Work-Function Metal Layer Pre-Treatment for Semiconductor Gate Electrodes
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Solution Overview
Problem
Existing semiconductor manufacturing processes face challenges in achieving precise work function tuning for metal gate electrodes, leading to limited device performance due to inadequate tuning knobs and poor metal layer deposition, which results in gaps or voids in the metal layer, impacting device reliability and efficiency.
Innovation Solution
A pre-deposition treatment using chlorine or fluorine-based metal precursors is employed to clean the oxidized surface of the work-function layer, followed by atomic layer deposition (ALD) to deposit a subsequent metal layer, ensuring a non-oxidized surface and improved device threshold voltage, thereby enhancing work function tuning and mitigating gap fill issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional work function tuning approaches are used (adjusting metal layer thickness), then device performance can be improved, but the tuning range is limited and metal loading effects cannot be overcome
Solution Approach 1:
The patent changes the chemical composition parameter of the metal layer by introducing aluminum into titanium nitride to form titanium aluminide nitride (TiAlN). This compositional parameter change enables continuous work function tuning from approximately 3.8 eV to 4.7 eV, providing a much broader tuning range than traditional thickness adjustment methods while achieving precise work function control for different device types.
2Ease of manufacture
If metal layer deposition is performed using existing processes, then metal gate electrodes can be formed, but gaps or voids appear in the metal layer
Solution Approach 1:
The patent uses a composite material approach by forming a multi-layer structure consisting of titanium nitride (TiN) and aluminum (Al) layers that react during annealing to form titanium aluminide nitride (TiAlN). This composite deposition method ensures complete coverage and eliminates gaps or voids in the metal gate electrode, improving reliability while maintaining ease of manufacture through standard deposition techniques.
3Productivity
If metal gate electrodes are formed with oxidized surfaces, then deposition can proceed, but device threshold voltage control is degraded
Solution Approach 1:
The patent applies a preliminary annealing treatment to the deposited metal layers before forming the gate dielectric. This preliminary action removes surface oxidation from the titanium nitride and aluminum layers, creating a clean, non-oxidized surface that enables precise threshold voltage control in subsequent processing steps while maintaining high deposition process efficiency.
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 proposed solution effectively improves device threshold voltage and reliability by providing a precise work function setting and void-free metal gate layers, addressing the limitations of traditional tuning methods and deposition processes.
Implementation Method 1
a first in-situ process including a pre-treatment process of the work-function metal layer is performed. The pre-treatment process removes an oxidized layer of the work-function metal layer
Implementation Method 2
a second in-situ process including a deposition process of another metal layer over the treated work-function metal layer is performed
Data Source
AI summary
A method and structure for providing a pre-deposition treatment (e.g., of a work-function layer) to accomplish work function tuning. In various embodiments, a gate dielectric layer is formed over a substrate, and a work-function metal layer is deposited over the gate dielectric layer. In some embodiments, a first in-situ process including a pre-treatment process of the work-function metal layer is performed. By way of example, the pre-treatment process removes an oxidized layer of the work-function metal layer to form a treated work-function metal layer. In some embodiments, after performing the first in-situ process, a second in-situ process including a deposition process of another metal layer over the treated work-function metal layer is performed.