Direct Metal Etch Interconnect Patterning for Lower LWR and LER
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Solution Overview
Problem
As semiconductor devices shrink, they face challenges such as line width roughness (LWR), line edge roughness (LER), and line wiggle due to etching into low-k films with poor mechanical hardness, leading to issues like shorts and cross-talk in metal lines.
Innovation Solution
A self-aligned direct metal etch approach is used to form and fill metal gaps, resulting in a metal film with higher mechanical hardness, which reduces LWR and LER, and allows for larger critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional damascene processes are used to form metal trenches and vias, then metal interconnect structures can be formed, but line width roughness (LWR) and line edge roughness (LER) increase due to etching into low-k films with poor mechanical hardness
Solution Approach 1:
The patent introduces a mandrel structure as an intermediary element during the etching process. The mandrel provides mechanical support and defines the precise pattern geometry, allowing the etch to proceed without directly compromising the mechanical hardness of the low-k film. This intermediary structure enables high manufacturing precision while preserving the integrity of the underlying low-k material.
Solution Approach 2:
The self-aligned direct metal etch process uses the deposited metal film itself to define the pattern boundaries through controlled etching. The metal film serves its dual function as both the conductive interconnect and the pattern-defining element, eliminating the need for separate mandrel structures and reducing the mechanical stress on the low-k film while maintaining manufacturing precision.
2Productivity
If critical dimension and pitch are scaled down to accommodate smaller semiconductor devices, then device density increases, but line wiggle and shorts between metal lines increase due to etching into mechanically soft low-k films
Solution Approach 1:
The patent performs preliminary deposition of a metal film before the etching process. This pre-deposited metal film serves as a rigid structural framework that prevents line wiggle during subsequent etching operations. By establishing this stable structure in advance, the process enables smaller critical dimensions and higher device density while maintaining reliability by preventing shorts and cross-talk between adjacent metal lines.
3Manufacturing precision
If direct metal etch is used to form metal patterns, then mechanical hardness of metal film increases and LWR/LER decreases, but additional process steps are required
Solution Approach 1:
The patent merges the pattern definition function and the conductive interconnect function into a single integrated process step. The direct metal etch process simultaneously creates the precise pattern geometry and forms the functional metal interconnect structure, eliminating the need for separate mandrel deposition, patterning, and removal steps. This consolidation reduces overall process complexity while achieving superior manufacturing precision with reduced LWR and LER.
Data Source
AI summary
In one embodiment, a method of forming metal interconnects uses a direct metal etch approach to form and fill the metal gap. The method may include directly etching a metal layer to form metal patterns. The metal patterns may be spaced apart from one another by recesses. A dielectric spacer may be formed extending along the sidewalls of each of the recesses. The recesses may be filled with a conductive material to form a second set of metal patterns. By directly etching the metal film, the technique allows for reduced line width roughness. The disclosed structure may have the advantages of increased reliability, better RC performance and reduced parasitic capacitance.