EUV Pellicle Frame Holes for Airflow and Pressure Equalization
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Solution Overview
Problem
The challenge in EUV lithography is the difficulty in fabricating a pellicle with sufficient EUV transmission and mounting it on an EUV mask without damaging the fragile membrane due to air pressure differences and flow issues between the mask and the pellicle.
Innovation Solution
Forming holes in the frame and membrane of the EUV mask pellicle to enhance airflow and using a sacrificial layer with pillars for support, allowing for improved mounting and protection from pressure variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a thin membrane is used to create a pellicle with high EUV transmission, then the EUV transmission is improved, but the membrane becomes very fragile and difficult to mount
Solution Approach 1:
The patent uses a thin membrane (25nm thick) made of silicon nitride or other EUV-transparent materials to achieve high EUV transmission (86-90%). The membrane is supported by a rigid frame structure with holes, combining the advantages of thin films (high transmission) with structural support (preventing fragility).
Solution Approach 2:
The pellicle structure combines multiple materials: a thin EUV-transparent membrane (silicon nitride, silicon oxide, or organic materials) supported by a rigid frame (aluminum, stainless steel, or other metals). This composite structure achieves both high EUV transmission and mechanical strength for mounting.
2Ease of manufacture
If the air flow between the inside of the closed area and outside the closed area is not smooth and the air pressure difference is large, then the mounting process is simpler, but the thin membrane may be damaged
Solution Approach 1:
The frame structure includes holes ( openings) that allow smooth air flow between the interior and exterior of the closed area. The holes have diameters of 1-10 micrometers and are distributed throughout the frame, enabling pressure equalization during mounting and shipping while maintaining structural support for the membrane.
Solution Approach 2:
The frame with pre-formed holes provides pressure equalization pathways before the membrane can be damaged by pressure differences. This preventive design protects the fragile membrane during mounting, shipping, and operation by allowing gradual pressure equalization.
3Reliability
If holes are formed in the frame, then air flow is improved and membrane protection is enhanced, but the device complexity increases
Solution Approach 1:
The frame structure is segmented with multiple holes distributed throughout, breaking the solid frame into a perforated structure. This segmentation improves air flow and pressure equalization while maintaining overall structural integrity through the distributed hole pattern rather than requiring complex internal mechanisms.
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 solution ensures the pellicle is not damaged during mounting and maintains sufficient airflow, addressing the fragility and pressure issues, thereby improving the reliability and durability of the EUV mask pellicle.
Implementation Method 1
forming the holes to improve air flow between a space enclosed between the mask and the pellicle and a space outside the mask and pellicle
Data Source
AI summary
A method of forming an improved EUV mask and pellicle with airflow between the area enclosed by the mask and pellicle and the area outside the mask and pellicle and the resulting device are disclosed. Embodiments include forming a frame around a patterned area on an EUV mask; forming a membrane over the frame; and forming holes in the frame.