Spacer-Assisted Metal Cut Patterning for BEOL Interconnects
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Solution Overview
Problem
Conventional semiconductor fabrication techniques for back-end-of-line (BEOL) metal cuts face challenges such as complexity, scalability issues, misaligned breaks in metallic lines, edge roughness, and increased line resistances and parasitic capacitance.
Innovation Solution
The proposed method involves a Spacer-Assisted Litho-Etch Spacer-Assisted Litho-Etch (SALESALE) double patterning technique, which includes forming mandrel layers with spacer materials to create self-aligned metal cuts, eliminating the need for pillaring and addressing misalignment and edge roughness through precise spacer placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional patterning methodologies are used to form metallic lines, then the process can be implemented with existing tools, but the methodology is complex, fails to address scalability concerns, and produces misaligned breaks in metallic lines
Solution Approach 1:
The spacer structures self-align to the mandrel patterns through conformal deposition, automatically defining the position of metallic line breaks without requiring additional alignment steps or complex patterning processes. The spacer material inherently serves the dual function of defining both the metallic line position and the break location.
Solution Approach 2:
The patterning process is segmented into distinct stages: forming mandrels, depositing spacers, selectively removing mandrels, and forming metallic lines. This segmentation allows each stage to be optimized independently and simplifies the overall process by breaking down the complex alignment problem into manageable steps.
2Manufacturing precision
If conventional etching processes are used, then the process can be completed in fewer steps, but edge roughness increases and line resistances and parasitic capacitance increase
Solution Approach 1:
The spacer material acts as an intermediary between the mandrel pattern and the final metallic line structure. It provides a controlled interface that enables precise definition of line edges and break locations, reducing edge roughness while maintaining manufacturing efficiency through the self-aligned nature of the process.
3Measurement precision
If spacer materials are used to define metal cuts, then alignment accuracy and scalability are improved, but additional materials and process steps are required
Solution Approach 1:
The spacer structures serve multiple functions simultaneously: they define the position of metallic lines, define the location of line breaks, and provide self-alignment references for subsequent processing steps. This multi-functionality reduces the need for additional dedicated structures or alignment marks.
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 the accuracy and scalability of metal cuts, reducing parasitic capacitance and line resistances, and improves the yield and functionality of metallic interconnect structures by enabling precise alignment and reduced edge roughness.
Implementation Method 1
depositing a first spacer material within the first recessed profile wherein the spacer material within the first wing segment defines a first spacer
Implementation Method 2
performing at least one etching process selective to the first and second spacer materials to remove exposed portions of the first and second mandrel layers
Data Source
AI summary
A method includes forming a dielectric layer on a semiconductor substrate, forming a first mandrel layer and a second mandrel layer on the dielectric layer and patterning the first mandrel layer and the second mandrel layer to form respective first and second patterns in the first and second mandrel layers. The first pattern includes a first line segment and a first wing segment. The first wing segment is filled with a first spacer material to form a first spacer. The method further includes removing exposed portions of the first and second mandrel layers, transferring an image of the first and second patterns, patterning the dielectric layer and depositing a metal into the patterned dielectric layer to form a metallic interconnect structure. The metallic interconnect structure includes first and second metallic lines with the second metallic line having a line break corresponding to the first spacer.