Fluorine Passivation Layer for CMOS Image Sensor Gate Insulating Layer
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Solution Overview
Problem
Current image sensors face challenges in achieving optimal structural quality due to defects in the gate insulating layer, particularly with the inefficient diffusion of fluorine, which affects the performance of CMOS image sensors.
Innovation Solution
Incorporating a first passivation layer containing fluorine between the gate insulating layer and the gate electrode, with a heat treatment process to diffuse fluorine into the gate insulating layer, ensuring a higher concentration of fluorine in the gate insulating layer compared to the gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate insulating layer structure is used without fluorine passivation, then the device structure is simpler and manufacturing is easier, but the gate insulating layer contains defects that degrade image sensor performance
Solution Approach 1:
A first passivation layer containing fluorine is formed on the gate insulating layer before the gate electrode is deposited. This preliminary fluorine incorporation prepares the gate insulating layer to compensate for defects that will exist after subsequent manufacturing steps, thereby improving reliability before the device is fully assembled
Solution Approach 2:
The first passivation layer acts as an intermediary between the gate insulating layer and the gate electrode. It provides fluorine atoms that diffuse into the gate insulating layer to compensate for defects, serving as a mediator that improves the quality of the gate insulating layer without requiring direct modification of the gate electrode or substrate
2Manufacturing precision
If fluorine is incorporated into the gate insulating layer to compensate defects, then the structural quality improves, but additional manufacturing steps and process complexity are required
Solution Approach 1:
The formation of the first passivation layer is merged with the existing manufacturing sequence by positioning it between the gate insulating layer formation and the gate electrode deposition. The fluorine-containing material is deposited using standard thin-film deposition techniques, and subsequent heat treatment merges the fluorine diffusion process with other thermal processing steps already required in CMOS fabrication
Solution Approach 2:
The fluorine concentration in the first passivation layer and the heat treatment temperature are optimized to achieve effective defect compensation. By controlling these parameters, the process achieves high manufacturing precision in gate insulating layer quality while keeping the additional process steps manageable within existing fabrication capabilities
3Reliability
If fluorine concentration in the gate insulating layer is increased to compensate defects, then device performance improves, but fluorine may also accumulate in the gate electrode causing potential degradation
Solution Approach 1:
The first passivation layer is positioned specifically between the gate insulating layer and the gate electrode, creating a localized fluorine source. This local quality approach ensures that fluorine atoms primarily diffuse into the gate insulating layer where they are needed for defect compensation, while the gate electrode remains protected from excessive fluorine accumulation by being separated by the passivation layer structure
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 structural quality of the image sensor by effectively compensating defects in the gate insulating layer, improving the overall performance and efficiency of the CMOS image sensor.
Implementation Method 1
A heat treatment or annealing process is performed to diffuse fluorine in the first passivation layer
Data Source
AI summary
An image device includes a first active region and a second active region disposed on a substrate. Each of the first active region and the second active region includes a gate insulating layer disposed on the substrate and a gate electrode disposed on the gate insulating layer. At least one of the first active region and the second active region further includes a first passivation layer containing fluorine (F) disposed between the gate insulating layer and the gate electrode. A concentration of fluorine in the gate insulating layer is higher than a concentration of fluorine in the gate electrode.