Multi-Layer Micro Lens Reflow for Image Sensor Light Concentration
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Solution Overview
Problem
The challenge in manufacturing image sensors is to enhance photo sensitivity while maintaining or increasing the fill factor, which is limited by the decreasing pixel size and the area of the photodiode.
Innovation Solution
The method involves forming a semiconductor substrate with multiple pixel regions and using a series of pattern formations and reflow processes to create micro lenses on each pixel region, optimizing the surface area and curvature for improved light concentration, specifically forming sub-micro and micro lenses on red, green, and blue pixel regions to enhance light focusing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of photodiode is increased to improve photo sensitivity, then photo sensitivity improves, but pixel size must be increased which limits the fill factor
Solution Approach 1:
The patent transitions from a single-layer micro lens structure to a multi-layer lens structure (first micro lens layer and second micro lens layer), adding a vertical dimension to the optical path. This allows light concentration without increasing the horizontal pixel area, resolving the contradiction between photo sensitivity and pixel size constraints.
Solution Approach 2:
The patent implements nested micro lenses where a first micro lens is formed within or alongside a second micro lens of different material and optical properties. This nested configuration enables multiple optical functions within the same pixel footprint, improving light concentration efficiency without increasing pixel area.
2Ease of manufacture
If a single-layer micro lens is formed, then the manufacturing process is simple, but light concentration efficiency is insufficient
Solution Approach 1:
The patent divides the single micro lens into multiple segments (first micro lens layer and second micro lens layer) with different materials and optical characteristics. Each layer performs a specific optical function, and their combination achieves superior light concentration efficiency while maintaining manufacturability through sequential formation processes.
Solution Approach 2:
The patent employs composite material structures where the first micro lens layer and second micro lens layer are made of different materials with complementary optical properties. This composite approach optimizes light concentration for different wavelengths and angles, improving overall efficiency without significantly complicating the manufacturing 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
This approach improves the concentration efficiency of light and reduces light loss, thereby increasing the photo sensitivity of the image sensor by tailoring the micro lens curvature and coverage to the specific wavelength of each pixel region.
Implementation Method 1
first performing a reflow of the first pattern to form a sub-micro lens on the first pixel region
Implementation Method 2
first performing a reflow of the first and second patterns to form a sub-micro lens on the first pixel region and a first micro lens on the second pixel region
Implementation Method 3
form a first micro lens covering the sub-micro lens... form a second micro lens covering the sub-micro lens... improves the concentration efficiency of light
Data Source
AI summary
The method of manufacturing an image sensor includes providing a semiconductor substrate including a first pixel region, first forming a first pattern on the first pixel region, first performing a reflow of the first pattern to form a sub-micro lens on the first pixel region, second forming a second pattern on the sub-micro lens, and second performing a reflow of the second pattern to form a first micro lens covering the sub-micro lens.