EUV Tin Target Deoxidation via Hydrogen Flow
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Solution Overview
Problem
High purity tin used in EUV light sources often contains oxygen beyond its solubility limit, leading to the formation of tin oxide particles that clog nozzles and cause equipment failure, as existing purification processes are not designed to remove oxygen effectively.
Innovation Solution
A system and method involving a furnace with a gas input and exhaust network, using hydrogen and argon gas mixtures to deoxidize molten tin by forming water vapor, which is carried away, reducing oxygen concentration to below the solubility limit, thereby preventing nozzle clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If commercially pure tin is used, then the manufacturing cost is reduced and ease of manufacture is improved, but oxygen concentration exceeds solubility limit causing tin oxide particle formation and nozzle clogging
Solution Approach 1:
The patent applies preliminary action by performing deoxidation treatment on the tin target material before it is used in the droplet generator. The tin is heated to melt it, then hydrogen gas is introduced to react with excess oxygen and form water vapor that is removed by vacuum pumping. This preliminary purification prevents oxide particle formation during subsequent droplet generation operations, ensuring reliable nozzle operation without requiring more expensive pre-purified starting material.
Solution Approach 2:
The patent applies parameter changes by controlling the chemical composition parameters through hydrogen deoxidation. By introducing hydrogen gas and controlling the vacuum conditions, the oxygen concentration in the molten tin is reduced below the solubility limit. This parameter change (oxygen concentration) prevents the formation of tin oxide particles while maintaining the ease of using commercially pure starting material.
2Manufacturing precision
If existing purification processes are used, then metallic impurities are removed effectively, but oxygen removal is insufficient leading to tin oxide particle formation
Solution Approach 1:
The patent converts the harmful effect of excess oxygen into a beneficial process by using hydrogen to react with the oxygen. The hydrogen deoxidation process transforms the harmful oxygen into water vapor, which is then easily removed under vacuum conditions. This approach turns the problematic oxygen content in commercially pure tin into a controlled reaction that actually improves the material purity and prevents oxide particle formation.
Solution Approach 2:
The patent introduces hydrogen gas as an intermediary substance to facilitate oxygen removal. The hydrogen acts as a mediator that reacts with oxygen to form water vapor, which can then be removed by the vacuum system. This intermediary approach enables effective oxygen removal without requiring complex direct oxygen extraction methods, thereby eliminating tin oxide particle formation while maintaining manufacturing simplicity.
3Reliability
If high purity tin with low oxygen content is used, then nozzle clogging is prevented, but the manufacturing cost increases and ease of manufacture decreases
Solution Approach 1:
The patent applies self-service by enabling the tin target material to undergo self-purification through in-situ deoxidation. Rather than requiring externally pre-purified high-purity tin, the system uses hydrogen gas introduction and vacuum pumping to allow the molten tin to self-remove excess oxygen before use. This self-service approach achieves reliable low-oxygen tin while maintaining ease of manufacture with commercially pure starting material.
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 method significantly reduces oxygen levels in tin, preventing nozzle clogging and ensuring the reliability of EUV light sources by maintaining the target material at high temperatures and flowing hydrogen over its surface to form water vapor, effectively removing excess oxygen.
Implementation Method 1
flowing a gas containing hydrogen over a free surface of the molten target material, and measuring a concentration of water vapor in the gas exiting the vessel
Implementation Method 2
The furnace has at least one heater configured to heat the central region thereof in a substantially uniform manner
Implementation Method 3
The closure device is configured to form a seal having vacuum and pressure capability
Implementation Method 4
flowing a gas containing hydrogen over a free surface of the molten target material
Data Source
AI summary
A deoxidation system for purifying target material for an EUV light source includes a furnace having a central region and a heater for heating the central region in a uniform manner. A vessel is inserted in the central region of the furnace, and a crucible is disposed within the vessel. A closure device covers an open end of the vessel to form a seal having vacuum and pressure capability. The system also includes a gas input tube, a gas exhaust tube, and a vacuum port. A gas supply network is coupled in flow communication with an end of the gas input tube and a gas supply network is coupled in flow communication with an end of the gas exhaust tube. A vacuum network is coupled in flow communication with one end of the vacuum port. A method and apparatus for purifying target material also are described.