FinFET Replacement Gate Process for Fin Buckling
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Solution Overview
Problem
In semiconductor integrated circuit fabrication, particularly in FinFET processes, free-standing fins with high aspect ratios often buckle or collapse during cleaning and drying processes due to lack of support, leading to manufacturing challenges.
Innovation Solution
The method involves forming fins over a substrate, filling trenches with an isolation layer, and supporting the fins with a dielectric layer and dummy gate structures to prevent buckling and collapsing during subsequent cleaning processes, ensuring the fins are protected throughout the fabrication stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fins with high aspect ratio are formed to improve gate control and reduce short-channel effects, then device performance is improved, but the fins become prone to buckling and collapsing during cleaning and drying processes
Solution Approach 1:
A mandrel structure is formed prior to the fins to provide support during subsequent processing steps. The mandrel is positioned at the base of the fins before cleaning and drying operations, preventing buckling and collapsing during these critical processes. The mandrel is later removed after serving its protective function.
Solution Approach 2:
The mandrel acts as an intermediary support structure between the substrate and the high aspect ratio fins. It provides mechanical support during cleaning and drying processes, enabling the fins to maintain their structural integrity without requiring permanent structural modifications to the fin design.
2Device complexity
If a replacement gate process is used to improve device performance, then the number of high temperature processing steps is reduced, but the fins remain vulnerable to damage during intermediate processing steps
Solution Approach 1:
The mandrel structure is established before the replacement gate process begins, providing continuous support through all intermediate steps including cleaning, drying, and gate formation. This preliminary support structure enables the simplified replacement gate process to proceed without compromising fin integrity.
Solution Approach 2:
The mandrel material is selected to have different etch selectivity compared to the fin material, allowing the mandrel to be removed after serving its protective function. This parameter difference enables the mandrel to be selectively removed without damaging the fins or other device structures.
Data Source
AI summary
A method of forming a semiconductor device includes etching a substrate to form two first trenches separated by a fin; filling the two first trenches with an isolation layer; and depositing a dielectric layer over the fin and the isolation layer. The method further includes forming a second trench in the dielectric layer over a channel region of the semiconductor device, the second trench exposing the isolation layer. The method further includes etching the isolation layer through the second trench to expose an upper portion of the fin in the channel region of the semiconductor device, and forming a dummy gate in the second trench over the isolation layer and engaging the upper portion of the fin.