Backside Contact Alignment in Nanoribbon Transistor Fabrication
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Solution Overview
Problem
State-of-the-art approaches to forming backside contacts for transistors, particularly non-planar transistors like nanoribbon-based devices, face limitations in alignment and integration due to their complex architectures.
Innovation Solution
A method involving the use of a placeholder for backside contact formation, where a dielectric placeholder is used to align contacts with device ports in nanoribbon-based transistors, allowing for precise placement and integration of backside contacts during the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional approaches are used to form backside contacts for non-planar transistors, then the manufacturing process can be completed, but alignment precision and integration quality deteriorate due to complex transistor architectures
Solution Approach 1:
A placeholder structure is introduced as an intermediary element during the backside contact formation process. This placeholder serves as a temporary reference structure that enables precise alignment of contact holes with the underlying transistor ports. After the contact holes are formed and aligned using the placeholder, the placeholder is removed. This intermediary approach resolves the alignment precision issue without requiring direct visualization or manipulation of the complex transistor architecture itself.
Solution Approach 2:
The placeholder structure is formed in advance before the backside contact holes are etched. This preliminary action establishes a reference framework that guides subsequent alignment operations. By preparing the alignment reference beforehand, the process accommodates the complex transistor architecture without compromising the precision of contact formation.
2Productivity
If direct backside contact formation is attempted without placeholders, then the process steps are reduced, but alignment and integration quality worsen due to inability to precisely locate device ports
Solution Approach 1:
The placeholder acts as a temporary intermediary that enables precise alignment without adding significant process complexity. It provides a visible reference structure that can be easily aligned with using standard lithography techniques, thereby maintaining manufacturing efficiency while dramatically improving contact alignment precision.
Solution Approach 2:
The placeholder is a temporary, disposable structure that is formed, used for alignment, and then removed. It serves its purpose during the critical alignment phase and is subsequently eliminated, leaving no trace in the final device. This approach allows for high precision without permanently adding complex structures to the device.
3Manufacturing precision
If placeholders are used for backside contact formation, then alignment precision improves, but the number of process steps increases
Solution Approach 1:
The formation of the placeholder is merged with existing process steps where possible. For example, the placeholder may be formed using the same lithography and deposition processes that are already part of the manufacturing flow, thereby minimizing the addition of discrete process steps while still achieving the alignment precision benefit.
Data Source
AI summary
Methods for fabricating a transistor arrangement of an IC structure by using a placeholder for backside contact formation, as well as related semiconductor devices, are disclosed. An example method includes forming, in a support structure (e.g., a substrate, a chip, or a wafer), a dielectric placeholder for a backside contact as the first step in the method. A nanosheet superlattice is then grown laterally over the dielectric placeholder, and a stack of nanoribbons is formed based on the superlattice. The nanoribbons are processed to form S/D regions and gate stacks for future transistors. The dielectric placeholder remains in place until the support structure is transferred to a carrier wafer, at which point the dielectric placeholder is replaced with the backside contact. Use of a placeholder for backside contact formation allows alignment of contact from the backside to appropriate device ports of a transistor arrangement.