Stabilizing Material Layer for FET Gate Insulator Metal Penetration
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Solution Overview
Problem
In FET devices, the use of high-k gate dielectrics and metal gates faces challenges in maintaining performance improvements as devices are scaled down, particularly due to issues with threshold voltage control and carrier mobility degradation caused by metal penetration across the high-k portion of the gate insulator, leading to decreased channel mobility and increased carrier scattering.
Innovation Solution
A stabilizing material is introduced into the gate insulator to prevent metal penetration across the high-k portion, using a layered structure with a stabilizing agent layer in direct contact with a threshold modifying cap layer, which contains oxides of metals like La, Mg, Y, Al, Ba, Sr, and Sc, and incorporating Si or Al as stabilizing materials to hinder intermixing and carrier scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high-k gate dielectric is used to reduce equivalent oxide thickness (EOT), then gate dielectric capacitance is improved, but metal penetration across the high-k portion causes threshold voltage control issues and carrier mobility degradation
Solution Approach 1:
A stabilizing material layer is introduced as an intermediary between the high-k gate dielectric and the metal gate electrode. This stabilizing layer acts as a barrier that prevents metal atoms from penetrating into the high-k dielectric, thereby maintaining threshold voltage control while preserving the low EOT benefits of the high-k material.
Solution Approach 2:
The gate dielectric structure is formed as a composite stack comprising multiple materials: the high-k dielectric layer, the stabilizing material layer, and optionally a threshold modifying cap layer. This composite structure combines the advantages of each material - the high-k dielectric provides low EOT, while the stabilizing material prevents metal penetration and maintains reliability.
2Manufacturing precision
If a threshold modifying cap layer is introduced to adjust apparent workfunction, then threshold voltage control is improved, but channel mobility decreases due to metal penetration and carrier scattering
Solution Approach 1:
The stabilizing material layer serves as a protective intermediary positioned between the threshold modifying cap layer and the high-k dielectric. It allows the cap layer to perform its threshold voltage adjustment function while blocking metal atoms from penetrating into the high-k dielectric and causing carrier scattering that would reduce mobility.
Solution Approach 2:
The gate dielectric stack is segmented into distinct functional layers: the threshold modifying cap layer for workfunction adjustment, the stabilizing material layer for preventing metal penetration, and the high-k dielectric layer for capacitance enhancement. This segmentation allows each layer to perform its specific function without interfering with or degrading the performance of other layers.
3Manufacturing precision
If the gate dielectric is made thinner to reduce EOT, then gate dielectric capacitance is improved, but device complexity increases and performance improvements become difficult to maintain
Solution Approach 1:
Instead of simply thinning the gate dielectric, a composite gate dielectric structure is employed that combines high-k dielectric material with a stabilizing material layer. This composite approach achieves low EOT through the high-k material's superior capacitance properties while the stabilizing layer adds necessary functionality for preventing metal penetration, thereby managing complexity through functional integration rather than geometric scaling.
Solution Approach 2:
The invention changes the material parameter (dielectric constant k) rather than relying solely on geometric parameter changes (thickness). By using high-k materials, the system achieves low EOT without proportionally reducing the physical thickness of the gate dielectric stack, thereby avoiding the complexity and reliability issues associated with ultra-thin dielectrics.
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 effectively maintains low equivalent oxide thickness (EOT) and achieves high carrier mobility by preventing metal and Si intermixing, ensuring stable threshold voltage and improved device performance even under high-temperature processing conditions.
Implementation Method 1
The method introduces a stabilizing material into the gate insulator in order to hinder one or more metals from penetrating across the high-k portion of the gate insulator
Implementation Method 2
The dielectric constant of such materials is significantly higher than that of SiO2, which is about 3.9. A high-k material may physically be thicker than oxide, and still have a lower equivalent oxide thickness (EOT) value
Implementation Method 3
Metal gates also assure good conductivity along the width direction of the devices, reducing the danger of possible RC delays in the gate
Data Source
AI summary
A method for fabricating an FET device is disclosed. The FET device has a gate insulator with a high-k dielectric portion, and a threshold modifying material. The method introduces a stabilizing material into the gate insulator in order to hinder one or more metals from the threshold modifying material to penetrate across the high-k portion of the gate insulator. The introduction of the stabilizing material may involve disposing a stabilizing agent over a layer which contains an oxide of the one or more metals. A stabilizing material may also be incorporated into the high-k dielectric. Application of the method may lead to FET devices with unique gate insulator structures.