Composite Dielectric Structure for Leakage Reduction
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Solution Overview
Problem
The reduction in transistor gate electrode length and memory cell size in semiconductor devices leads to increased leakage current, impurity infiltration, and decreased threshold voltage due to thin gate insulation layers, and reduced capacitor capacitance, affecting data readability and device stability.
Innovation Solution
A composite dielectric structure is formed by a first dielectric layer with a high dielectric constant and a second dielectric layer created through plasma nitrification of a silicon-based preliminary layer, which reduces nitrogen density at the interface and enhances carrier mobility, while maintaining a high dielectric constant and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the gate insulation layer thickness is reduced to accommodate smaller transistor gate electrode lengths, then device integration density is improved, but leakage current increases and threshold voltage decreases due to electron tunneling and impurity infiltration
Solution Approach 1:
The patent applies composite materials by forming a gate insulation layer with multiple dielectric layers including a first dielectric layer (e.g., hafnium oxide, tantalum oxide, or strontium titanate) and a second dielectric layer (e.g., silicon oxide or silicon oxynitride). This composite structure achieves both high dielectric constant for capacitance and appropriate thickness for leakage prevention, resolving the contradiction between integration density and reliability.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different regions of the gate insulation layer. The first dielectric layer provides high dielectric constant for capacitance enhancement, while the second dielectric layer provides low defect density and appropriate barrier properties. This localized functional differentiation allows the structure to simultaneously achieve high integration density and low leakage current.
2Reliability
If high dielectric constant materials such as hafnium oxide are used in the gate insulation layer, then capacitor capacitance is improved, but the material becomes crystallized during heat treatment causing increased leakage current and decreased threshold voltage
Solution Approach 1:
The patent applies the intermediary principle by introducing a second dielectric layer (silicon oxide or silicon oxynitride) as a protective barrier between the high dielectric constant material and the environment. This intermediary layer prevents crystallization of the first dielectric layer during heat treatment while maintaining the high capacitance properties, thus resolving the contradiction between capacitance enhancement and compositional stability.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the deposition conditions, thickness ratios, and heat treatment parameters of the composite dielectric structure. By optimizing these parameters, the high dielectric constant material maintains its amorphous state during processing while still providing the desired capacitance enhancement, resolving the contradiction between capacitance and crystallization resistance.
3Reliability
If nitrogen is introduced into the gate insulation layer through plasma nitrification, then carrier mobility is improved, but nitrogen may accumulate at interfaces causing increased defect density
Solution Approach 1:
The patent applies local quality by selectively introducing nitrogen into specific regions of the dielectric structure through plasma nitrification. The nitrogen is concentrated in the second dielectric layer where it enhances carrier mobility, while the first dielectric layer and critical interfaces are protected from excessive nitrogen accumulation. This localized nitrogen introduction resolves the contradiction between mobility enhancement and defect reduction.
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 composite dielectric structure decreases leakage current, reduces impurities, and improves carrier mobility, achieving a thin equivalent oxide thickness with a thicker physical thickness, thereby enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
A plasma nitrification treatment is performed on the preliminary dielectric layer to change it into a second dielectric layer
Data Source
AI summary
Some methods that are provided form a composite dielectric structure on a substrate. A first dielectric layer that includes metal and oxygen is formed on a substrate. A preliminary dielectric layer that includes silicon is formed on the first dielectric layer. A plasma nitriding treatment is performed on the preliminary dielectric layer to change it into a second dielectric layer. The composite dielectric structure includes the second dielectric layer and the first dielectric layer. Other methods form a semiconductor device that includes the composite dielectric structure.