Metal Hardmask Passivation for EUV Lithography Resolution
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Solution Overview
Problem
In integrated circuit fabrication, the interface between a metal-containing hardmask layer and the EUV photoresist in trilayer photoresist stacks experiences issues such as conjugates of metal-hydroxyl groups, leading to undesirable pattern profiles like undercuts and footings, which degrade the imaging resolution and require high baking temperatures that can cause contamination.
Innovation Solution
A method involving a metal-containing silicon-based hardmask layer treated at temperatures between 100° C and 300° C with catalysts or additives like capping agents and chelating ligands to reduce metal-hydroxyl group conjugates, forming a passivated surface that improves the interface with the photoresist, allowing for lower exposure energies and reduced line edge roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high baking temperatures are used to treat the metal-containing hardmask layer, then the metal-hydroxyl group conjugates are reduced, but contamination risks increase and manufacturing complexity increases
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>400°C) to a lower range (100-300°C), and introduces chemical additives (capping agents and chelating ligands) to modify the chemical environment. This parameter change allows the metal-hydroxyl group conjugates to be reduced effectively at lower temperatures, thereby reducing contamination risks while maintaining pattern dimension accuracy
Solution Approach 2:
The patent introduces capping agents and chelating ligands as intermediary substances that mediate between the metal-containing hardmask layer and the EUV photoresist. These intermediaries bind to the metal-hydroxyl groups, preventing their harmful conjugation effects at the interface, and enable effective treatment at lower temperatures without causing contamination
2Strength
If the thickness of the photoresist layer is increased to provide sufficient etch resistance, then the resistance to etch or ion implantation is improved, but the depth of focus degrades and imaging resolution worsens
Solution Approach 1:
The patent segments the photoresist system into multiple layers: a bottom anti-reflective coating (BARC) layer, a main photoresist layer, and a middle layer. This segmentation allows each layer to have optimized thickness for its specific function - the BARC layer provides etch resistance while the main photoresist layer maintains imaging resolution, and the middle layer addresses interface issues between the hardmask and photoresist
Solution Approach 2:
The patent uses a composite multi-layer structure consisting of different materials with complementary properties. The BARC layer (e.g., silicon-containing polymer) provides etch resistance, the photoresist layer (e.g., chemically amplified resist) provides imaging capability, and the middle layer (metal-containing) addresses interface compatibility. This composite structure achieves both sufficient etch resistance and high imaging resolution
3Manufacturing precision
If conventional high temperature baking is used to treat the metal-containing hardmask layer, then the metal-hydroxyl group conjugates are reduced, but the process complexity and energy consumption increase
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>400°C) to a lower range (100-300°C), and introduces chemical additives (capping agents and chelating ligands) to modify the chemical environment. This parameter change allows the metal-hydroxyl group conjugates to be reduced effectively at lower temperatures, thereby reducing contamination risks while maintaining pattern dimension accuracy
Solution Approach 2:
The patent replaces the purely thermal mechanism (high-temperature baking) with a chemical mechanism involving capping agents and chelating ligands. This substitution allows the treatment to proceed at lower temperatures through chemical reactions rather than relying solely on thermal energy, reducing energy consumption while achieving the same or better results
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 enhances the sensitivity of the photoresist to EUV radiation, decreases the optimum exposure energy by up to 15%, and avoids the need for high-temperature baking, thereby improving pattern dimension accuracy and reducing contamination risks.
Implementation Method 1
treating the metal-containing layer at temperatures between 100° C and 300° C to reduce conjugates of metal-hydroxyl groups within or on a surface of the metal-containing layer
Implementation Method 2
enhances the sensitivity of the photoresist to EUV radiation
Data Source
AI summary
A lithography method is provided in accordance with some embodiments. The lithography method includes forming a metal-containing layer on a substrate, the metal-containing layer including a plurality of conjugates of metal-hydroxyl groups; treating the metal-containing layer at temperature that is lower than about 300° C. thereby causing a condensation reaction involving the plurality of conjugates of metal-hydroxyl groups; forming a patterned photosensitive layer on the treated metal-containing layer; and developing the patterned photosensitive layer so as to allow at least about 6% decrease of optimum exposure (Eop).