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Atom counting at surfaces
Science (New York, N.Y.)
|January 6, 1989
Summary
Multiphoton resonance ionization coupled with ion bombardment achieves ultra-sensitive surface analysis. This technique detects indium dopants on silicon at 9 parts per trillion, a 100x improvement over prior methods.
Area of Science:
- Materials Science
- Surface Analysis
- Analytical Chemistry
Background:
- Accurate dopant concentration measurement is crucial for semiconductor performance.
- Existing surface analysis techniques have limitations in sensitivity and resolution.
- Indium (In) is a key dopant in silicon (Si) based materials.
Purpose of the Study:
- To develop a highly sensitive method for quantifying indium dopant concentrations on silicon surfaces.
- To establish a new benchmark for surface analysis detection limits.
Main Methods:
- Combined multiphoton resonance ionization with energetic ion bombardment.
- Optimized experimental configuration for sampling and detection efficiency.
- Minimized background noise for enhanced signal-to-noise ratio.
Main Results:
- Achieved a linear correlation between surface indium concentration and bulk values.
- Established a detection limit of 9 parts per trillion for indium on silicon.
- Demonstrated a mass resolution exceeding 160.
- Enabled counting of as few as 180 surface atoms.
Conclusions:
- The combined technique offers unprecedented sensitivity for surface dopant analysis.
- This method significantly surpasses previous surface analysis capabilities by a factor of 100.
- The optimized approach provides a powerful tool for materials characterization and quality control.
