Wrap-Around Contact Layout With Early Contact Cut Margin
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving optimal contact resistance reduction for advanced technologies beyond the 10 nm node, particularly in forming wrap-around contacts for finFETs and other 3D structures, where the existing processes have a narrow process margin and difficulty in achieving effective contact with both top and sidewall surfaces of source/drain epitaxial regions.
Innovation Solution
The method involves forming p-type and n-type epitaxial regions over a substrate, creating a dielectric pillar between them, depositing sacrificial liners, and forming trenches in an inter-layer dielectric to expose these regions, followed by filling the openings with a conductive material to create a wrap-around contact that contacts both the top and sidewalls of the epitaxial regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wrap around contact is formed to contact both top and sidewall surfaces of S/D epi, then contact area is increased and contact resistance is reduced, but process margin becomes very small
Solution Approach 1:
The contact cut is performed early in the process sequence, before subsequent deposition steps that would add material over the contact region. This preliminary timing ensures that the contact opening dimensions are established before any material buildup that could encroach on the contact area, thereby maintaining adequate process margin while still achieving the wrap-around contact geometry that contacts both top and sidewall surfaces
Solution Approach 2:
The wrap around contact structure is formed by segmenting the contact formation process into distinct stages: first creating the contact cut early, then depositing sacrificial liners and inter-layer dielectric, and finally forming the conductive material. This segmentation allows precise control of each step independently, maintaining process margin while achieving the complex geometry needed to contact both top and sidewall surfaces
2Manufacturing precision
If trenches are formed to extend into sacrificial liners, then openings are defined to expose epitaxial regions, but alignment precision requirements increase
Solution Approach 1:
Sacrificial liners are deposited as intermediary layers between the trench formation and the final contact structure. These liners extend into the trenches and serve as temporary placeholders that define the opening geometry. The liners are later removed to create the final openings, but their presence during trench formation provides a robust alignment reference that reduces precision requirements compared to direct contact hole formation
Solution Approach 2:
The sacrificial liners are deposited preliminarily before trench formation, creating a pre-defined template for the opening locations. This preliminary placement of liners establishes the alignment framework early, allowing subsequent trench etching to follow the liner boundaries rather than requiring direct alignment to underlying features, thereby reducing alignment precision requirements
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 increases the contact area and reduces contact resistance by ensuring effective contact with both surfaces of the source/drain epitaxial regions, enhancing the performance of semiconductor devices beyond the 10 nm technology node.
Implementation Method 1
filling the irregular-shaped openings with a conductive material defining the wrap around contact
Data Source
AI summary
A method is presented for forming a wrap around contact. The method includes forming a p-type epitaxial region and an n-type epitaxial region over a substrate, forming a dielectric pillar between the p-type epitaxial region and the n-type epitaxial region, depositing sacrificial liners around both the p-type epitaxial region and the n-type epitaxial region, and depositing an inter-layer dielectric (ILD). The method further includes forming trenches in the ILD extending into the sacrificial liners, wherein the trenches are vertically aligned with the p-type epitaxial region and the n-type epitaxial region, removing the sacrificial liners to define irregular-shaped openings exposing the p-type epitaxial region and the n-type epitaxial region, and filling the irregular-shaped openings with a conductive material defining the wrap around contact.