Nanosheet FET Gate Liner for Threshold Voltage Uniformity
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Solution Overview
Problem
As semiconductor devices undergo miniaturization, non-uniform thickness of work function material leads to threshold voltage variations in nanosheet field-effect transistors, and the diffusion of aluminum from the work function material into other layers poses additional challenges.
Innovation Solution
A liner material is formed around the work function material to prevent merging between adjacent nanosheets and reduce aluminum diffusion, ensuring uniform thickness and stability of the work function layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the minimum feature size is reduced to improve integration density, then more components can be integrated into a given area, but non-uniform thickness of work function material leads to threshold voltage variations
Solution Approach 1:
A liner material layer is introduced as an intermediary between the work function material and adjacent structures. This liner material prevents unwanted merging of work function material from adjacent nanosheets while allowing the work function material to maintain its intended thickness and electrical properties, thereby resolving the threshold voltage uniformity issue that arises during miniaturization
Solution Approach 2:
The gate structure is segmented into distinct functional layers: the work function material layer and the liner material layer. This segmentation allows each layer to perform its specific function independently - the work function material provides the necessary electrical work function while the liner material provides physical separation and thickness control, enabling precise control over threshold voltage even as feature sizes are reduced
2Length of moving object
If the work function material thickness is reduced to enable further miniaturization, then smaller device dimensions are achieved, but aluminum diffusion into other layers increases
Solution Approach 1:
The liner material serves as a diffusion barrier intermediary between the aluminum-containing work function material and adjacent layers. This intermediate layer physically blocks aluminum atoms from diffusing into surrounding structures, eliminating the harmful diffusion effect while allowing the device dimensions to be reduced as needed
Solution Approach 2:
The problematic aluminum diffusion component is effectively extracted or isolated from the system by introducing the liner material barrier. This separates the work function material's electrical function from its harmful diffusion property, allowing miniaturization to proceed without the aluminum diffusion issue
Data Source
AI summary
A semiconductor device includes: a fin protruding above a substrate; source/drain regions over the fin; nanosheets between the source/drain regions; and a gate structure over the fin and between the source/drain regions, the gate structure including: a gate dielectric material around each of the nanosheets; a work function material around the gate dielectric material; a liner material around the work function material, where the liner material has a non-uniform thickness and is thicker at a first location between the nanosheets than at a second location along sidewalls of the nanosheets; and a gate electrode material around at least portions of the liner material.