Deep Trench Isolation Biasing for Leakage Control in CMOS Sensors
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Solution Overview
Problem
Deep trench isolation (DTI) structures in semiconductor integrated circuits face challenges in preventing leakage as device dimensions decrease, requiring improved design and manufacturing processes to maintain electrical and optical isolation effectively.
Innovation Solution
The method involves forming a DTI structure with a p-type semiconductor isolation layer and connection features, where the isolation layer forms a junction with the semiconductor substrate, and applying a reverse bias to enhance the electric field and physical passivation, allowing for controllable passivation without the need for deep doped p-wells, thus simplifying the manufacturing process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DTI structures are used, then electrical and optical isolation is provided, but leakage prevention becomes difficult as device dimension decreases
Solution Approach 1:
The patent changes the physical and chemical parameters of the isolation layer by introducing a graded doping concentration profile (from heavily doped at the interface to lightly doped deeper in the substrate) and selecting specific material compositions (such as silicon oxide with varying oxygen content or silicon nitride with different nitrogen ratios). These parameter changes enable the isolation structure to maintain effective electrical and optical isolation even as device dimensions shrink, preventing leakage without requiring proportionally deeper isolation structures.
2Reliability
If deep doped p-wells are used to enhance passivation, then leakage is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for deep doped p-wells by replacing them with a specially designed isolation layer structure. The isolation layer alone, with its graded doping profile and optimized material properties, provides sufficient passivation and leakage prevention. This extraction simplifies the manufacturing process by removing the complex steps required to form, dope, and anneal deep p-wells, while maintaining or improving passivation quality.
Solution Approach 2:
The isolation layer is designed to perform multiple functions simultaneously: it provides electrical isolation, optical isolation, and passivation without requiring separate deep p-well structures. This multi-functionality reduces overall device complexity and streamlines the manufacturing process while achieving the same or better reliability performance.
3Productivity
If device dimension is reduced, then integration density increases, but leakage through isolation structures increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration profile within the isolation layer, with higher doping concentrations near the semiconductor substrate interface and gradually lower concentrations deeper in the isolation layer. This localized variation in doping quality provides strong field effect passivation at the critical interface region where leakage occurs, while maintaining adequate isolation properties throughout the structure. This enables effective leakage prevention in high-density integrated devices without requiring uniform deep isolation.
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 enables effective isolation and reduced leakage, allowing for smaller device dimensions and lower manufacturing costs, with enhanced passivation capabilities compatible with various semiconductor materials, and is applicable to both Backside Illumination and Front Side Illumination CMOS image sensors.
Implementation Method 1
applying a reverse bias to enhance the electric field and physical passivation
Implementation Method 2
enhance the electric field and physical passivation
Data Source
AI summary
A Deep Trench Isolation (DTI) structure is disclosed. A DTI structure formed in a semiconductor substrate. The DIT structure includes an isolation layer and filling material. The isolation layer is formed from a p-type semiconductor material. Sidewall portions of the isolation layer are in contact with the semiconductor substrate. A bottom portion of the isolation layer is in contact with a connection feature, which is connected to an interconnect structure and configured to apply a bias to the isolation layer of the DTI structure to achieve a controllable passivation in the semiconductor substrate.