Magnetic Null Debris Routing for EUV Mirror Protection
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Solution Overview
Problem
Current EUV lithography systems face challenges in mitigating debris, particularly high-energy tin ions, which cause damage to the Mo/Si multilayer Bragg reflectors, and existing mitigation strategies using H2 background gas are limited in effectiveness and efficiency.
Innovation Solution
The implementation of a magnetic null configuration using electromagnetic coils or permanent magnets to channel ionized debris along magnetic field lines, avoiding the collection mirror and utilizing a smaller coil to enhance debris routing and control the magnetic null structure and location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If H2 background gas is introduced to mitigate low energy tin ions and splashes, then debris damage to mirrors is reduced, but EUV collection efficiency decreases due to EUV absorption by the background gas
Solution Approach 1:
A magnetic field is introduced as an intermediary mechanism to deflect and redirect ionized debris away from the collection mirror. The magnetic field acts as a mediator that separates the debris mitigation function from the need for background gas, allowing ions to be channeled along magnetic field lines toward designated targets rather than requiring H2 gas to slow and stop them through collisions
Solution Approach 2:
The patent replaces the mechanical/collision-based debris mitigation mechanism (using H2 background gas to slow ions through physical collisions) with a magnetic field-based mechanism. Instead of relying on gas molecules to mechanically interact with and slow ions, the system uses electromagnetic forces to guide and redirect ionized debris along magnetic field lines, substituting a magnetic control system for a gas-based mechanical interaction system
2Object-affected harmful factors
If H2 background gas pressure is increased to mitigate fast high energy tin ions, then ion kinetic energy reduction improves, but EUV absorption by background gas increases significantly
Solution Approach 1:
The magnetic field serves as an intermediary that redirects fast ions before they can travel across the vacuum chamber and deposit their full kinetic energy onto the collection mirror. By introducing magnetic field lines as a guiding mechanism, the system channels high-energy ions along controlled paths toward designated targets, preventing direct impact on sensitive optical components without requiring increased background gas pressure
Solution Approach 2:
The magnetic field configuration performs preliminary action by deflecting and redirecting ionized debris away from the collection mirror trajectory. The magnetic null point and associated field lines are positioned to intercept and guide ions before they can reach the mirror, preventing potential damage in advance rather than relying on background gas to slow them down after they have already traveled across the chamber
3Object-generated harmful factors
If H2 background gas is used to clean tin splashes from mirror surfaces, then deposit removal is achieved, but H ion implantation causes blistering and delamination
Solution Approach 1:
The patent extracts the debris mitigation and cleaning function from the H2 background gas environment. By using magnetic field lines to redirect ionized debris away from the collection mirror, the system removes the need for H2 gas to perform both the slowing/stopping function and the cleaning function, thereby eliminating the harmful side effect of H ion implantation while preserving the beneficial effect of reduced debris accumulation
Solution Approach 2:
The magnetic field configuration converts the potentially harmful direct impact of ionized debris on the mirror into a beneficial redirection toward designated targets. By channeling ions along magnetic field lines, the system transforms what would be destructive impacts into controlled trajectories that protect the mirror while still allowing the debris to be managed and eventually removed through other means
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 effectively reduces debris accumulation on the mirror by guiding ions away from sensitive components, potentially extending the lifetime of EUV systems and improving collection efficiency without trapping particles, allowing for a more efficient and minimal buffer gas operation.
Implementation Method 1
generating one or more three-dimensional magnetic nulls at one or more points, including those at which ions are created by an EUV system, such that substantially all ionized debris generated by the EUV system is channeled along magnetic field lines
Implementation Method 2
substantially all ionized debris generated by the EUV system is channeled along magnetic field lines
Implementation Method 3
channeled along magnetic field lines, substantially aligned with a fan plane or a spine line defined by magnetic fields that form the one or more three-dimensional magnetic nulls
Implementation Method 4
forming the one or more three-dimensional magnetic nulls with magnetic fields generated by a plurality of electromagnetic coils
Data Source
AI summary
Disclosed is a method of debris mitigation in laser produced plasma EUV light sources. The method describes a class of magnetic field configurations which exhausts debris away from sensitive components of the EUV device. This class contains a large range of configurations that may be suited and tuned to specific application requirements with a high degree of flexibility and can be generated by coils that are located away from the light collection cone.