EUV Lithography Residual Gas Analyzer Ion Trap Detection
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Solution Overview
Problem
Existing EUV lithography apparatuses face challenges in detecting very small quantities of contaminating substances, particularly at high residual gas pressures, as conventional residual gas analyzers struggle to normalize ion currents and detect ions with extremely low partial pressures.
Innovation Solution
Incorporating a storage device, such as an ion trap, into the residual gas analyzer to accumulate and isolate contaminating substances, enhancing detection sensitivity by increasing the signal-to-noise ratio and allowing for mass spectrometry, which includes ionization using electron guns or lasers, and using various types of ion traps like FT-ICR, Penning, or quadrupole traps for separation and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional residual gas analyzer is used to detect contaminating substances, then the device structure remains simple, but the detection precision deteriorates because ions with extremely low partial pressures cannot be detected
Solution Approach 1:
The patent applies preliminary action by accumulating contaminating substance ions in a storage device (ion trap) before performing mass spectrometric analysis. This pre-accumulation step concentrates the ions that would otherwise be undetectable, enabling precise measurement of extremely low partial pressures while maintaining a relatively simple overall device structure
Solution Approach 2:
The storage device acts as an intermediary between the residual gas atmosphere and the mass spectrometer. It temporarily holds and concentrates the contaminating substance ions, allowing the mass spectrometer to analyze them with high precision without requiring continuous high-speed detection of trace ions in the gas phase
2Measurement precision
If the residual gas pressure is high, then the vacuum generating unit operates continuously, but the detection of contaminating substances deteriorates due to reduced signal-to-noise ratio
Solution Approach 1:
The patent extracts the contaminating substance ions from the complex residual gas atmosphere by using mass-selective ion trapping. The storage device selectively holds ions with specific mass-to-charge ratios corresponding to contaminating substances, separating them from the background gas ions and achieving high signal-to-noise ratio even at high residual gas pressures
Solution Approach 2:
The patent changes the operational parameters of the residual gas analyzer by implementing a storage mode where ions are accumulated over time before analysis. This temporal parameter change allows trace contaminating substances to be detected against the background of high residual gas pressure by concentrating the signal over multiple accumulation cycles
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
Enables the detection of extremely low concentrations of contaminating substances even at high residual gas pressures, improving the accuracy and reliability of contaminating substance detection, allowing for timely initiation of countermeasures to maintain mirror reflectivity and extend the operational lifetime of EUV lithography apparatuses.
Implementation Method 1
a residual gas analyzer having an ionization device for ionizing the contaminating substance
Implementation Method 2
ionization device for ionizing the contaminating substance, in particular an electron gun or a laser
Implementation Method 3
the provision of the storage device makes it possible to increase the detection sensitivity of the residual gas analyzer since the contaminating substance is available for measurement for a longer time
Implementation Method 4
use a quadrupole mass spectrometer to record a mass spectrum of the residual gas
Data Source
AI summary
An EUV (extreme ultraviolet) lithography apparatus (1) including: a housing (1a) enclosing an interior (15), at least one reflective optical element (5, 6, 8, 9, 10, 14.1 to 14.6) arranged in the interior (15), a vacuum generating unit (1b) generating a residual gas atmosphere in the interior (15), and a residual gas analyzer (18a, 18b) detecting at least one contaminating substance (17a) in the residual gas atmosphere. The residual gas analyzer (18a) has a storage device (21) having an ion trap for storing the contaminating substance (17a). Additionally, a method for detecting at least one contaminating substance by residual gas analysis of a residual gas atmosphere of an EUV lithography apparatus (1) having a housing (1a) having an interior (15), in which at least one reflective optical element (5, 6, 8, 9, 10, 14.1 to 14.6), is arranged, wherein the contaminating substance (17a) is stored in a storage device (21) in order to carry out the residual gas analysis.