EUV Lithography Edge Smoothing via Passivation Layer
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Solution Overview
Problem
Current EUV lithography methods result in poor edge roughness and weak patterns, rendering substrates useless due to high local critical dimension uniformity (LCDU) and stochastic effects from higher energy photons.
Innovation Solution
A multi-cycle deposition-etch operation is performed, where a passivation layer preferentially collects in crevices, and protuberances are etched away, reducing roughness, and a thin layer is deposited in holes with varying critical dimensions, preferentially removing it from the bottoms to achieve smoother features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EUV lithography is used to pattern small critical dimension features, then lithographic resolution is improved, but edge roughness and local critical dimension uniformity deteriorate
Solution Approach 1:
A passivation layer is deposited before the main etch process to preemptively protect crevices from etching. This preliminary action ensures that recessed areas are shielded from the etchant, preventing the formation of rough edges and maintaining smooth feature profiles while enabling high-resolution patterning
Solution Approach 2:
The passivation layer acts as an intermediary material between the etchant and the feature crevices. It selectively protects recessed areas during etching, mediating the interaction between the aggressive etchant and the vulnerable feature geometry to achieve smooth edges without compromising pattern fidelity
2Measurement precision
If EUV lithography is used to pattern small critical dimension features, then lithographic resolution is improved, but local critical dimension uniformity deteriorates
Solution Approach 1:
The passivation layer is deposited in advance to preemptively protect crevices, ensuring uniform etching rates across features with varying geometries. This preliminary protection mechanism maintains consistent critical dimensions across different feature sizes and shapes, improving local CD uniformity
Solution Approach 2:
The passivation layer provides localized protection specifically at crevices and recessed areas where etching would otherwise cause non-uniformity. By applying protection only where needed rather than uniformly across all surfaces, the process maintains precise local critical dimension control while enabling high-resolution patterning
3Manufacturing precision
If a passivation layer is deposited to protect crevices, then edge roughness is improved, but process complexity increases
Solution Approach 1:
The passivation layer deposition and subsequent etch process are merged into an integrated sequence where the passivation step is immediately followed by the etch step. This combination allows the complexity of the multi-step process to be managed as a unified workflow, achieving smooth edges without excessive procedural overhead
4Manufacturing precision
If multiple deposition-etch cycles are performed, then local critical dimension uniformity is improved, but manufacturing time increases
Solution Approach 1:
The deposition-etch sequence is performed in periodic cycles, with each cycle consisting of a deposition step followed by an etch step. This periodic repetition allows progressive improvement of local CD uniformity through multiple iterations, with each cycle refining the feature geometry further while managing overall process time through efficient cycling
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 significantly reduces LCDU, achieving line edge roughness and critical dimension uniformity below 1 nm, improving the quality of patterned features and extending lithographic capabilities beyond conventional limits.
Implementation Method 1
depositing passivation layer that preferentially collects in crevices of a feature leaving protuberances exposed
Implementation Method 2
etching the feature to remove the exposed protuberances
Implementation Method 3
performing a multi-cycle deposition-etch operation... significantly reduces LCDU, achieving line edge roughness and critical dimension uniformity below 1 nm
Data Source
AI summary
Provided herein are methods and related apparatus to smooth the edges of features patterned using extreme ultraviolet (EUV) lithography. In some embodiments, at least one cycle of depositing passivation layer that preferentially collects in crevices of a feature leaving protuberances exposed, and etching the feature to remove the exposed protuberances, thereby smoothing the feature, is performed. The passivation material may preferentially collect in the crevices due to a higher surface to volume ratio in the crevices than in the protuberances. In some embodiments, local critical dimension uniformity (LCDU), a measure of roughness in contact holes, is reduced. In some embodiments, at least one cycle of depositing a thin layer in a plurality of holes formed in photoresist, the holes having different CDs, wherein the thin layer preferentially deposits in the larger CD holes, and anisotropically removing the thin layer to remove it at the bottoms of the holes, is performed.