Cryogenic Droplet EUV Light Source for Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-power EUV light sources for photolithography have high operating costs and require frequent maintenance due to metal byproducts fouling optics and vacuum chambers, and inefficiencies in converting cryogenic droplets to plasma result in attenuated EUV light and excess gas injection.
Innovation Solution
A laser-produced plasma EUV light source with a driver laser focusing a beam onto a target spot smaller than 100 µm, using a piezoelectric actuator to modulate cryogenic liquid droplet formation and acceleration through a triple point chamber, reducing droplet evaporation and increasing conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-power laser produced plasma EUV light source is used to achieve sufficient photolithographic throughput, then EUV light output is improved (100 W or above), but energy consumption increases enormously (in excess of 200 kW at the wall)
Solution Approach 1:
The patent changes the physical state of the target material from solid metal to cryogenic liquid droplets, and modifies the droplet generation parameters (size, spacing, velocity) to optimize plasma conversion efficiency. This allows achieving adequate EUV output with lower laser power requirements
Solution Approach 2:
The patent uses precisely controlled cryogenic liquid droplets that are injected at optimal rates and positions to ensure each droplet is effectively converted to plasma by the laser pulse, avoiding both insufficient conversion and excessive gas injection that would attenuate EUV light
2Power
If metal target material (tin or other metals) is used in laser produced plasma EUV light source, then EUV light generation is achieved, but metal byproducts foul the optics and vacuum chamber requiring difficult and costly maintenance
Solution Approach 1:
The patent changes the target material from solid metal to cryogenic liquid (such as xenon or other noble gases), fundamentally altering the plasma generation process to eliminate metal particulate production while maintaining EUV light generation capability
Solution Approach 2:
The patent uses consumable cryogenic liquid droplets that are continuously supplied and converted to plasma, eliminating the need for durable metal targets that produce fouling byproducts. The cryogenic liquid is inexpensive and leaves no persistent contaminants
3Reliability
If droplets are injected at higher rate to increase the odds that driver laser pulse strikes a droplet, then plasma conversion reliability is improved, but excess gas attenuates the EUV light generated
Solution Approach 1:
The patent employs dynamic control of droplet injection timing, velocity, and positioning to precisely synchronize droplet arrival with laser pulse timing. This ensures reliable plasma conversion while maintaining optimal droplet spacing to minimize EUV attenuation
Solution Approach 2:
The system uses feedback control to monitor droplet-laser interaction and adjust injection parameters in real-time, optimizing the balance between ensuring laser-droplet intersection and preventing excessive gas density that would attenuate EUV light
4Power
If cryogenic droplets are used as driver laser target, then EUV light generation is achieved, but not all droplets are successfully converted to plasma due to timing and aiming inaccuracies
Solution Approach 1:
The patent uses dynamic adjustment of droplet injection timing, velocity, and spatial positioning to ensure precise synchronization with the laser pulse arrival, maximizing the probability that each droplet is successfully converted to plasma
Solution Approach 2:
The patent replaces passive droplet generation with an actively controlled system using piezoelectric actuators to precisely modulate droplet formation and delivery, replacing less accurate mechanical timing and positioning methods
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 reduces operational costs, minimizes maintenance, and enhances EUV light output by efficiently using the driver laser and reducing gas attenuation, achieving lower power consumption and higher conversion rates.
Implementation Method 1
a piezoelectric actuator attached to a nozzle tip which modulates a flow velocity of target material through the nozzle tip to form droplets of the target material
Implementation Method 2
a driver laser arranged to produce a laser pulse... a set of focusing optics arranged to focus the laser pulse produced by the driver laser onto a target spot
Implementation Method 3
the driver laser used to generate the plasma... which plasma then emits radiation in the EUV portion of electromagnetic spectrum
Implementation Method 4
a set of focusing optics arranged to focus the laser pulse produced by the driver laser onto a target spot within the vacuum chamber with a beam target diameter of less than 100 μm
Implementation Method 5
a set of collector optics arranged to focus a quantity of EUV light generated when the target material is exposed to the laser pulse at the target spot onto an intermediate focus spot
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3b
AI summary
An apparatus for generating extreme ultra-violet (EUV) light for use in a lithography inspection tool, comprising a drive laser arranged to produce a laser pulse, a vacuum chamber, a set of focusing optics arranged to focus the laser pulse produced by the drive laser onto a target spot within the vacuum chamber with a beam target diameter of less than 100 μιη, a target material generator arranged to deliver an amount of a target material to the target spot within the vacuum chamber, and a set of collector optics arranged to focus a quantity of EUV light generated when the amount of the target material is exposed to the laser pulse at the target spot onto an intermediate focus spot.