Image Sensor Fabrication via Plasma Doping and Annealing
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Solution Overview
Problem
Existing image sensor fabrication methods face challenges in achieving uniform impurity concentration throughout the photoelectric conversion part, which can lead to issues like dark current and white spots.
Innovation Solution
A method involving plasma doping and annealing processes to form impurity regions in a semiconductor substrate, ensuring uniform impurity distribution and concentration within the photoelectric conversion part, including the formation of deep trenches and through holes for enhanced doping precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional doping methods are used to form impurity regions in the semiconductor substrate, then the doping process can be completed, but the impurity concentration becomes non-uniform throughout the photoelectric conversion part, leading to dark current and white spots
Solution Approach 1:
The doping process is segmented into multiple sequential steps: forming deep trenches to divide the substrate into regions, performing plasma doping to create impurity regions adjacent to trench sidewalls, and using annealing to diffuse impurities uniformly. This segmentation allows precise control over impurity distribution, achieving uniform concentration throughout the photoelectric conversion part while eliminating dark current and white spots.
2Manufacturing precision
If deep trenches are formed and plasma doping is performed to achieve uniform impurity distribution, then the impurity concentration uniformity is improved, but the fabrication process complexity increases
Solution Approach 1:
Deep trenches are formed preliminarily before the doping process. This preliminary structuring creates defined regions that guide subsequent plasma doping, ensuring impurities are deposited uniformly in the photoelectric conversion areas. The pre-formed trenches act as templates that simplify the doping step, making the increased process complexity worthwhile by guaranteeing uniform impurity concentration.
3Measurement precision
If plasma doping is performed to form impurity regions adjacent to deep trench sidewalls, then the doping precision is improved, but the process time and energy consumption increase
Solution Approach 1:
Plasma doping is applied locally to specific regions adjacent to the deep trench sidewalls, rather than uniformly across the entire substrate. This localized approach concentrates the doping action where it is needed most, achieving high precision in the photoelectric conversion areas while minimizing unnecessary processing time and energy consumption in other regions.
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 achieves a uniform impurity concentration throughout the photoelectric conversion part, improving the image sensor's performance by reducing dark current and white spots, and enhancing light-receiving efficiency.
Implementation Method 1
performing a first plasma doping process to form a first impurity region in a portion of the semiconductor substrate adjacent to inner sidewalls and a bottom surface of the deep trench
Implementation Method 2
performing an annealing process to diffuse the first impurities from the first impurity region into the semiconductor substrate to form a photoelectric conversion part
Data Source
AI summary
A method of fabricating an image sensor is provided. The method includes comprises forming a deep trench in a semiconductor substrate, performing a first plasma doping process to form a first impurity region a portion of in the semiconductor substrate adjacent to inner sidewalls and a bottom surface of the deep trench, the first impurity region being doped with first impurities of a first conductivity type, and performing an annealing process to diffuse the first impurities from the first impurity region into the semiconductor substrate to form a photoelectric conversion part.