Vertical Gate Image Sensor Structure for Charge Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors face challenges in preventing potential humps and enhancing charge transfer efficiency, particularly as pixel sizes are miniaturized, which affects the performance and reliability of image sensors in various applications.
Innovation Solution
The implementation of a vertical gate structure with a spacer between the dual vertical extensions and the substrate, along with a gate insulation layer, helps prevent potential humps and improves charge transfer efficiency by alleviating field concentration at the active region edges, while also minimizing gate contact area and misalignment risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional planar gate structure is used, then the manufacturing process is simple, but potential humps form and charge transfer efficiency decreases
Solution Approach 1:
The gate structure transitions from a conventional planar (2D) configuration to a vertical three-dimensional structure. The vertical gate extends downward from the surface into the substrate, creating a 3D configuration that eliminates potential humps at gate edges while improving charge transfer efficiency. This dimensional change allows the gate to interact with charge carriers throughout a greater volume without creating harmful field concentration points.
Solution Approach 2:
The vertical gate is segmented into multiple components: a vertical extension portion extending from the surface into the substrate, and a horizontal extension portion extending laterally at a lower level. This segmentation allows each portion to perform its specific function - the vertical portion prevents potential hump formation, while the horizontal portion maintains electrical connection - thereby resolving the contradiction between improved reliability and structural complexity.
2Measurement precision
If pixel size is miniaturized to increase resolution, then image sensor performance improves, but potential hump formation and field concentration become more severe
Solution Approach 1:
By transitioning to a vertical gate structure that extends into the substrate depth dimension, the invention eliminates potential humps that would otherwise form at the edges of miniaturized planar gates. The vertical configuration distributes electric fields more evenly throughout the reduced pixel volume, preventing harmful field concentration even as horizontal dimensions are reduced to achieve higher resolution.
Solution Approach 2:
The spacer structure acts as an intermediary element positioned between the vertical gate and the substrate. This intermediary maintains optimal spacing that prevents direct contact-induced field concentration while allowing the vertical gate to effectively suppress potential humps. The spacer enables the vertical gate to function properly in miniaturized pixels without creating harmful electric field patterns.
3Reliability
If a vertical gate structure is implemented to prevent potential humps, then charge transfer efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The vertical gate is divided into functionally distinct segments: a vertical extension portion for preventing potential humps and a horizontal extension portion for electrical connection. This segmentation allows each portion to be optimized independently for its specific function, simplifying the overall manufacturing approach by clearly defining the role and dimensions of each component rather than requiring complex integrated optimization.
Solution Approach 2:
The vertical gate structure inherently provides its own alignment and positioning functions. The vertical extension naturally aligns with the photodiode region below, and the horizontal extension automatically positions itself for electrical connection, reducing the need for complex external alignment procedures during manufacturing. The structure serves its own positioning needs, simplifying the manufacturing process.
Data Source
AI summary
An image sensor includes a substrate, a vertical gate including a vertical extension vertically extending into the substrate from a top of the substrate, and a horizontal extension extending in parallel with a top surface of the substrate from a top of the vertical extension, a photodiode (PD) disposed under the vertical gate inside the substrate, a spacer disposed between the horizontal extension and the substrate, and a gate insulation layer. A bottom surface and side surfaces of the vertical extension and a bottom surface of the horizontal extension are covered by the gate insulation layer, and the spacer is disposed between the substrate and the gate insulation layer of the horizontal extension.