Immersion Lithography Multiple Exposure Sub-40nm Patterning
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in achieving fine patterns due to limitations in numerical aperture of lenses, which restricts the resolution of photoresist patterns, especially when using conventional light sources, and the high costs associated with extreme ultraviolet light sources for improved resolution.
Innovation Solution
A method involving multiple exposure processes using immersion lithography with different photomasks to form variously shaped photoresist patterns, which are then used as masks to etch the target layer, allowing for the creation of sub-40 nm patterns with improved accuracy and reduced manufacturing complexity compared to double patterning technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional light sources with limited numerical aperture are used, then manufacturing costs are lower, but pattern resolution cannot achieve sub-40 nm features
Solution Approach 1:
The patent divides the patterning process into multiple exposure steps, where a first exposure forms initial patterns and a second exposure forms additional patterns in the gaps between first patterns. This segmentation allows achieving sub-40 nm resolution using conventional light sources without requiring expensive EUV equipment, as each exposure step operates within the capabilities of standard lithography systems.
Solution Approach 2:
The patent introduces a temporal dimension by performing multiple exposure processes sequentially rather than attempting to form all patterns in a single exposure. This multi-step approach in the time domain enables resolution beyond the single-exposure limit of conventional light sources, avoiding the need for costly alternative light sources.
2Manufacturing precision
If single exposure process is used, then manufacturing process is simpler, but pattern density and resolution are insufficient for advanced nodes
Solution Approach 1:
The exposure process is segmented into at least two distinct exposure steps: a first exposure that creates sparsely distributed patterns, and a second exposure that fills the gaps between first patterns. This segmentation increases overall pattern density while keeping each individual exposure step relatively simple, balancing complexity and performance.
Solution Approach 2:
The first exposure process intentionally creates a sparse pattern with larger spacing than the final desired pattern density. This partial action leaves room for the second exposure to add additional patterns, achieving higher overall density without requiring either exposure step to be overly complex.
3Manufacturing precision
If photoresist patterns are formed too close together, then pattern density increases, but pattern collapse occurs during development
Solution Approach 1:
The patent segments the pattern formation into two stages: first, sparse patterns are formed with sufficient spacing to maintain structural stability during development; second, additional patterns are formed in the gaps between first patterns. This segmentation ensures that no single photoresist pattern is subjected to excessive stress from neighboring patterns, preventing collapse while achieving high overall density.
Solution Approach 2:
The first exposure process performs a preliminary action of creating a stable, sparsely distributed pattern framework first. This preliminary structure provides mechanical support and stability, and only after this stable framework is established does the second exposure add additional patterns, ensuring that patterns are formed in a stable configuration rather than attempting to create dense patterns directly.
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 method enhances pattern resolution and accuracy while reducing manufacturing complexity and costs by utilizing immersion lithography and multiple exposure processes to form precise photoresist patterns that serve as effective masks for etching, enabling the creation of fine features without the need for high-cost extreme ultraviolet light sources.
Implementation Method 1
performing a first exposure process to transform first portions of the photoresist layer into first photoresist patterns spaced apart from each other and performing a second exposure process to transform second portions of the photoresist layer into second photoresist patterns spaced apart from each other
Implementation Method 2
The numerical aperture NA is proportional to n.sin θ, where n is a refractive index of a medium interposed between the lens and the photoresist. The minimum distance between resolvable points may decrease using the medium having a higher the refractive index. Immersion lithography processes use a medium having a refractive index that is higher than a refractive index of the air
Data Source
AI summary
Methods of forming patterns are provided. The methods may include sequentially forming an etch-target layer and a photoresist layer on a substrate, exposing two first portions of the photoresist layer to light to transform the two first portions into two first photoresist patterns and exposing a second portion of the photoresist layer to light to transform the second portion into a second photoresist pattern disposed between the two first photoresist patterns. The method may also removing portions of the photoresist layer to leave the two first photoresist patterns and the second photo resist pattern on the etch-target layer such that the etch-target layer is exposed.