Mandrel And Spacer Patterning Beyond EUV Resolution Limits
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Solution Overview
Problem
Conventional extreme ultraviolet (EUV) lithography scanners face limitations in printing structures with critical dimensions below 20 nm, as they reach their resolution limit, making it challenging to manufacture features with sizes smaller than the targeted critical dimension.
Innovation Solution
A method involving a substrate with a structure comprising a distal portion, a proximal portion, and parallel sidewalls, where etching cycles with conversion and volatilization pulses are used to thin the structure, forming a mandrel with a critical dimension smaller than the optical resolution limit, utilizing different compositions for the layers and employing specific reactants like oxygen and fluorine species.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional EUV lithography is used to pattern structures, then the manufacturing process is simple and well-established, but the critical dimension resolution is limited to approximately 20 nm or larger
Solution Approach 1:
The patterning process is segmented into multiple distinct stages: initial structure formation, mandrel formation through cyclical etching, spacer deposition, and final pattern transfer. This segmentation allows each stage to be optimized independently, achieving sub-20 nm resolution through the combination of steps rather than relying on a single lithographic exposure
Solution Approach 2:
Mandrels are formed in advance before the final pattern is transferred to the target layer. These preliminary mandrel structures serve as templates that define the subsequent feature locations and dimensions, enabling precise control of critical dimensions below the direct lithographic resolution limit
2Manufacturing precision
If the structure is thinned to form mandrels with small critical dimensions, then features below 20 nm can be patterned, but lateral edge roughness may increase
Solution Approach 1:
The etching process uses periodic cyclical pulses alternating between etching reactants and purge/reactant phases. This periodic action allows controlled, incremental removal of material from the structure sidewalls, forming smooth mandrel edges with precise dimensional control while minimizing lateral edge roughness through gradual thinning
Solution Approach 2:
Different reactant parameters are used at different stages: oxygen-based reactants for conversion/oxidation phases and fluorine-based reactants for etching phases. By changing reactant composition and processing conditions, the etch rate and surface morphology are controlled to achieve smooth edges on thinned mandrels
3Manufacturing precision
If multiple etching cycles with conversion and volatilization pulses are used to form mandrels, then resolution below optical limit is achieved, but process time and complexity increase
Solution Approach 1:
The cyclical etching process continuously alternates between material conversion and selective removal phases without interrupting the mandrel formation objective. Each cycle builds upon the previous one, progressively refining the mandrel dimensions toward the target sub-20 nm critical dimension through uninterrupted iterative processing
Solution Approach 2:
A spacer layer is introduced as an intermediary material between the mandrel and the final patterned features. This spacer enables the transfer of the mandrel's precisely controlled dimensions to the target layer through conformal deposition and subsequent anisotropic etching, achieving high precision without requiring excessively complex direct etching sequences
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 allows for the formation of mandrels with small critical dimensions and low lateral edge roughness, enabling the patterning of features with dimensions less than 20 nm, thereby overcoming the resolution limits of conventional EUV lithography.
Implementation Method 1
The conversion pulse comprises exposing the substrate to a conversion reactant. Thus, a converted surface layer is formed on the sidewalls. In some embodiments, the conversion reactant comprises an oxygen reactant.
Implementation Method 2
The volatilization pulse comprises exposing the substrate to a volatilization reactant. Thus, the converted surface layer is volatilized. In some embodiments, the volatilization reactant comprises a fluorine species.
Data Source
AI summary
Methods for patterning and forming structures, as well as related structures and systems are disclosed. The methods comprise forming a mandrel on a substrate. Forming the mandrel comprises executing a plurality of etching cycles to thin a structure.