Immersion Lithography Overcoating Composition for Photoresist Migration Control
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Solution Overview
Problem
Current immersion lithography systems lack reliable and convenient photoresist and imaging processes, and there is a need for new materials and processes to achieve smaller feature sizes in semiconductor manufacturing driven by Moore's law.
Innovation Solution
Development of overcoating compositions comprising copolymers or terpolymers with hydrophilic groups and reactive moieties, applied above a photoresist layer, which inhibit the migration of photoresist components into immersion fluids and enhance lithographic performance by reducing acid or organic material in the immersion fluid, thereby improving resolution and pattern transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If immersion lithography is used to increase numerical aperture and achieve smaller feature sizes, then resolution is improved, but photoresist components migrate into the immersion fluid causing contamination and process reliability deterioration
Solution Approach 1:
A top coat layer is introduced as an intermediary barrier between the photoresist and the immersion fluid. This top coat prevents photoresist components from migrating into the immersion fluid while allowing the immersion lithography process to proceed with improved resolution. The top coat acts as a protective mediator that maintains process reliability without compromising the resolution benefits of immersion lithography.
Solution Approach 2:
The photoresist system is segmented into multiple functional layers: the base photoresist layer for pattern formation and a top coat layer for protection and fluid barrier functions. This segmentation allows each layer to be optimized independently - the photoresist for sensitivity and pattern fidelity, and the top coat for preventing contamination of the immersion fluid.
2Manufacturing precision
If shorter wavelengths of light are used to achieve smaller feature sizes, then resolution is improved, but material transparency becomes difficult to obtain below 193 nm
Solution Approach 1:
The top coat serves as an intermediary protective layer that enables the use of 193 nm wavelength light by preventing photoresist degradation and contamination of the immersion fluid. This allows the system to operate at the practical wavelength limit where materials are still available and transparent, without requiring shorter wavelengths that would demand materials below 193 nm.
Solution Approach 2:
The system changes the chemical composition parameters of the top coat layer to achieve optimal transparency at 193 nm wavelength while maintaining barrier properties. By carefully selecting polymers and additives with appropriate molecular structures and functional groups, the top coat achieves both optical transparency and protective functionality.
3Reliability
If a top coat layer is applied to prevent photoresist migration into immersion fluid, then process reliability is improved, but additional processing steps and material complexity are introduced
Solution Approach 1:
The top coat is formulated as a homogeneous solution containing specific polymers (such as polyhydroxystyrene or carboxy-containing polymers) and additives in controlled concentrations. This homogeneous composition ensures uniform application and consistent protective properties across the entire photoresist layer, simplifying the coating process and ensuring reliable performance.
Solution Approach 2:
The top coat utilizes composite material science by combining multiple functional components - polymers for structural integrity and barrier properties, surfactants for wetting and uniform coating, and other additives for optimized performance. This composite approach achieves multiple functions in a single layer, reducing the need for additional separate processing steps.
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 overcoating compositions effectively reduce the amount of photoresist material in the immersion fluid, leading to improved resolution and pattern transfer in immersion lithography, enabling the use of sub-300 nm wavelengths and facilitating the production of microelectronic devices with smaller feature sizes.
Implementation Method 1
The overcoating compositions effectively reduce the amount of photoresist material in the immersion fluid
Implementation Method 2
The overcoating compositions effectively reduce the amount of photoresist material in the immersion fluid
Implementation Method 3
Immersion lithography employs a relatively high refractive index fluid between the last surface of an imaging device and the first surface on a wafer to focus more light into the film
Data Source
AI summary
Overcoating layer compositions are provided that are applied above a photoresist composition including for immersion lithography processing as well as non-immersion imaging.