Self-Aligned Contact Rail Using a Sacrificial Fin Template
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Solution Overview
Problem
Conventional semiconductor devices, such as vertical transport field effect transistors (VTFETs), face issues with non-self-aligned contact rails leading to parasitic shorts due to large critical dimensions, which necessitate the development of a self-aligned contact rail with reduced critical dimensions.
Innovation Solution
The use of a sacrificial semiconductor fin as a placeholder structure allows for the formation of a self-aligned contact rail with a lower portion having a critical dimension of 25 nm or less, achieved through a method involving the formation of sacrificial and active fins, dielectric material stacks, and selective etching to create a contact rail opening that exposes the source/drain region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional non-self-aligned contact rail formation is used, then the manufacturing process is simpler, but the critical dimension is large (25 nm or greater) leading to parasitic shorts
Solution Approach 1:
A sacrificial semiconductor fin is formed in advance at the desired contact rail location. This preliminary structure serves as a template that defines the exact position and dimensions of the future contact rail, enabling self-alignment without requiring precise overlay during subsequent processing steps.
Solution Approach 2:
The sacrificial semiconductor fin acts as an intermediary structure that temporarily occupies the contact rail position. It mediates between the source/drain region and the final contact rail, allowing the contact rail to be formed with precise alignment by transferring the pattern from the sacrificial fin through dielectric deposition and etching processes.
2Manufacturing precision
If conventional lithographic processes are used, then the manufacturing process is simpler, but the critical dimension is greater than 25 nm
Solution Approach 1:
The sacrificial semiconductor fin is formed with the desired small critical dimension (25 nm or less) before the contact rail formation process. This preliminary structuring allows the final contact rail to inherit the precise dimensions of the sacrificial fin, achieving small CD without requiring advanced lithography for the contact rail itself.
Solution Approach 2:
The contact rail pattern is copied from the sacrificial semiconductor fin through conformal dielectric deposition and anisotropic etching. The sacrificial fin serves as a master template, and the contact rail is created as a precise replica, transferring the small critical dimension from the sacrificial structure to the functional contact rail.
3Reliability
If self-aligned contact rail formation is implemented, then parasitic shorts are eliminated, but the manufacturing process becomes more complex
Solution Approach 1:
The sacrificial semiconductor fin serves as an intermediary that enables self-alignment. By forming the contact rail through the sacrificial fin template rather than direct lithographic patterning, the method achieves perfect alignment with the source/drain region, eliminating parasitic shorts while using standard processing techniques.
Solution Approach 2:
The sacrificial semiconductor fin is self-aligned with the source/drain region by default since it is formed in the same location. This self-alignment property eliminates the need for complex overlay procedures, as the sacrificial fin automatically provides the correct position and dimensions for the contact rail without requiring additional alignment steps.
Data Source
AI summary
A semiconductor device containing a self-aligned contact rail is provided. The self-aligned contact rail can have a reduced critical dimension, CD. The self-aligned contact rail can be obtained utilizing a sacrificial semiconductor fin as a placeholder structure for the contact rail. The used of the sacrificial semiconductor fin enables reduced, and more controllable, CDs.