Gate Dielectric Nitrogen Incorporation via CVD
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Solution Overview
Problem
The challenge in semiconductor technology is to enhance the nitrogen content in gate dielectric layers without degrading the electrical properties, as conventional methods like decoupled plasma nitridation can lead to nitrogen distribution near the substrate, affecting channel performance.
Innovation Solution
A method involving the deposition of a silicon nitride layer using a nitrogen-containing gas and a silicon-containing gas in a furnace, with optional soft and thermal annealing processes, to achieve a high nitrogen content without plasma, ensuring improved interface and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If decoupled plasma nitridation is used to increase nitrogen content in gate dielectric layer, then nitrogen content is improved, but nitrogen distributes near substrate causing channel performance degradation
Solution Approach 1:
The patent changes the fundamental parameter of nitrogen introduction method from plasma-based to chemical vapor deposition (CVD) using nitrogen-containing gases (such as ammonia or nitrogen gas). This parameter change allows nitrogen to be incorporated into the gate dielectric layer during the deposition process itself, rather than through subsequent plasma treatment, thereby achieving high nitrogen content without the harmful near-substrate distribution that plagues plasma methods
Solution Approach 2:
The patent introduces nitrogen-containing gases (ammonia or nitrogen gas) as intermediaries to deliver nitrogen to the gate dielectric layer during CVD deposition. These intermediary gases enable controlled nitrogen incorporation through chemical reactions in the vapor phase, avoiding the direct plasma exposure that causes nitrogen to concentrate near the substrate and degrade channel performance
2Speed
If gate dielectric layer thickness is reduced to improve device speed, then operating speed is improved, but leakage current increases
Solution Approach 1:
The patent creates a composite gate dielectric structure consisting of silicon oxide combined with nitrogen-containing species (forming SiON-like characteristics). This composite material approach allows the gate dielectric to maintain thin dimensions for high-speed operation while the nitrogen incorporation provides enhanced electrical properties that suppress leakage current, effectively combining the benefits of thin thickness with high electrical integrity
Solution Approach 2:
The patent changes the compositional parameter of the gate dielectric layer by incorporating nitrogen during CVD deposition. This parameter change transforms the material properties of the gate dielectric, enabling it to function effectively at reduced thicknesses by improving its electrical characteristics and reducing intrinsic leakage mechanisms that would otherwise dominate in ultra-thin structures
3Quantity of substance
If plasma power or processing time is increased to enrich nitrogen content, then nitrogen content is improved, but nitrogen distributes near substrate impacting channel performance
Solution Approach 1:
The patent replaces the plasma-based nitrogen introduction mechanism with a chemical vapor deposition mechanism. Instead of using plasma physics (electromagnetic fields, ion bombardment, and radical reactions), the patent employs chemical reactions between nitrogen-containing gases and silicon species in the vapor phase. This substitution provides superior control over nitrogen distribution, as CVD processes inherently offer more uniform deposition and less tendency for near-substrate concentration compared to plasma methods
Solution Approach 2:
The patent uses nitrogen-containing gases as intermediary carriers to deliver nitrogen atoms to the growing film during CVD. These intermediary molecules (such as NH3 or N2) provide controlled, gradual nitrogen incorporation through thermal decomposition and chemical reaction, enabling precise spatial and temporal control over nitrogen distribution that avoids the uncontrolled near-substrate accumulation characteristic of plasma-based approaches
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 results in a gate dielectric layer with enhanced nitrogen content, higher dielectric constant, and controlled equivalent oxide thickness, reducing leakage current and maintaining desirable electrical performance.
Implementation Method 1
depositing a silicon nitride layer on the substrate by simultaneously introducing a nitrogen-containing gas and a silicon-containing gas
Implementation Method 2
performing a soft annealing process before depositing the silicon nitride layer but after forming the silicon oxide layer. This soft annealing process is, for example, performed using the nitrogen-containing gas
Implementation Method 3
performing a thermal annealing process after depositing the silicon nitride layer but before forming the gate. The thermal annealing process may be performed at a temperature of 600° C. to 800° C.
Data Source
AI summary
A gate structure and a method for fabricating the same are described. A substrate is provided, and a gate dielectric layer is formed on the substrate. The formation of the gate dielectric layer includes depositing a silicon nitride layer on the substrate by simultaneously introducing a nitrogen-containing gas and a silicon-containing gas. A gate is formed on the gate dielectric layer, so as to form the gate structure.