Transfer Gate Trench Defines Doping Interface
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Solution Overview
Problem
The inconsistent interface positions between different doping regions in the transfer gate transistor of image sensor devices result in noise due to shifting during subsequent processes, affecting performance optimization between image lag and dark current.
Innovation Solution
A trench is formed in the gate electrode portion to define a position of a junction between a first region with a first conductivity type and a second region with a second conductivity type or an undoped region, preventing dopant diffusion and maintaining the interface position, thereby stabilizing the transistor's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the interface between different doping regions is defined by a conventional patterning process, then the manufacturing process is simple, but the interface position shifts during subsequent processes resulting in noise
Solution Approach 1:
The gate electrode portion is segmented into a first region and a second region by forming a trench between them. This segmentation not only separates the different doping regions but also the trench itself acts as a physical barrier to prevent dopant diffusion, thereby maintaining interface position consistency without requiring additional complex patterning steps for each pixel.
Solution Approach 2:
The trench formed in the gate electrode portion serves as an intermediary structure between the first and second doping regions. This trench acts as a diffusion barrier that prevents dopant migration, thereby maintaining the interface position between different doping regions consistent across all pixels without requiring complex subsequent patterning processes.
2Reliability
If the interface position between doping regions is not accurately defined, then the manufacturing process is simpler, but noise is generated due to inconsistent interface positions in different pixels
Solution Approach 1:
The trench is formed in the gate electrode portion before the doping process to pre-establish the interface position between different doping regions. This preliminary action ensures that the interface position is accurately defined and maintained throughout subsequent manufacturing processes, preventing noise generation due to position inconsistency across pixels.
Solution Approach 2:
The trench acts as an intermediary structure that physically separates and isolates the different doping regions. By forming this trench beforehand, the interface position is predetermined and protected from shifting during subsequent doping and processing steps, thereby ensuring consistent interface positions across all pixels and reducing noise.
3Ease of manufacture
If dopant diffusion is allowed to occur, then the manufacturing process is simpler, but the interface position shifts affecting performance optimization
Solution Approach 1:
The gate electrode portion is divided into separate regions by forming a trench, which segments the doping areas. This segmentation creates physical boundaries that prevent dopant diffusion between regions while allowing each region to be doped independently using standard doping processes, thus maintaining both manufacturing simplicity and interface position stability.
Solution Approach 2:
The trench serves as an intermediary barrier structure that physically blocks dopant diffusion between the first and second regions. This trench allows the doping process to remain simple and straightforward while ensuring that the interface position between different doping regions remains stable and does not shift during subsequent thermal or chemical processes.
Data Source
AI summary
A method for manufacturing a transfer gate transistor of an image sensor device is disclosed. The transistor includes a substrate, a gate oxide layer on the substrate and a gate electrode portion on the gate oxide layer. The gate electrode portion has a trench or an insulating layer used for accurately defining a first region and a second region in the gate electrode portion, wherein the first region has a first conductivity type, and the second region has a second conductivity type or is an undoped region.