Optical Refractive Part in Interlayer Insulating Layer for CMOS Image Sensors
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Solution Overview
Problem
As design rules for complementary metal oxide semiconductor (CMOS) image sensors decrease, the size of unit pixels decreases, leading to reduced photosensitivity, and additional structures on the light path, such as metal lines, cause light diffraction and scattering, further decreasing image sensor performance.
Innovation Solution
Incorporating an optical refractive part within the interlayer insulating layer of the image sensor, with a higher refractive index than the surrounding material, to focus light on the photodiode, effectively acting as a microlens and minimizing light deviation caused by metal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microlens is formed on a color filter to increase photosensitivity, then light focusing capability is improved, but additional structures on the light path cause light diffraction and scattering
Solution Approach 1:
The patent extracts the microlens function from the traditional color filter structure and relocates it to the interlayer insulating layer. This separation removes the harmful metal lines and color filter structures from the direct light path while preserving the light-focusing capability of the microlens, thereby reducing light diffraction and scattering while maintaining photosensitivity.
Solution Approach 2:
The patent moves the microlens from the surface level (on the color filter) to an intermediate layer (interlayer insulating layer) within the vertical structure of the image sensor. This dimensional relocation allows the microlens to focus light before it encounters obstructive metal lines, effectively placing the focusing function in a different spatial dimension where it can operate without interference.
2Productivity
If design rule decreases to reduce unit pixel size, then device integration is improved, but photosensitivity decreases
Solution Approach 1:
By relocating the microlens to the interlayer insulating layer, the patent creates an additional vertical dimension for light focusing that is independent of the horizontal pixel density. This allows smaller pixel sizes to maintain adequate photosensitivity because the focused light path is optimized in the vertical dimension rather than being constrained by horizontal pixel pitch.
Solution Approach 2:
The patent applies the microlens structure selectively in the interlayer insulating layer region corresponding to each photodiode, creating localized light focusing zones. This local quality enhancement ensures that each pixel receives optimized light concentration regardless of the overall pixel size, allowing high-density integration while maintaining individual pixel photosensitivity.
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
Enhances photosensitivity by converging and focusing light on the photodiode, reducing light diffraction and scattering, and allowing for improved integration of devices while maintaining signal and power connections.
Implementation Method 1
an optical refractive part disposed within the interlayer insulating layer in a region corresponding to the photodiode for focusing light on the photodiode
Data Source
AI summary
Provided is an image sensor and method for manufacturing the same. The image sensor includes a semiconductor substrate including a photodiode for each unit pixel, an interlayer insulating layer including metal lines on the semiconductor substrate, and an optical refractive part in a region of the interlayer insulating layer corresponding to the photodiode for focusing light on the photodiode. The optical refractive part can be formed by implanting impurities into the interlayer insulating layer.