Backside-illuminated CMOS Image Sensor Metal Grid and Deep Trench Isolation
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Solution Overview
Problem
The manufacturing process for backside-illuminated CMOS image sensors is complex, time-consuming, and costly due to the need for high precision alignment between Deep Trench Isolation (DTI) and Metal grid processes, which also results in reduced yield and increased optical and electrical signal crosstalk.
Innovation Solution
A one-step method is introduced where grid-shaped deep trenches are formed on the back of a silicon substrate, filled with metal, and combined with an insulating layer to create a composite structure that acts as both a metal grid and deep trench isolation, reducing the need for separate DTI and Metal grid processes and improving material utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate DTI process and Metal grid process are used to prevent optical and electrical signal crosstalk, then signal isolation performance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines the DTI process and Metal grid process into a single integrated process. The metal grid is formed within the deep trench isolation structure during the same manufacturing steps, eliminating the need for separate processes while maintaining both signal isolation and grid functionality
Solution Approach 2:
The deep trench isolation structure is designed to serve multiple functions simultaneously: it provides electrical isolation between pixels, serves as the substrate for the metal grid formation, and contributes to optical signal isolation. This multi-functional design reduces overall device complexity
2Reliability
If high precision alignment between DTI process and Metal grid process is implemented, then signal isolation effectiveness is improved, but manufacturing time and cost increase
Solution Approach 1:
By merging the alignment requirements into a single process, the patent eliminates the need for multiple high-precision alignment operations. The metal grid and DTI structure are formed concurrently with inherent alignment, reducing both time and complexity
3Reliability
If separate DTI process and Metal grid process are used, then signal isolation is achieved, but productivity decreases
Solution Approach 1:
The integration of DTI and metal grid processes into one manufacturing flow reduces the total number of process steps, eliminates intermediate handling and alignment operations, and thereby increases production efficiency and productivity
4Ease of manufacture
If conventional frontside-illuminated structure is used, then manufacturing process is simpler, but light sensitivity performance deteriorates
Solution Approach 1:
The patent inverts the conventional frontside-illuminated structure to a backside-illuminated structure, where light enters through the back of the substrate. This inversion allows the photodiode active region to be directly exposed to incident light without passing through metal interconnects and other frontside structures, significantly improving light sensitivity while the integrated DTI-grid process maintains manufacturing simplicity
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 simplifies the manufacturing process, reduces costs, and enhances production efficiency by eliminating the need for high precision alignment, while improving the photosensitive effect by placing the photosensitive area closer to the incident light plane.
Implementation Method 1
the insulating layer is deposited on the inner wall surface of the deep trenchs by CVD or ALD
Implementation Method 2
the insulating layer is deposited on the inner wall surface of the deep trenchs by CVD or ALD
Implementation Method 3
the diffusion barrier layer is formed on the surface of the insulating layer by CVD, PVD, ALD, or sputtering
Implementation Method 4
the diffusion barrier layer is formed on the surface of the insulating layer by CVD, PVD, ALD, or sputtering
Implementation Method 5
the diffusion barrier layer is formed on the surface of the insulating layer by CVD, PVD, ALD, or sputtering
Implementation Method 6
filling the metal W in the deep trenchs by CVD or PVD
Implementation Method 7
filling the metal W in the deep trenchs by CVD or PVD
Data Source
AI summary
The present disclosure discloses a method for manufacturing a backside-illuminated CMOS image sensor structure, the method comprises: providing a silicon substrate which has been subjected to a frontside processing and a back thinning; forming grid-shaped deep trenchs on the back of the silicon substrate; forming an insulating layer on the inner wall surface of the deep trenchs to form a grid-shaped deep trenchs isolation structure; forming a diffusion barrier layer on the surface of the insulating layer; filling metal in the deep trenchs to form a grid-shaped composite structure in which the Metal grid is combined with the deep trenchs isolation structure.