PEALD Metal-Rich Gate Electrode Work Function Control
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Solution Overview
Problem
Current methods for adjusting the work function of metal gate electrodes in semiconductor devices face challenges in achieving precise control over film composition, uniformity, and thickness, while also risking damage to the gate dielectric and substrate materials during oxidizing processes.
Innovation Solution
The method involves using plasma-enhanced atomic layer deposition (PEALD) to selectively adjust plasma parameters, allowing for the precise control of metal-rich metallic-compound film composition by alternately contacting a substrate with spatially and temporally separated vapor phase pulses of metal source chemicals and plasma-excited species, thereby achieving a desired work function for the gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxidizing processes are used to adjust work function, then work function control is achieved, but gate dielectric and substrate materials are damaged
Solution Approach 1:
The patent changes the fundamental parameter of the deposition process from oxidizing conditions to metal-rich metallic compound formation using plasma-enhanced ALD. By controlling plasma parameters (power, pressure, gas composition) and deposition conditions, the work function is adjusted through composition control rather than oxidation, avoiding damage to underlying materials.
Solution Approach 2:
The patent replaces the chemical oxidation mechanism with a physical vapor deposition mechanism (plasma-enhanced ALD). Instead of using oxidizing chemicals that can damage materials, the work function is controlled through precise physical deposition of metal-rich compounds with controlled stoichiometry, substituting a damaging chemical process with a controlled physical process.
2Manufacturing precision
If conventional deposition methods are used, then gate electrode is formed, but precise control over film composition and uniformity is not achieved
Solution Approach 1:
The deposition process is segmented into distinct sequential steps: precursor introduction, plasma treatment, and deposition. This segmentation allows independent optimization of each step, enabling precise control over film composition and uniformity. The plasma parameters and deposition conditions are controlled separately to achieve the desired metal-rich metallic compound with specific stoichiometry.
Solution Approach 2:
The patent implements feedback control through in-situ monitoring of deposition parameters and film properties. Plasma parameters (power, pressure, gas flow) are precisely controlled and adjusted based on real-time measurements, allowing closed-loop control of film composition and uniformity. This feedback mechanism enables achieving target work function values with high precision.
3Measurement precision
If gate electrode composition is adjusted, then work function is controlled, but equivalent oxide thickness increases
Solution Approach 1:
The patent uses metal-rich metallic compounds as composite gate electrode materials, combining metal atoms with controlled stoichiometry to achieve both desired work function and thin film thickness. The composite structure of metal-rich compounds provides the necessary electrical properties while maintaining reduced EOT compared to traditional oxidized metal gates.
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 enables accurate and predictable adjustment of the gate electrode's work function, reducing the thickness of the equivalent oxide thickness (EOT) and enhancing the electrical properties of the gate stack without detrimental effects on the dielectric or substrate materials.
Implementation Method 1
depositing the metallic-compound film by a plasma-enhanced atomic layer deposition (PEALD) process
Implementation Method 2
contacting a substrate in a reaction space with spatially and temporally separated vapor phase pulses of a metal source chemical and plasma-excited species
Data Source
AI summary
Metallic-compound films are formed by plasma-enhanced atomic layer deposition (PEALD). According to preferred methods, film or thin film composition is controlled by selecting plasma parameters to tune the oxidation state of a metal (or plurality of metals) in the film. In some embodiments, plasma parameters are selected to achieve metal-rich metallic-compound films. The metallic-compound films can be components of gate stacks, such as gate electrodes. Plasma parameters can be selected to achieve a gate stack with a predetermined work function.