EUV Light Source Cooling Element for Thermal Stability
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Solution Overview
Problem
High EUV light loss at each mirror in the optical train of EUV lithography systems due to high absorption of most materials, and increased temperature and pressure issues when increasing laser power in LPP-EUV light sources with rotating crucibles, leading to instability in EUV light output.
Innovation Solution
Incorporating a cooling element, such as a cooling plate or shim, secured to a stationary component near the rotating crucible, which uses coolant fluid to absorb and dissipate thermal energy from the EUV light-emitting plasma, thereby maintaining temperature stability and reducing pressure in the vacuum chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser power is increased in LPP-EUV light sources, then EUV light brightness is improved, but temperature and pressure increase causing instability
Solution Approach 1:
The patent extracts the thermal management function by introducing a separate cooling element (cooling plate or shim) that is spatially separated from the laser interaction region. This cooling element is positioned to receive and dissipate thermal energy from the plasma, effectively removing heat from the system without interfering with the EUV light generation process. The cooling element is secured to a stationary component near the rotating crucible, allowing it to selectively manage thermal loads while maintaining optical performance.
2Illumination intensity
If laser power is increased in LPP-EUV light sources, then EUV light brightness is improved, but pressure increases causing instability
Solution Approach 1:
The patent extracts the pressure management function through the cooling element that dissipates thermal energy. By removing excess heat from the plasma interaction region, the cooling element prevents thermal expansion and gas pressure buildup in the vacuum chamber. The cooling element's thermal conduction path effectively decouples the laser power input from pressure increases, allowing high brightness operation without pressure-induced instability.
3Stability of the object's composition
If cooling element is added to reduce temperature, then temperature stability is improved, but device complexity increases
Solution Approach 1:
The cooling element is designed to serve multiple functions simultaneously: it cools the plasma interaction region, supports the rotating crucible assembly, and maintains structural integrity of the vacuum chamber components. By integrating cooling functionality into an existing structural component (the stationary component near the crucible), the patent avoids adding separate complex cooling systems. The cooling element acts as both a thermal management device and a structural support element, reducing overall device complexity.
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 cooling element effectively reduces temperature and pressure fluctuations, enhancing the stability and brightness of the EUV light output even at higher laser powers, ensuring consistent performance in EUV lithography.
Implementation Method 1
a cooling element... which uses coolant fluid to absorb and dissipate thermal energy from the EUV light-emitting plasma
Implementation Method 2
coolant fluid to absorb and dissipate thermal energy
Implementation Method 3
a laser beam impinges on a suitable liquid metal, such as liquid tin, and the resulting liquid metal plasma emits EUV light
Implementation Method 4
the resulting liquid metal plasma emits EUV light
Data Source
AI summary
A laser produced plasma (LPP)-extreme ultraviolet (EUV) light source includes a vacuum chamber, a rotatable crucible disposed in the vacuum chamber with an annular inner surface for carrying a liquid metal, and a laser arranged to apply laser light to the liquid metal carried on the annular inner surface of the rotatable crucible to cause the liquid metal to emit EUV light. The LPP-EUV light source further includes a stationary component disposed in the vacuum chamber and positioned proximate to the annular inner surface of the rotatable crucible or surrounding the rotatable crucible, a coolant fluid delivery inlet or nozzle, and a cooling element secured with the stationary component and including a feature configured to operatively couple with coolant fluid delivered by the coolant fluid delivery inlet or nozzle.