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Atomistic mechanism of boron diffusion in silicon
Davide De Salvador1, Enrico Napolitani, Salvatore Mirabella
1MATIS INFM-CNR and Padova University, Physics Department, via Marzolo 8, 35131 Padova, Italy. desalvador@padova.infm.it
Physical Review Letters
|February 7, 2007
Summary
Boron (B) diffusion in silicon (Si) depends on free hole concentration. Boron interacts with silicon self-interstitials (I) forming mobile BI complexes, with diffusion influenced by hole levels.
Area of Science:
- Materials Science
- Semiconductor Physics
- Solid-State Chemistry
Background:
- Boron (B) diffusion in crystalline silicon (Si) is crucial for semiconductor device fabrication.
- Understanding the diffusion mechanisms, particularly the role of silicon self-interstitials (I), is essential for process control.
- The influence of free hole concentration on B diffusion kinetics requires detailed investigation.
Purpose of the Study:
- To experimentally investigate the dependence of Boron-Silicon self-interstitial (BI) complex formation and migration on free hole concentration (p) in crystalline Si.
- To elucidate the mechanisms of BI complex formation and diffusion in different free hole concentration regimes.
- To determine how the charge state of self-interstitials and the BI complex affects diffusion.
Main Methods:
- Experimental study of Boron diffusion in crystalline silicon.
- Analysis of the frequency (g) of BI complex formation and the average migration length (lambda) of the BI complex.
- Correlation of diffusion parameters (g and lambda) with varying free hole concentrations (p).
Main Results:
- Both BI complex formation frequency (g) and migration length (lambda) are strongly dependent on free hole concentration (p).
- At low p, g is constant and lambda increases with p, indicating interaction with neutral self-interstitials.
- At high p, g increases superlinearly and lambda decreases with p, suggesting interaction with double positive self-interstitials and charge state changes.
Conclusions:
- Boron diffusion in silicon occurs via the formation of mobile BI complexes.
- The diffusion mechanism transitions between two regimes based on free hole concentration, involving interactions with neutral and positively charged self-interstitials.
- The charge state of the BI complex is modulated by free holes, influencing its diffusion behavior.
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