formed on the first gate dielectric layer and the second gate a is dielectric layer. The present invention also provides a method for fabricating the image sensor device.