EUV Lithography Illumination System Contamination Control
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Solution Overview
Problem
Extreme ultraviolet (EUV) radiation sources, such as laser-produced plasma (LPP) sources, produce contaminants like HBr, which contaminate the illumination system in lithographic apparatuses due to high pressure differences, affecting the quality of pattern printing in microelectronics manufacturing.
Innovation Solution
A lithographic apparatus is designed with a suppression flow system and pumping system to prevent contamination by providing a gas flow, using gases like H2, He, Ne, or Ar, and a flow distributing structure to enhance flow homogeneity, and a pumping system to manage gas pressure, ensuring that contamination particles are suppressed from passing through the radiation aperture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser-produced plasma source is used to generate EUV radiation, then the radiation wavelength is shortened to enable small feature printing, but contamination (such as HBr) is produced that enters and contaminates the illumination system
Solution Approach 1:
The system is divided into separate pressure zones: the radiation source operates at high pressure (10^-3 to 10^-1 Pa) while the illumination system operates at low pressure (10^-6 to 10^-8 Pa). The aperture couples these zones, allowing radiation transmission while the pressure gradient and gas flow control prevent contamination migration from the source to the illumination system.
Solution Approach 2:
A gas flow (H2, He, Ne, or Ar) acts as an intermediary medium through the aperture. This gas flow is controlled to move from the illumination system side toward the source side, creating a protective barrier that prevents contamination particles from entering the illumination system while allowing EUV radiation to pass through.
2Power
If the pressure in the radiation source is increased to improve source performance, then radiation output is enhanced, but contamination is more likely to enter the illumination system
Solution Approach 1:
The system establishes a controlled pressure gradient between the source and illumination system. The aperture creates a pressure differential that, when combined with controlled gas flow, establishes a stable interface where high pressure exists in the source region but contamination is prevented from migrating to the low pressure illumination region through the equipotential gas flow barrier.
Solution Approach 2:
Gas flow (pneumatic control) is used to manage the interface between the high-pressure radiation source and low-pressure illumination system. By controlling the flow of inert gas through the aperture, the system uses pneumatic pressure management to prevent contamination ingress while maintaining the necessary pressure differential for source performance.
3Illumination intensity
If an aperture is provided in the illumination system wall to allow radiation entry, then radiation transmission is enabled, but contamination particles can pass through the aperture into the illumination system
Solution Approach 1:
The system changes the parameter of gas flow velocity and direction through the aperture. By controlling the gas flow to move from the illumination side toward the source side at appropriate velocities, the aperture transforms from a potential contamination pathway into a controlled interface where radiation passes through but contamination particles are repelled by the opposing gas flow.
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 effectively reduces contamination in the illumination system, maintaining the cleanliness and efficiency of the lithographic process, thereby improving the precision and reliability of feature printing in microelectronics manufacturing.
Implementation Method 1
a pumping system configured to pump away gas
Implementation Method 2
the pressure in an EUV radiation source is generally high relative to the pressure in the lithographic apparatus or another part of the lithographic apparatus if the radiation source is part of the lithographic apparatus, the contamination will tend to enter and contaminate an illumination system
Data Source
AI summary
A lithographic apparatus is arranged to project a pattern from a patterning device onto a substrate is disclosed. The lithographic apparatus includes an illumination system and an outlet connected to a pumping system to pump away gas from between an inner wall and outer wall of the illumination system or, if a radiation source is present, between the inner wall of the illumination system and an inner wall of the radiation source.