Backside-Illuminated Image Sensor Layout for Higher Full Well Capacity
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Solution Overview
Problem
Current backside illuminated image sensors face challenges in enhancing full well capacity and dynamic range, which are crucial for improving image quality.
Innovation Solution
The design includes a light sensing device that extends from one surface to the opposite surface of a semiconductor layer, with strategically positioned doped regions and gate structures, allowing for an expanded photon collection area, and a manufacturing method that forms these components using epitaxial silicon and thermal processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light sensing device area is increased to improve full well capacity and dynamic range, then image quality is improved, but the device structure becomes more complex
Solution Approach 1:
The light sensing device is configured to extend from the first surface to the second surface of the semiconductor layer, utilizing the vertical dimension to increase the light sensing area. This dimensional transition allows the light sensing device to collect photons from both surfaces, effectively doubling the collection area without requiring a larger planar footprint, thus improving full well capacity and dynamic range while maintaining a compact device structure.
Solution Approach 2:
The semiconductor layer is divided into multiple doped regions (first doped region, second doped region, third doped region) with different conductivity types, creating distinct functional zones within the light sensing device. This segmentation allows independent optimization of each region's properties to enhance light collection efficiency and charge carrier separation, improving image quality without requiring a single large complex structure.
2Area of stationary object
If the light sensing device extends across the gate structure, then photon collection area is increased, but manufacturing precision requirements increase
Solution Approach 1:
The gate structure is formed on the second surface of the semiconductor layer before the light sensing device is completed. This preliminary formation of the gate structure provides a reference framework that guides the subsequent formation of the light sensing device regions, ensuring proper alignment and positioning without requiring high-precision alignment steps during light sensing device fabrication.
Solution Approach 2:
The light sensing device is configured to extend from one side of the gate structure to the other side, with different portions positioned at different locations relative to the gate structure. This local variation in positioning allows optimization of photon collection in different regions while maintaining manufacturability, as not all portions require the same precision relative to the gate structure.
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 configuration enhances the full well capacity and dynamic range of the image sensor, thereby improving image quality by expanding the light sensing device's area and photon collection region.
Implementation Method 1
a light sensing device... The light sensing device extends from the first surface to the second surface
Data Source
AI summary
A backside illuminated image sensor, including a semiconductor layer, a first gate structure, and a light sensing device, is provided. The semiconductor layer has a first surface and a second surface opposite to each other. The first gate structure is disposed on the second surface. The light sensing device is located in the semiconductor layer. The light sensing device extends from the first surface to the second surface.