Nanosheet Gate Cut Layout for Precise Work Function Metal Patterning
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Solution Overview
Problem
The challenge in nanosheet device fabrication is the difficulty in patterning work function metal (WFM) and achieving accurate gate cuts, particularly as feature sizes decrease, leading to issues such as overetching and damage to the WFM.
Innovation Solution
The proposed solution involves building first and second nanosheet devices with a dielectric bar located between them. In the first nanosheet device, a first WFM is formed, while in the second nanosheet device, a second WFM extends across the dielectric bar and the first WFM, thereby improving WFM patterning and gate cut processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional WFM patterning is used in nanosheet devices, then manufacturing simplicity is maintained, but manufacturing precision deteriorates due to overetching and damage to the WFM
Solution Approach 1:
A mandrel structure is introduced as an intermediary element between the WFM and the etching process. The mandrel serves as a protective template that defines the gate cut region and prevents direct etching damage to the WFM, thereby improving patterning precision while managing process complexity through a controlled intermediate step
Solution Approach 2:
The gate cut is formed preliminarily using the mandrel as a mask before the WFM is fully patterned. This preliminary action establishes the gate region boundaries in advance, preventing overetching during subsequent WFM patterning steps and ensuring precise alignment
2Productivity
If feature sizes are reduced to increase device density, then productivity is improved, but manufacturing precision deteriorates due to increased susceptibility to overetching
Solution Approach 1:
The mandrel acts as a protective intermediary that becomes increasingly important at smaller feature sizes. It provides a physical barrier that prevents etching tools from damaging the WFM, ensuring consistent patterning precision even as device dimensions are reduced to increase density
Solution Approach 2:
The mandrel structure provides beforehand cushioning by absorbing the harshness of the etching process. It is designed to be removed after serving its protective function, having already cushioned the WFM against overetching damage during the critical patterning step
Data Source
AI summary
A semiconductor device fabrication method is provided and includes building first and second nanosheet devices, locating a dielectric bar between the first and second nanosheet devices, forming, in the first nanosheet device, a first work function metal (WFM) and forming in the second nanosheet device, a second WFM that extends across the dielectric bar and the first WFM.