Lithography Resist Swelling Reduction via Cross-Linking
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Solution Overview
Problem
Current lithography techniques face challenges in achieving sufficient resist contrast and minimizing line edge roughness (LER) and line width roughness (LWR) due to resist swelling issues during the development process, particularly at advanced technology nodes below 14 nanometers, where positive tone development (PTD) processes provide high contrast but cause swelling, and negative tone development (NTD) processes result in insufficient contrast.
Innovation Solution
The development of resist materials and corresponding lithography techniques that reduce the solubility of unexposed resist layer portions to a developer while maintaining solubility of exposed portions, achieved by incorporating acid labile groups and cross-linkable functional components, which indirectly increase the molecular weight of polymers in unexposed areas, thereby minimizing or eliminating swelling and enhancing pattern fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If positive tone development (PTD) processes are used to achieve sufficient resist contrast, then resist contrast is improved, but resist swelling occurs which degrades LER and LWR
Solution Approach 1:
The patent applies local quality by making the resist layer have different properties in exposed and unexposed regions. Acid labile groups are selectively removed in exposed regions through photoacid generation, while cross-linking occurs primarily in unexposed regions. This creates local solubility differences that enable PTD to achieve high contrast without swelling, as the unexposed regions become cross-linked and resistant to developer penetration.
Solution Approach 2:
The patent uses composite materials by combining multiple functional components in the resist layer: polymers with acid labile groups, photoacid generators, and cross-linking agents. This composite structure allows the resist to exhibit both high contrast development and swelling resistance, as the different components work together to provide contrast enhancement through acid-catalyzed reactions while cross-linking provides structural integrity against developer-induced swelling.
2Manufacturing precision
If negative tone development (NTD) processes are used to minimize resist swelling, then resist swelling is reduced, but resist contrast becomes insufficient
Solution Approach 1:
The patent inverts the conventional NTD approach by using positive tone development chemistry but achieving swelling resistance typically associated with NTD. Instead of relying on NTD's inherent swelling resistance, the patent uses acid-catalyzed cross-linking in unexposed regions to achieve similar swelling protection while maintaining the advantages of PTD for contrast. This inversion allows PTD to achieve both high contrast and swelling control.
Solution Approach 2:
The patent changes the chemical parameters of the resist layer through photoacid-catalyzed reactions. The acid labile groups are selectively removed in exposed regions, and cross-linking is promoted in unexposed regions, fundamentally changing the solubility and structural parameters of the resist. This parameter transformation enables the resist to achieve high contrast development while resisting swelling, combining benefits previously available only from opposing development modes.
3Manufacturing precision
If cross-linking is performed to reduce solubility of unexposed portions, then swelling is minimized, but process complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated process. The photoacid generator, acid labile groups, and cross-linking agents work together in a unified acid-catalyzed reaction system. The same photoacid that removes acid labile groups to enhance contrast also catalyzes cross-linking in unexposed regions to minimize swelling. This merging eliminates the need for separate processing steps, maintaining simplicity while achieving both contrast and swelling control.
Solution Approach 2:
The resist layer performs self-service by using the photoacid generated during exposure to simultaneously drive both contrast enhancement and swelling protection mechanisms. The acid-catalyzed reactions are self-propagating and self-regulating, occurring automatically in the appropriate regions based on the exposure pattern. This self-service approach eliminates the need for external intervention or complex process control, achieving cross-linking and contrast enhancement through the inherent chemistry of the resist system.
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 results in resist patterns with reduced LER/LWR and improved resist contrast, meeting the demands of advanced technology nodes by suppressing swelling and maintaining high patterning fidelity during the development process.
Implementation Method 1
exposing the resist layer to patterned radiation
Implementation Method 2
performing a treatment process on the resist layer to cause cross-linking of acid labile group (ALG) components
Implementation Method 3
performing a development process on the resist layer, thereby forming a patterned resist layer over the workpiece
Data Source
AI summary
The present disclosure provides lithography resist materials and corresponding lithography techniques for improving lithography resolution, in particular, by reducing swelling of resist layers during development. An exemplary lithography method includes performing a treatment process on a resist layer to cause cross-linking of acid labile group components of the resist layer via cross-linkable functional components, performing an exposure process on the resist layer, and performing a development process on the resist layer. In some implementations, the resist layer includes an exposed portion and an unexposed portion after the exposure process, and the treatment process reduces solubility of the unexposed portion to a developer used during the development process by increasing a molecular weight of a polymer in the unexposed portion. The treatment process is performed before or after the exposure process. The treatment process can include performing a thermal treatment and/or an electromagnetic wave treatment to heat the resist layer.