Iodized Positive Resist Composition for EUV Lithography Edge Roughness Control
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Solution Overview
Problem
Current EUV lithography technologies face challenges in achieving high resolution and reduced edge roughness and size variation due to variations in photon number, leading to degraded line edge roughness (LER) and critical dimension uniformity (CDU) in pattern formation, especially with iodized polymers that have low EUV absorption and poor dissolution contrast.
Innovation Solution
A positive resist composition is developed using a base polymer with recurring units containing an imide group and iodine-substituted aromatic rings, combined with recurring units having carboxyl or phenolic hydroxyl groups with acid labile substitutions, which enhances light absorption, acid generation efficiency, and minimizes acid diffusion, thereby improving sensitivity, resolution, and dissolution contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If iodized polymers are used to increase EUV absorption, then sensitivity and acid generation increase, but dissolution contrast lowers and LWR/CDU degrade
Solution Approach 1:
The patent uses a composite polymer structure combining iodized aromatic rings for EUV absorption with carboxyl/phenolic hydroxyl groups for dissolution contrast. The polymer comprises recurring units with imide groups having iodine-substituted aromatic rings bonded thereto, combined with recurring units having carboxyl or phenolic hydroxyl groups with acid labile substitutions, creating a material that achieves both high absorption and high dissolution contrast.
Solution Approach 2:
The patent applies local quality by positioning different functional groups at specific locations within the polymer structure. The iodized aromatic rings are placed to maximize EUV absorption, while carboxyl or phenolic hydroxyl groups with acid labile substitutions are positioned to provide dissolution contrast and minimize acid diffusion to unexposed regions.
2Manufacturing precision
If acid diffusion is suppressed to prevent image blur, then resolution improves, but sensitivity may be reduced
Solution Approach 1:
The patent introduces acid labile groups as intermediaries between the acid generator and the polymer backbone. These groups act as a buffer that allows acid to be generated and localized without excessive diffusion, maintaining both sensitivity (through efficient acid generation) and resolution (through controlled acid distribution). The acid labile groups are cleaved by generated acid to create soluble regions while preventing acid from diffusing to unexposed areas.
3Manufacturing precision
If photon number is increased to reduce variation, then LWR and CDU improve, but more complex multi-patterning processes are required
Solution Approach 1:
The patent changes the optical and chemical parameters of the resist material by incorporating iodized aromatic rings that have high absorption cross-sections for EUV photons. This parameter change allows the resist to be more sensitive to lower photon doses, reducing the impact of photon number variation and improving CDU without requiring complex multi-patterning processes.
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, reduced edge roughness, and improved critical dimension uniformity, making it suitable for fine pattern formation in VLSIs and photomasks with enhanced dissolution contrast and acid diffusion control.
Implementation Method 1
since the solubility of the iodized polymer in an alkaline aqueous solution as the developer is extremely low, the dissolution contrast lowers, and LWR and CDU are degraded. It is desired to develop a resist material having sufficient light absorption and a high dissolution contrast.
Implementation Method 2
the number of photons available with EUV exposure is 1/14 of that of ArF exposure. In the EUV lithography, the phenomenon that the edge roughness (LER, LWR) of line patterns or the critical dimension uniformity (CDU) of hole patterns is degraded by a variation of photon number is considered a problem.
Implementation Method 3
recurring units having a carboxyl or phenolic hydroxyl group whose hydrogen is substituted by an acid labile group
Data Source
AI summary
A positive resist composition comprising a base polymer comprising recurring units (a) containing an imide group having an iodized aromatic group bonded thereto and recurring units (b1) having an acid labile group-substituted carboxyl group and/or recurring units (b2) having an acid labile group-substituted phenolic hydroxyl group has a high sensitivity and resolution and forms a pattern of good profile with reduced edge roughness and size variation.