Positive Resist Composition for EUV Lithography
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Solution Overview
Problem
In the context of microelectronic device manufacturing, existing resist compositions face challenges in achieving high sensitivity, resolution, and reduced edge roughness while maintaining dimensional uniformity as feature sizes decrease, primarily due to acid diffusion issues during the lithography process.
Innovation Solution
A positive resist composition is developed using a base polymer with repeat units containing sulfonium or iodonium salt structures of trihydrocarbylsulfonylmethide acid, which minimizes acid diffusion and enhances dissolution contrast, incorporating acid labile groups to improve sensitivity and resolution, and features a low swelling characteristic in alkaline developers for uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid diffusion is reduced to improve resolution, then edge roughness decreases, but sensitivity declines
Solution Approach 1:
The patent changes the chemical parameters of the acid generator by using sulfonium or iodonium salts with specific structural features (bulky acid generation) to modify acid diffusion characteristics. This allows resolution improvement without complete sensitivity loss by tuning the acid generation properties rather than simply reducing diffusion distance
Solution Approach 2:
The resist composition uses a composite approach by combining polymer-bound acid generators with specific base polymers and additives. This composite material system balances acid diffusion control with sufficient acid generation to maintain sensitivity, resolving the contradiction between resolution and sensitivity
2Manufacturing precision
If post exposure bake temperature and time are reduced to minimize acid diffusion, then resolution improves, but sensitivity and contrast drastically reduce
Solution Approach 1:
The patent changes the chemical parameters of the acid generation system by incorporating sulfonium or iodonium salts that generate bulky acids with controlled diffusion. This allows the use of reduced PEB temperature and time while maintaining both sensitivity/contrast and resolution, as the acid generation efficiency compensates for the reduced thermal processing
3Productivity
If feature size is reduced to increase integration density, then manufacturing capability improves, but acid diffusion control becomes more difficult
Solution Approach 1:
The patent applies local quality by using polymer-bound acid generators where the acid generation occurs at specific locations within the polymer structure. This localized acid generation improves control over acid diffusion even at reduced feature sizes, enabling higher integration density while maintaining pattern fidelity
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
The resist composition achieves high sensitivity, resolution, and reduced edge roughness with improved dimensional uniformity, making it suitable for advanced micropatterning applications such as VLSIs and photomasks, particularly effective with EUV lithography.
Implementation Method 1
a base polymer containing repeat units (a) having a sulfonium salt structure or an iodonium salt structure of trihydrocarbylsulfonylmethide acid free of a fluorine atom on a carbon atom at an α-position of a sulfonyl group
Data Source
AI summary
There is provided a positive resist composition that exhibits higher sensitivity and resolution than those of conventional positive resist compositions, has reduced edge roughness (LWR), has satisfactory dimensional uniformity (CDU), and has a satisfactory pattern profile after exposure, and to provide a pattern forming process. The positive resist composition comprises a base polymer containing repeat units (a) having a sulfonium salt structure or an iodonium salt structure of trihydrocarbylsulfonylmethide acid free of a fluorine atom on a carbon atom bonded to a sulfonyl group.