Image Sensor Through-Via Structure for Leakage Current Isolation
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Solution Overview
Problem
Image sensors using the TSV or BVS method often experience leakage current issues due to defects in the isolation structure between terminals, which affect image quality.
Innovation Solution
An image sensor design that includes a semiconductor substrate with a pixel isolation structure, an anti-reflection layer of TiO2, and a through via structure with a conductive layer on the inner wall, where the first conductive layer has a higher work function than Ti and the second conductive layer is made of tungsten, to reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through via structure is formed to connect pixels and logic regions, then electrical connection is achieved, but leakage current occurs at the interface with anti-reflection layer
Solution Approach 1:
The first conductive layer acts as an intermediary between the through via structure and the anti-reflection layer. This intermediate layer with higher work function than Ti creates a potential barrier that prevents direct leakage current flow between the conductive via and the anti-reflection layer, while still allowing the necessary electrical connection to be maintained through the second conductive layer.
Solution Approach 2:
The patent changes the work function parameter of the conductive layer at the critical interface. By selecting a material with higher work function than Ti for the first conductive layer, the energy barrier for electron flow is increased, thereby reducing leakage current. This parameter modification is applied specifically at the interface region where leakage occurs, while maintaining overall electrical connectivity through the tungsten layer.
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 design effectively reduces leakage current and improves image quality by enhancing the isolation between pixels and logic regions, while also improving sensitivity to blue light and reliability.
Implementation Method 1
the first conductive layer includes a material having a higher work function than Ti
Implementation Method 2
the anti-reflection layer includes TiO2
Data Source
AI summary
Provided is an image sensor including a semiconductor substrate including a first pixel and a second pixel adjacent to the first pixel, a pixel isolation structure between the first pixel and the second pixel, an anti-reflection layer on the first pixel, the second pixel, and the pixel isolation structure, and a through via structure in a through via hole that is in the anti-reflection layer and the semiconductor substrate. The through via structure may include a first conductive layer on an inner wall of the through via hole, and a second conductive layer on the first conductive layer on the inner wall of the through via hole, and the anti-reflection layer may include TiO2, and the first conductive layer may include a material having a higher work function than Ti.