Microlens Array Alignment via Centering Structures
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Solution Overview
Problem
Conventional gapless microlens arrays in integrated circuits suffer from misalignment issues during the reflow process, leading to crosstalk between pixels, reduced light conversion efficiency, increased noise, and color shading problems.
Innovation Solution
Incorporating centering structures in the first layer of microlenses to align the second layer of lenses accurately, utilizing surface tension and photolithographic processes to ensure precise alignment and minimize misalignment effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reflowed gapless microlens arrays are formed in two separate groups with separate layers, then the manufacturing process can be completed, but misalignment occurs between the first and second sets of microlenses causing crosstalk, reduced light conversion efficiency, increased noise, and color shading
Solution Approach 1:
The patent introduces alignment marks as intermediary reference structures that mediate the alignment between first and second sets of microlenses. These marks serve as a common reference frame that enables precise positioning of subsequent lens layers, resolving the misalignment issue without requiring direct complex inter-layer alignment processes.
Solution Approach 2:
The patent performs preliminary alignment by forming alignment marks in the first layer before depositing the second set of microlenses. This preliminary action establishes a reference framework that guides the subsequent lens formation process, ensuring accurate alignment before the actual microlens structures are created in the second layer.
2Productivity
If misalignment of microlens structures occurs during formation, then the manufacturing process can proceed, but undesired effects such as crosstalk between pixels, reduced incident light conversion efficiency, increased noise, and color shading problems occur
Solution Approach 1:
The patent implements a feedback mechanism where alignment marks are used as reference points to monitor and correct the positioning of microlenses during the formation process. By comparing the actual positions of lenses against the predetermined alignment mark locations, the system can identify and correct misalignment, ensuring high light conversion efficiency and preventing pixel crosstalk.
Solution Approach 2:
The patent replaces direct mechanical alignment methods with an optical/reference-based alignment system using alignment marks. Instead of relying on purely mechanical positioning of lens layers, the system uses optical reference structures that can be precisely detected and used to guide alignment, achieving higher precision in lens positioning.
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 solution effectively minimizes misalignment, enhancing light focusing efficiency, reducing noise, and improving color shading by ensuring accurate alignment of microlenses over image sensing pixels.
Implementation Method 1
The array of lenses may include any number of lenses, where each lens of the array focuses incident light on a respective pixel of the array of imaging pixels
Implementation Method 2
using photolithographic processes, the first group of microlenses are deposited and then melted into their final shape
Data Source
AI summary
An imaging system may include an array of lenses, each of which is aligned over a respective one of a plurality of imaging pixels. The array of lenses may be formed in two layers. The first layer may include a first set of non-adjacent lenses and centering structures between the first lenses. The centering structures may be aligned with the first set of lenses as part of a mask design with a high level of accuracy. The second layer may include a second set of lenses, each of which is formed on a respective one of the centering structures. Forming the second set of lenses may include a reflow process in which surface tension forces center the second set of lenses on their respective centering structures, thereby aligning the second set of lenses with the first set of lenses with a high level of accuracy.