Target Supply Heater Control for Uniform EUV Droplet Solidification
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Solution Overview
Problem
In existing target supply devices, the solidification and shrinkage of target substances during cooling are non-uniform, leading to gaps that can cause oxidation and hinder the formation of droplets, affecting the output of extreme ultraviolet light generation.
Innovation Solution
A target supply device with a temperature control processor that sets the intermediate portion heater to a temperature lower than the melting point of the target substance while maintaining the main and sub-heaters above the melting point, controlling the temperature lowering rates to minimize gaps and oxidation during solidification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the target substance is cooled uniformly during solidification, then the solidification process is simplified, but non-uniform solidification and shrinkage occur leading to gaps and oxidation
Solution Approach 1:
The cooling process is segmented into two distinct phases: first cooling the intermediate portion below the melting point to induce solidification and shrinkage, then cooling the tank main body and output portion while maintaining the intermediate portion at a higher temperature. This segmentation prevents gap formation and oxidation by controlling the solidification sequence.
Solution Approach 2:
The intermediate portion is cooled below the melting point before cooling the tank main body and output portion. This preliminary action causes the intermediate portion to solidify first, creating a shrinkage that draws the molten target substance toward the intermediate portion, preventing gap formation and oxidation.
2Productivity
If the temperature is lowered rapidly to stop output, then productivity is improved, but gaps form and oxidation occurs
Solution Approach 1:
The temperature lowering is segmented into different rates for different portions: the intermediate portion is cooled rapidly below the melting point to stop output quickly, while the tank main body and output portion are cooled more slowly to prevent gap formation and oxidation.
Solution Approach 2:
The intermediate portion is cooled below the melting point before cooling the tank main body and output portion. This preliminary rapid cooling stops the output quickly, while the subsequent slower cooling of other portions prevents oxidation and gap formation.
3Device complexity
If all heater temperatures are lowered equally, then the control process is simplified, but non-uniform solidification occurs causing gaps and oxidation
Solution Approach 1:
Different temperature lowering control is applied to different portions: the intermediate portion heater is controlled to lower the temperature below the melting point, while the tank main body heater and output portion heater are controlled to maintain temperatures above the melting point during the initial cooling phase. This local differentiation ensures uniform solidification without gaps or oxidation.
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 ensures uniform solidification and minimizes residual oxygen, enhancing droplet formation and reducing oxidation issues, thereby improving the efficiency of extreme ultraviolet light generation.
Implementation Method 1
a first main heater configured to heat the tank main body portion
Implementation Method 2
a first sub-heater configured to heat the output portion
Implementation Method 3
an intermediate portion heater configured to heat the intermediate portion
Implementation Method 4
the target substance is cooled down, the molten target substance is shrunk in the intermediate portion in accordance with solidification shrinkage
Data Source
AI summary
A target supply device includes a tank main body portion containing a target substance; an output portion outputting the target substance; an intermediate portion located between the tank main body portion and the output portion; a first main heater heating the tank main body portion; a first sub-heater heating the output portion; an intermediate portion heater heating the intermediate portion; and a temperature control processor configured to perform temperature lowering control of the first main heater, the first sub-heater, and the intermediate portion heater after output of the target substance is stopped. The temperature control processor sets, in the temperature lowering control, a temperature of the intermediate portion heater to a temperature lower than a melting point of the target substance while setting each of a temperature of the first main heater and a temperature of the first sub-heater to a temperature higher than the melting point.