CMOS Image Sensor Pixel Isolation Structure for FDTI Void Filling
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Solution Overview
Problem
The manufacturing of CMOS image sensors faces challenges with the Front Deep Trench Isolation (FDTI) structure, particularly in filling voids within the pixel isolation pattern, which can lead to particle scratches, physical defects, and changes in product characteristics.
Innovation Solution
The image sensor design includes a substrate with a pixel isolation pattern that features a first pixel isolation filling film with a void, and a second pixel isolation filling film made of insulating material, such as silicon oxide or hafnium oxide, which fills the voids within the FDTI structure, ensuring a thickness less than or equal to the pattern's thickness, and is applied using a method involving etching, polishing, and depositing films to improve the surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Front Deep Trench Isolation (FDTI) structure is used in CMOS image sensor manufacturing, then pixel isolation is improved, but voids form within the pixel isolation pattern causing particles, scratches, and product characteristic changes
Solution Approach 1:
The pixel isolation filling process is divided into multiple stages: first forming an initial filling film, then performing planarization, and finally forming a second filling film to complete the void filling. This segmented approach ensures complete void elimination while maintaining surface flatness and preventing particle contamination.
Solution Approach 2:
Before finalizing the pixel isolation structure, the patent performs preliminary planarization to expose the pixel isolation pattern, then forms a preliminary filling film to address voids. This preliminary action prevents subsequent manufacturing defects by proactively eliminating voids before they cause particles or scratches.
2Manufacturing precision
If the pixel isolation pattern is fully filled to eliminate voids, then manufacturing defects are reduced, but the manufacturing process complexity increases
Solution Approach 1:
The complex filling process is segmented into distinct manageable stages: initial filling film formation, planarization to expose the pattern, and second filling film formation. Each stage has a specific purpose and can be independently optimized, making the overall complex process more controllable and manufacturable.
Solution Approach 2:
The patent changes the physical and chemical parameters of the filling materials at different stages. The first filling film uses specific material properties for initial coverage, while the second filling film uses different parameters to ensure complete void filling and surface planarity, optimizing each stage for its specific function.
3Reliability
If multiple filling films are used to complete void filling, then particle contamination is minimized, but production time increases
Solution Approach 1:
The patent performs preliminary planarization to expose the pixel isolation pattern before forming the filling films. This preliminary action prevents particle contamination by eliminating voids where particles could accumulate, and the planarized surface enables more efficient subsequent processing steps.
Solution Approach 2:
The planarization step serves multiple functions simultaneously: it exposes the pixel isolation pattern for identification, removes excess material that could cause defects, and creates a flat surface for subsequent film deposition. This self-service approach reduces the need for additional separate processing steps.
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 the image sensor's reliability by minimizing defects, improving particle isolation, and maintaining product characteristics, while allowing for efficient manufacturing processes.
Implementation Method 1
a second pixel isolation filling film which fills the voids within the FDTI structure
Implementation Method 2
The pixel isolation pattern includes a first pixel isolation filling film and a second pixel isolation filling film which fills voids within the FDTI structure with an insulating material
Data Source
AI summary
The present disclosure relates to an image sensor and a method of manufacturing thereof, and the image sensor may include: a substrate including a first surface and a second surface opposite the first surface with a thickness therebetween, a plurality of unit pixels including a photoelectric conversion layer within the substrate, a pixel isolation pattern that extends from the second surface of the substrate to the first surface of the substrate within the substrate between the plurality of unit pixels, and a surface insulating film that has flat upper and lower surfaces and is disposed on the plurality of unit pixels of the substrate and the pixel isolation pattern, wherein the pixel isolation pattern includes a first pixel isolation filling film including a first material, a first void, a second pixel isolation filling film including a second material, and a second void, the second pixel isolation filling film extends from the second surface to the first surface, the second void is between the second pixel isolation filling film and the first surface, and the first material and the second material are different from each other.