Pixel Isolation Trench Doping for Image Sensor Electrical Isolation
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Solution Overview
Problem
Existing image sensors face challenges in achieving improved electrical and optical characteristics, particularly in terms of complexity, power consumption, and manufacturing costs, while also requiring high resolution and integration capabilities.
Innovation Solution
A method of fabricating an image sensor involves forming a semiconductor substrate, creating a pixel isolation trench, doping a liner insulating layer with dopants, and performing a thermal treatment process to diffuse these dopants into a semiconductor layer, along with forming a pixel isolation structure that includes a semiconductor pattern and a liner insulating pattern with higher dopant concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pixel isolation structure is formed to define pixel regions, then electrical isolation between pixels is improved, but manufacturing complexity increases
Solution Approach 1:
The liner insulating layer is formed and doped with dopants before the semiconductor filling layer is deposited. This preliminary doping action allows the isolation structure to be prepared in advance, simplifying subsequent manufacturing steps while ensuring proper electrical isolation is established before pixel formation begins.
Solution Approach 2:
The liner insulating layer is selectively formed only in the pixel isolation trench regions, providing localized electrical isolation where needed. The dopants are concentrated in this liner layer at the trench interfaces, creating high doping concentration zones that provide effective electrical isolation between adjacent pixel regions without requiring complex structures throughout the entire device.
2Reliability
If dopants are diffused into the semiconductor layer through thermal treatment, then electrical characteristics are improved, but manufacturing time increases
Solution Approach 1:
The dopants are pre-loaded into the liner insulating layer during the insulation film formation process, before the semiconductor filling layer is deposited. This preliminary preparation eliminates the need for separate, time-consuming doping steps later in the manufacturing process, as the thermal treatment simply activates the pre-positioned dopants.
Solution Approach 2:
The liner insulating layer serves as an intermediary reservoir for the dopants. Instead of directly doping the semiconductor layer (which would require precise, time-consuming control), the dopants are first introduced into the liner layer, which then acts as a source that releases dopants into the semiconductor layer during thermal treatment, simplifying the overall process.
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
The method enhances the electrical and optical performance of the image sensor by reducing complexity, power consumption, and manufacturing costs, while enabling high-resolution imaging and integration on a single chip.
Implementation Method 1
performing a thermal treatment process on the semiconductor substrate. The thermal treatment process may diffuse the dopants, which are contained in the liner insulating layer, into the semiconductor layer
Data Source
AI summary
A method of fabricating an image sensor includes forming a semiconductor substrate of a first conductivity type, forming a pixel isolation trench in in the semiconductor substrate to define pixel regions, forming a liner insulating layer in the pixel isolation trench, doping the liner insulating layer with dopants of a first conductivity type, forming a semiconductor layer on the liner insulating layer to fill the pixel isolation trench after the doping of the dopants, and performing a thermal treatment process on the semiconductor substrate.