Cut EPI Source/Drain Structure to Prevent FinFET Merging Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor devices scale down, epitaxially growing source/drain (S/D) features becomes increasingly challenging due to the risk of EPI merging defects, where large EPIs merge or contact each other accidentally, leading to short circuit defects and reduced device integration.
Innovation Solution
The proposed solution involves a cut EPI process that is applied to S/D EPI features after epitaxial growth but before depositing a contact etch stop layer. This process selectively removes portions of the S/D features to separate merged features and increase spacing between them, thereby preventing merging defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large epitaxial source/drain features are grown to reduce contact resistance, then contact resistance decreases, but spacing requirements increase and device integration is reduced
Solution Approach 1:
The patent applies segmentation by dividing the epitaxial growth process into two distinct stages: a first epitaxial growth stage that forms initial source/drain features, and a second epitaxial growth stage that forms additional source/drain features. This segmentation allows each stage to be optimized independently, enabling sufficient feature size for low contact resistance while maintaining adequate spacing for high device integration through selective growth control in different temporal and spatial contexts.
2Productivity
If spacing among source/drain features is reduced to increase device integration, then device integration increases, but source/drain features may merge and cause short circuit defects
Solution Approach 1:
The patent applies preliminary action by performing the first epitaxial growth stage before the second epitaxial growth stage, where the first stage establishes initial source/drain features with controlled dimensions. This preliminary formation creates a foundation that prevents subsequent merging during the second growth stage, as the features are already sized and positioned to accommodate further growth without merging, thereby enabling reduced spacing while maintaining reliability.
Solution Approach 2:
The patent applies dynamics by implementing a multi-stage epitaxial growth process where growth conditions, duration, and parameters are dynamically adjusted between stages. The first stage uses specific growth parameters to form initial features, while the second stage uses different parameters to add material without causing merging. This dynamic control of growth conditions allows precise management of feature dimensions and spacing, enabling high device integration without short circuit defects.
3Reliability
If multi-stage epitaxial growth is implemented to resolve merging issues, then merging defects are prevented, but process complexity increases
Solution Approach 1:
The patent applies merging by combining multiple epitaxial growth stages into a unified process flow that uses the same fundamental epitaxial growth technology throughout. Rather than introducing entirely different process techniques, the solution merges multiple growth operations with adjusted parameters into a single coherent process sequence, preventing merging defects through controlled staged growth while minimizing the increase in process complexity by leveraging existing process capabilities.
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
The cut EPI process improves the yield window, particularly for advanced process nodes, by preventing EPI merging defects, allowing for more densely packed fins, and enhancing S/D EPI quality and process robustness.
Implementation Method 1
epitaxially growing two source/drain features in the two source/drain trenches respectively
Implementation Method 2
performing a cut process to the two source/drain features
Data Source
AI summary
A device includes a substrate, an isolation structure over the substrate, and two fins extending from the substrate and above the isolation structure. Two source/drain structures are over the two fins respectively and being side by side along a first direction generally perpendicular to a lengthwise direction of the two fins from a top view. Each of the two source/drain structures has a near-vertical side, the two near-vertical sides facing each other along the first direction. A contact etch stop layer (CESL) is disposed on at least a lower portion of the near-vertical side of each of the two source/drain structures. And two contacts are disposed over the two source/drain structures, respectively, and over the CESL.