Gate Electrode Work Function Stack for Precise Threshold Tuning
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Solution Overview
Problem
As semiconductor devices continue to integrate more components into a given area through reduced minimum feature sizes, challenges arise in accurately tuning threshold voltages and maintaining device performance.
Innovation Solution
The formation of gate electrodes with multiple work function tuning layers, where a barrier layer inhibits modification of underlying layers during treatment, allowing for precise tuning of threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple work function tuning layers are formed with different materials, then threshold voltage tuning precision is improved, but device structure complexity increases
Solution Approach 1:
The gate electrode is segmented into multiple distinct layers including a first work function tuning layer with a first material, a second work function tuning layer with a second material, and optionally a third work function tuning layer with a third material. Each layer can be independently tuned to achieve precise threshold voltage control without requiring the entire gate structure to be redesigned.
Solution Approach 2:
The gate electrode employs composite material construction by combining multiple work function tuning layers with different materials (e.g., titanium nitride, tantalum nitride, tungsten silicide, cobalt silicide) and dielectric materials. This composite structure enables fine-grained adjustment of threshold voltage while maintaining overall gate functionality.
2Productivity
If minimum feature sizes are reduced to increase integration density, then component integration density is improved, but manufacturing precision requirements increase
Solution Approach 1:
Different regions of the gate electrode structure have different material compositions and properties tailored to specific functions. The work function tuning layers are positioned and dimensioned locally to achieve the desired threshold voltage characteristics for each transistor, allowing precise control even at reduced feature sizes.
Solution Approach 2:
The threshold voltage is tuned by changing material parameters such as work function, layer thickness, and material composition rather than relying solely on geometric scaling. This allows integration density to increase through scaling while maintaining manufacturing precision through material property control.
Data Source
AI summary
In an embodiment, a device includes: a channel region; a gate dielectric layer on the channel region; a first work function tuning layer on the gate dielectric layer, the first work function tuning layer including a n-type work function metal; a barrier layer on the first work function tuning layer; a second work function tuning layer on the barrier layer, the second work function tuning layer including a p-type work function metal, the p-type work function metal different from the n-type work function metal; and a fill layer on the second work function tuning layer.