Electron Energy Sweep Mass Spectrometry for Plasma Species Quantification
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Solution Overview
Problem
Conventional mass spectrometers used in semiconductor and plasma processes are expensive, have a large footprint, limited measurement range, and require complex data analysis, leading to inaccurate and incomplete quantification of species in processing chambers.
Innovation Solution
A plasma processing system with a mass spectrometer that includes a shutter and an ionizer capable of sweeping electron energy through multiple steps, allowing for accurate quantification of species by distinguishing between different energy levels and sources, and automatically compensating for background effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mass spectrometer is used to quantify species in a processing chamber, then measurement accuracy is improved, but device cost and footprint increase
Solution Approach 1:
The system segments the measurement process into distinct energy steps, with the ionizer operating at multiple discrete electron energies (e.g., 5-100 eV) to differentiate species. This segmentation allows accurate species identification without requiring a large, complex mass spectrometer, thereby reducing device footprint while maintaining measurement precision.
Solution Approach 2:
The ionizer's electron energy parameter is swept through a range of values to change the ionization characteristics. By varying electron energy, the system can selectively ionize different species based on their ionization potentials, enabling accurate quantification with a compact device rather than a large conventional mass spectrometer.
2Measurement precision
If conventional mass spectrometry is used for species quantification, then measurement capability is improved, but data collection speed decreases
Solution Approach 1:
The electron energy is swept periodically through discrete steps, with each step holding for a defined duration to collect ion current data. This periodic sampling approach enables rapid data collection across the energy range, improving productivity while maintaining species identification capability through the systematic energy variation.
3Measurement precision
If electron energy sweeping is performed to distinguish species, then measurement precision is improved, but measurement complexity increases
Solution Approach 1:
The system uses the natural ionization characteristics of different species at various electron energies to self-differentiate them. By sweeping electron energy and measuring ion currents, the system automatically identifies species based on their unique ionization thresholds and patterns, reducing the need for complex external analysis equipment or expert intervention.
Solution Approach 2:
The system incorporates feedback mechanisms where ion current measurements at each energy step inform the next measurement decisions. The controller adjusts electron energy based on detected species signatures, enabling automated species identification and quantification that simplifies the overall measurement process despite the energy sweeping requirement.
4Measurement precision
If background subtraction is performed to improve accuracy, then measurement precision is improved, but data collection time increases
Solution Approach 1:
Background measurements are taken at each electron energy step before introducing the sample or during baseline conditions. This preliminary background characterization allows for accurate subtraction from subsequent sample measurements, improving quantification precision without requiring excessive additional measurement time, as the background is captured efficiently during the energy sweep.
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 solution reduces costs and footprint, improves data collection speed, and enhances accuracy by distinguishing between species from different sources and detecting metastable species, while reducing the need for expert analysis.
Implementation Method 1
an ionizer configured to ionize species of the particle beam by sweeping through a range of electron energies in a plurality of energy steps
Implementation Method 2
The first orifice is configured to generate the particle beam from the plasma using a pressure differential between the shutter chamber and the plasma chamber
Data Source
AI summary
A plasma processing system includes a plasma chamber configured to contain a plasma, a shutter chamber fluidically coupled to the plasma chamber via a first orifice, a mass spectrometer fluidically coupled to the shutter chamber, and a shutter disposed in the shutter chamber between the first orifice and the mass spectrometer in the path of a particle beam. The first orifice is configured to generate the particle beam from the plasma using a pressure differential between the shutter chamber and the plasma chamber. The mass spectrometer includes an ionizer configured to ionize species of the particle beam by sweeping through a range of electron energies in a plurality of energy steps. The shutter is configured to open and close during each of the plurality of energy steps.