CMOS Image Sensor Microlens Bridge Prevention via Segmentation
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Solution Overview
Problem
Conventional CMOS image sensors with microlenses suffer from a 'bridge phenomenon' during the thermal flow process, leading to poor photosensitivity and optical properties due to overflowed substances collecting between adjacent microlenses, and non-uniform alignment of dome-typed microlenses.
Innovation Solution
The method involves forming openings between microlenses using a binary mask, negative photoresist, or phase-shifted mask to pattern an over-coating layer, preventing bridge formation and allowing for larger microlenses without increasing manufacturing costs, by collecting overflowed substances in these openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microlenses are formed using conventional methods without openings, then the manufacturing process is simpler, but bridge phenomenon occurs between adjacent microlenses during thermal flow process leading to poor photosensitivity
Solution Approach 1:
The patent introduces openings between adjacent microlenses by patterning the over-coating layer, which segments the continuous microlens structure. This segmentation prevents the bridge phenomenon where overflowed substances would otherwise connect adjacent microlenses during thermal flow, thereby improving photosensitivity while maintaining manufacturing feasibility
Solution Approach 2:
The patent performs preliminary patterning of the over-coating layer to create openings before forming the microlenses. This preliminary action ensures that when thermal flow occurs and substances overflow, they are collected in the pre-formed openings rather than forming bridges between microlenses, thus preventing the bridge phenomenon before it can occur
2Reliability
If larger microlenses are formed to increase light collection, then photosensitivity improves, but manufacturing complications arise due to bridge phenomenon
Solution Approach 1:
By introducing openings between larger microlenses, the patent segments the microlens array structure to prevent bridge formation. This allows larger microlenses to be manufactured without the complications of bridge phenomenon, thereby achieving improved photosensitivity through larger light-collecting elements
Solution Approach 2:
The openings act as intermediary spaces that collect overflowed substances during thermal flow. These intermediary regions prevent direct connection (bridge formation) between adjacent larger microlenses, enabling the manufacturing of larger microlenses without the usual complications
3Reliability
If dome-typed microlenses are formed without openings, then the process is simpler, but non-uniform alignment occurs leading to poor optical properties
Solution Approach 1:
The patent performs preliminary patterning of the over-coating layer to create openings before dome formation. This preliminary structure provides alignment references that guide the thermal flow process, ensuring uniform alignment of dome-typed microlenses and improving optical properties
Solution Approach 2:
The openings segment the over-coating layer structure, creating defined regions that control the thermal flow and dome formation process. This segmentation ensures uniform alignment of adjacent domes by preventing uncontrolled material flow between them, thereby improving optical properties
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 enhances photosensitivity and optical properties by preventing bridge phenomena and ensuring uniform microlens alignment, allowing for wider microlenses without manufacturing complications, thereby improving light concentration on photodiodes.
Implementation Method 1
forming openings between the microlenses by patterning the over-coating layer
Implementation Method 2
during the thermal flow process, leading to poor photosensitivity and optical properties due to overflowed substances collecting between adjacent microlenses
Data Source
AI summary
The method for manufacturing a CMOS image sensor is employed to prevent bridge phenomenon between adjacent microlenses by employing openings between the microlenses. The method includes the steps of: preparing a semiconductor substrate including isolation regions and photodiodes therein obtained by a predetermined process; forming an interlayer dielectric (ILD), metal interconnections and a passivation layer formed on the semiconductor substrate in sequence; forming a color filter array having a plurality of color filters on the passivation layer; forming an over-coating layer (OCL) on the color filter array by using a positive photoresist or a negative photoresist; forming openings in the OCL by patterning the OCL by using a predetermined mask; and forming dome-typed microlenses on a patterned OCL.