Out-diffusion and precipitation of copper in silicon: An electrostatic model
1Department of Materials Science, University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Physical Review Letters
|December 2, 2000
Summary
Copper behavior in silicon depends on initial concentration. Below critical levels, copper moves to the surface; above, it precipitates within the bulk material due to electrostatic interactions.
Area of Science:
- Materials Science
- Semiconductor Physics
- Solid-State Chemistry
Background:
- Understanding copper behavior in silicon is crucial for semiconductor device fabrication and reliability.
- Interstitial and precipitated copper species significantly impact silicon's electrical properties.
Purpose of the Study:
- To investigate the partitioning of copper between interstitial and precipitated phases in silicon.
- To determine the critical copper concentration influencing its distribution.
- To elucidate the mechanisms governing copper diffusion and precipitation in silicon.
Main Methods:
- Intentional high-temperature copper contamination of silicon.
- Rapid quenching to room temperature to freeze-in concentrations.
- Analysis of mobile interstitial and precipitated copper species.
Main Results:
- Copper predominantly diffuses to the surface below a critical contamination level.
- For higher initial concentrations, copper mainly precipitates within the silicon bulk.
- The critical contamination threshold is defined as the acceptor concentration plus 10^16 cm^-3.
- Electrostatic interactions between interstitial copper and precipitates explain this behavior.
Conclusions:
- Copper distribution in silicon is concentration-dependent, transitioning from surface diffusion to bulk precipitation.
- Electrostatic forces play a key role in governing copper's phase partitioning in silicon.
- The findings provide insights into controlling metallic impurities in semiconductor materials.
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