Dual-Layer Gate Dielectric for Threshold Voltage Tuning
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in maintaining integration density and tuning threshold voltage while maintaining high-k characteristics in gate dielectric structures, which are crucial for efficient transistor performance.
Innovation Solution
A semiconductor device with a gate dielectric structure comprising a thin first dielectric layer that creates dipoles to tune the threshold voltage, combined with a thick high-k second dielectric layer, allowing for high-k characteristics similar to the second layer, is developed. This structure includes an interfacial layer, a first dielectric layer formed by atomic layer deposition, and a second dielectric layer with a higher oxygen areal density, enabling effective threshold voltage tuning without significantly increasing capacitance equivalent thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thin first dielectric layer is used to tune threshold voltage, then threshold voltage tuning capability is improved, but capacitance equivalent thickness increases
Solution Approach 1:
The gate dielectric structure uses a composite of two dielectric layers with different properties. The first dielectric layer (higher oxygen areal density) provides threshold voltage tuning capability, while the second dielectric layer (lower oxygen areal density, thicker) maintains high-k characteristics. This composite structure allows both functions to coexist without compromising overall device performance.
Solution Approach 2:
Different regions of the gate dielectric structure have different oxygen areal densities tailored for specific functions. The first dielectric layer has higher oxygen areal density optimized for threshold voltage control, while the second layer has lower oxygen areal density optimized for maintaining high-k characteristics. Each layer's local properties are optimized for its specific role in the overall structure.
2Productivity
If feature size is reduced to increase integration density, then integration density is improved, but maintaining high-k characteristics and threshold voltage tuning becomes more difficult
Solution Approach 1:
The dual-layer gate dielectric structure with distinct oxygen areal densities enables simultaneous achievement of threshold voltage tuning and high-k characteristics even as feature sizes shrink. This composite approach provides the design flexibility needed to maintain performance at smaller dimensions.
Solution Approach 2:
The invention changes the oxygen areal density parameter across different layers to achieve different functional outcomes. By varying this fundamental material parameter, the structure can simultaneously provide threshold voltage tuning capability and maintain high-k characteristics, enabling continued scaling while preserving device performance.
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 solution allows for precise tuning of threshold voltage and maintains high-k characteristics, enhancing the performance of nanostructure-FETs by optimizing the gate dielectric structure, thereby addressing the challenges of shrinking feature sizes and integration density.
Implementation Method 1
a first dielectric layer that creates dipoles in the gate dielectric structure to tune the threshold voltage
Data Source
AI summary
A semiconductor device is provided in accordance with some embodiments. The semiconductor device includes an interfacial layer disposed over a channel region, a gate dielectric structure disposed over the channel region, and a gate electrode disposed over the gate dielectric structure. The gate dielectric structure includes a first layer of an oxide of a first metal disposed over the interfacial layer and a second layer of an oxide or silicate of a second metal disposed over the first layer. The first layer has a first thickness, and the second layer has second thickness that is at least three times greater than the first thickness. An oxygen areal density of the oxide of the first metal is greater than an oxygen areal density of the oxide of the second metal.