Dual Pellicle EUV Mask Protection and Transmission
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Solution Overview
Problem
Extreme ultraviolet (EUV) masks are highly susceptible to damage during exposure and inspection due to the need for pellicle removal, which compromises their protective integrity and compatibility with different wavelength ranges.
Innovation Solution
Implementing a dual-pellicle system where a stronger, thicker organic polymer pellicle is used for protection during handling and inspection, and a thinner, silicon-based pellicle is used during EUV exposure, allowing EUV wavelengths to pass while minimizing damage from longer wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single pellicle is used on EUV masks, then the mask can be protected during handling and inspection, but the mask becomes highly susceptible to damage during exposure because the pellicle must be removed to allow EUV wavelengths to pass
Solution Approach 1:
The protective pellicle system is segmented into two distinct pellicles: a first pellicle (thicker, stronger organic polymer) for protection during handling, transport, and inspection; and a second pellicle (thinner, EUV-transparent material) for use during exposure. This segmentation allows each pellicle to be optimized for its specific function, resolving the contradiction between protection and exposure compatibility.
Solution Approach 2:
The pellicle configuration is made dynamic by replacing the first pellicle with the second pellicle before exposure, and replacing the second pellicle with the first pellicle after exposure. This dynamic switching allows the system to adapt to different operational requirements, providing strong protection when needed and EUV transparency when needed.
2Strength
If a thicker, stronger organic polymer pellicle is used to protect the EUV mask, then handling and inspection reliability improves, but EUV wavelengths cannot pass through effectively
Solution Approach 1:
The pellicle protection system is divided into two specialized components: the first pellicle made of thicker organic polymer material optimized for mechanical strength and protection during handling; and the second pellicle made of thinner material optimized for EUV wavelength transmission during exposure. Each segment is optimized for its specific function.
Solution Approach 2:
Different pellicle materials and thicknesses are applied locally for different operational phases: the stronger first pellicle is used during handling, transport, and inspection phases; the thinner second pellicle is used during the exposure phase. This local optimization resolves the contradiction between strength and light transmission.
3Use of energy by moving object
If the pellicle is removed during exposure to allow EUV light transmission, then exposure quality improves, but the mask becomes highly susceptible to damage
Solution Approach 1:
The second pellicle acts as an intermediary during the exposure process - it is thin enough to allow EUV wavelengths to pass through effectively for high-quality exposure, while still providing a degree of protection to the mask. After exposure, the first pellicle is reinstated as the primary protective intermediary during handling and inspection.
Solution Approach 2:
The protective pellicle configuration dynamically changes during the exposure workflow: the first pellicle is replaced with the thinner second pellicle before exposure to enable EUV transmission, and then the second pellicle is replaced with the first pellicle after exposure to restore full protection during subsequent handling operations.
4Use of energy by moving object
If a single thin pellicle is used to allow EUV wavelengths to pass, then exposure process improves, but the pellicle is easily damaged during handling and inspection
Solution Approach 1:
The pellicle system is segmented into two specialized layers: the first pellicle provides mechanical strength and durability for handling and inspection; the second pellicle provides EUV transparency for exposure. This segmentation allows each layer to be optimized for its specific function without compromise.
Solution Approach 2:
The protective system uses composite material strategy by combining two different pellicle materials: a stronger organic polymer material for the first pellicle that provides mechanical durability; and a thinner EUV-transparent material for the second pellicle that enables light transmission. The composite approach allows both strength and transparency requirements to be met.
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 protection and reliability of EUV masks by reducing damage risk and improving handling and inspection processes, allowing for extended mask lifetime and efficient pellicle management.
Implementation Method 1
The first pellicle only allows wavelengths of electromagnetic radiation longer than EUV wavelengths to pass
Implementation Method 2
The second pellicle allows EUV wavelengths (e.g., shorter than 15 nm) of electromagnetic radiation to pass
Data Source
AI summary
An optical mask has a first pellicle attached. The optical mask is inspected with the first pellicle in place using first wavelengths of electromagnetic radiation. The first pellicle is replaced with a second pellicle. The first pellicle only allows the first wavelengths of electromagnetic radiation to pass, and the second pellicle allows second wavelengths that are shorter than the first wavelengths to pass. A photoresist is exposed using the optical mask with the second pellicle in place. The second pellicle is replaced with the first pellicle. The optical mask is again inspected with the first pellicle in place using the first wavelengths of electromagnetic radiation.