Silicon Nitride Diffusion Break for RMG Isolation
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Solution Overview
Problem
Conventional lithography and etch techniques struggle to pattern isolation trenches in semiconductor devices with small critical dimensions, leading to leakage issues and asymmetric epitaxial growth, which complicates source and drain contact placement and creates potential leakage paths.
Innovation Solution
Forming a diffusion break by depositing silicon nitride within an opening that extends through the dielectric material, epitaxial junction area, and into the substrate between replacement metal gate structures and fins, thereby creating a semiconductor device with improved isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography and etch techniques are used to pattern isolation trenches, then the process is simple and widely available, but the critical dimensions cannot be achieved with sufficient precision and leakage paths remain
Solution Approach 1:
The patent forms the isolation trench structure before the final metal gate deposition step. By preparing the trench structure early in the process flow and then using subsequent deposition and etch steps to define the precise pattern, the method achieves high precision without requiring advanced lithography on the final gate structure.
Solution Approach 2:
The patent introduces an intermediate structure (the isolation trench filled with dielectric material and containing the diffusion break) that mediates between the substrate and the final metal gate structure. This intermediate structure enables precise critical dimension control by serving as a template or guide for subsequent processing steps.
2Reliability
If a dummy gate is used to enable diffusion break, then isolation is achieved, but leakage occurs through the dummy gate and asymmetric epitaxial growth results
Solution Approach 1:
The patent removes the problematic dummy gate structure entirely and replaces it with a diffusion break formed directly in the substrate. By extracting the dummy gate element that causes leakage and asymmetric growth, the invention achieves isolation through a cleaner, more effective diffusion barrier that does not generate harmful leakage paths.
Solution Approach 2:
The patent changes the fundamental parameter of how isolation is achieved - transitioning from using a dummy gate structure (geometric approach) to using a diffusion break (material property approach). By changing from structural isolation to diffusion-based isolation, the method eliminates leakage while achieving symmetric epitaxial growth.
3Ease of manufacture
If isolation trench is made larger than dummy gate, then fabrication is easier, but epitaxial growth becomes non-ideal and contact placement is compromised
Solution Approach 1:
The patent performs preliminary formation of the isolation trench structure with precise dimensions before epitaxial growth. By establishing the correct trench geometry early and using it as a template, the subsequent epitaxial growth naturally follows the predefined boundaries, achieving ideal facets without requiring larger or less precise trenches.
Solution Approach 2:
The patent designs the isolation trench structure to serve multiple functions: it defines the isolation boundary, guides the epitaxial growth facets, and positions the diffusion break. This self-service structure eliminates the need for separate dummy gate structures and achieves precise epitaxial geometry through the trench design itself.
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
This approach enhances device isolation, reduces leakage, and ensures ideal facet growth for epitaxial source and drain structures, facilitating better contact placement and reducing current crowding issues.
Implementation Method 1
silicon nitride (SiN) deposited within the opening to form a diffusion break
Data Source
AI summary
Embodiments herein provide approaches for forming a diffusion break during a replacement metal gate process. Specifically, a semiconductor device is provided with a set of replacement metal gate (RMG) structures over a set of fins patterned from a substrate; a dielectric material over an epitaxial junction area; an opening formed between the set of RMG structures and through the set of fins, wherein the opening extends through the dielectric material, the expitaxial junction area, and into the substrate; and silicon nitride (SiN) deposited within the opening to form the diffusion break.