Image Sensor Impurity Regions for Light Collection and Blooming
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Solution Overview
Problem
Image sensors with color filters, such as those using Bayer filters, face challenges in forming photoelectric-converting units to effectively collect light of different wavelengths without increasing manufacturing costs and complexity, as deep implantation of impurities can lead to 'blooming' due to diffusion into adjacent regions.
Innovation Solution
The image sensor design includes first and second photoelectric converting units with impurity regions of equal depth but varying widths, with the second impurity region having a smaller width and shallower depth than the first, and a third impurity region with equal width to the upper regions, optimized for red, green, and blue light detection, respectively, using a single photolithography process to reduce manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoelectric-converting units are formed deeply to collect all incident light, then light collection efficiency is improved, but impurities diffuse into adjacent regions causing blooming
Solution Approach 1:
The patent applies local quality by forming impurity regions with different widths at different locations. Specifically, the first impurity region (for red light) has a larger width than the second impurity region (for green light), which in turn is wider than the third impurity region (for blue light). This local variation in impurity region width allows each photoelectric-converting unit to collect light efficiently at its specific depth while preventing impurity diffusion into adjacent regions, thus resolving the blooming problem without sacrificing light collection efficiency.
2Reliability
If photoelectric-converting units are formed at different depths for different wavelengths, then light collection for different wavelengths is improved, but manufacturing complexity and cost increase due to multiple photomask processes
Solution Approach 1:
The patent merges the formation of multiple impurity regions into a single ion implantation process. By designing the ion implantation conditions (energy, dose, angle) appropriately, the first, second, and third impurity regions are formed simultaneously in one step, rather than requiring separate photomask and implantation processes for each wavelength. This significantly reduces manufacturing complexity while maintaining the ability to collect different wavelengths effectively.
Solution Approach 2:
The patent utilizes parameter changes in the ion implantation process to create different impurity region depths and widths. By varying implantation energy, dose, and angular distribution, the first, second, and third impurity regions are formed with different characteristics (depths and widths) suitable for red, green, and blue light detection respectively, all within a single implantation process.
3Reliability
If impurities are implanted deeply into the semiconductor substrate, then photoelectric-converting units can collect deeper penetrating light, but impurity diffusion into adjacent regions increases
Solution Approach 1:
The patent applies local quality by creating impurity regions with different widths tailored to their specific locations and functions. The first impurity region has a larger width to accommodate deeper light penetration for red wavelengths, while the third impurity region has a smaller width for blue wavelengths that penetrate less deeply. This local adaptation maintains manufacturing precision and prevents blooming while enabling effective light collection at different depths.
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 enhances color reproducibility and reduces blooming by efficiently capturing charges from different wavelengths while simplifying the manufacturing process, improving the reliability and productivity of image sensors.
Implementation Method 1
Each unit pixel includes a photoelectric-converting unit that accumulates charges corresponding to the amount of incident light
Implementation Method 2
when impurities that form the photoelectric-converting units are implanted deeply into the semiconductor substrate, it is likely that the impurities will diffuse into adjacent regions
Data Source
AI summary
An image sensor includes a semiconductor layer, and first and second photoelectric converting units including first and second impurity regions in the semiconductor layer that are spaced apart from each other and that are at about an equal depth in the semiconductor layer, each of the impurity regions including an upper region and a lower region. A width of the lower region of the first impurity region may be larger than a width of the lower region of the second impurity region, and widths of upper regions of the first and second impurity regions are equal.