Shallow Trench Isolation Plasma Treatment
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Solution Overview
Problem
Conventional shallow trench isolation (STI) methods fail to provide adequate electrical isolation, particularly for high-voltage devices, as the breakdown voltage often falls below the required 7 volts, impacting device performance and yield.
Innovation Solution
The method involves forming a trench in a substrate, depositing a liner oxide layer, treating it in a plasma environment with fluorine-containing gases to trap charges, and filling the trench with a dielectric material, with optional ion implantation to enhance breakdown voltage, thereby improving isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional STI methods are used (etching trenches, overfilling with dielectric, and removing excess), then the manufacturing process is simple and well-established, but the breakdown voltage is insufficient (below 7V) for high-voltage devices
Solution Approach 1:
The patent applies preliminary action by forming a liner oxide layer on the trench sidewalls before filling with dielectric material. This preparatory step modifies the trench surface to improve charge trapping and enhance breakdown voltage. The liner oxide is deposited conformally on the trench walls, creating a functional interface that prevents charge accumulation at the silicon-dielectric interface, thereby resolving the breakdown voltage insufficiency without fundamentally changing the overall STI process flow
Solution Approach 2:
The patent employs parameter changes by introducing fluorine-containing gases during plasma treatment of the liner oxide layer. This chemical modification changes the electrical properties of the oxide, enhancing its charge trapping capability. The plasma treatment alters the oxide's composition and structure, creating a region with improved electrical characteristics that directly addresses the breakdown voltage requirement while maintaining process compatibility
2Reliability
If the trench is filled with dielectric material to provide isolation, then electrical isolation is achieved, but charge accumulation at the interface reduces breakdown voltage
Solution Approach 1:
The patent uses the liner oxide layer as an intermediary between the silicon substrate and the dielectric fill material. This intermediate layer serves as a buffer zone that traps charges away from the critical silicon-dielectric interface. The liner oxide mediates the interaction between silicon and dielectric, preventing direct charge accumulation at the interface and thereby maintaining high breakdown voltage while preserving electrical isolation functionality
Solution Approach 2:
The patent converts the potentially harmful effect of charge accumulation into a beneficial feature by using plasma treatment with fluorine-containing gases. The plasma process intentionally introduces charges into the liner oxide layer, but these charges are trapped within the oxide rather than accumulating at the interface. The harmful charge accumulation is thus transformed into a controlled charge distribution that enhances breakdown voltage through the modified oxide's electrical properties
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 significantly increases the breakdown voltage of STIs, ensuring improved electrical isolation and meeting the requirements for high-voltage devices, thus enhancing device performance and yield.
Implementation Method 1
treating it in a plasma environment with fluorine-containing gases to trap charges
Implementation Method 2
optional ion implantation to enhance breakdown voltage
Implementation Method 3
overfilling the trenches with a dielectric such as an oxide
Data Source
AI summary
An embodiment of the disclosure includes a method of forming a shallow trench isolation structure. A substrate is provided. The substrate includes a top surface. A trench is formed extending from the top surface into the substrate. The trench has sidewalls and a bottom surface. A liner oxide layer is formed on the sidewalls and the bottom surface. The liner oxide layer is treated in a plasma environment comprises at least one of NF3, F2, and BF2. The trench is filled with a dielectric layer.