Image Sensor Pixel Gate Structure for Higher Fill Factor
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Solution Overview
Problem
Conventional image sensor devices have a reduced fill factor due to laterally extending pixel transistors, which limits the area available for photodiodes, thereby decreasing quantum efficiency and overall performance.
Innovation Solution
The image sensor device incorporates pixel transistors with gate features that partially extend into the semiconductor substrate, reducing the lateral distance and allowing more photodiodes to be disposed over a given chip area, thereby increasing the fill factor and quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixel transistors are planarly formed with gate features extending only laterally along the major surface, then the manufacturing process is simple, but the fill factor is reduced due to increased lateral space occupation
Solution Approach 1:
The gate feature is configured to extend in both lateral directions along the major surface and vertically into the semiconductor substrate, transitioning from a two-dimensional planar structure to a three-dimensional structure. This vertical extension reduces the lateral footprint of the transistor, thereby increasing the fill factor while maintaining manufacturing feasibility through standard semiconductor processing techniques.
2Area of stationary object
If gate features extend partially into the semiconductor substrate, then the fill factor is increased by reducing lateral distance, but the manufacturing process becomes more complex
Solution Approach 1:
The gate feature extends vertically into the semiconductor substrate, utilizing the third dimension to reduce lateral space occupation. This structural change increases the fill factor while the added complexity is managed through integration with existing semiconductor fabrication processes.
3Reliability
If more photodiodes are disposed over a given chip area, then the quantum efficiency is improved, but the transistor structure must occupy less lateral space
Solution Approach 1:
By extending the gate feature vertically into the semiconductor substrate, the transistor's lateral footprint is reduced. This allows more photodiodes to be packed into a given chip area, thereby increasing the fill factor and improving quantum efficiency without requiring additional lateral space.
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 significantly enhances the performance of the image sensor device by increasing the fill factor and quantum efficiency while maintaining the same chip area, improving the detection and conversion of incident light into electrical signals.
Implementation Method 1
Each pixel includes at least one photosensitive diode (hereinafter 'photodiode') configured to detect the incident light and convert the detected incident light into an electrical signal (e.g., a photocurrent/current signal)
Data Source
AI summary
A semiconductor device includes: a photodiode formed in a substrate; and at least one transistor having a gate feature that comprises a first portion and a second portion coupled to an end of the first portion, the first portion disposed above and extending along a major surface of the substrate and the second portion extending from the major surface of the substrate into the substrate, wherein the photodiode and the at least one transistor at least partially form a pixel.