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Annealing Studies on Low Energy As+ and As2+ Implants

Published online by Cambridge University Press:  10 February 2011

Raghu Srinivasa
Affiliation:
ECE Department, University of Texas, Austin, TX-78758
Vikas Agarwal
Affiliation:
ECE Department, University of Texas, Austin, TX-78758
Jinning Liu
Affiliation:
Varian Ion Implant Systems, Gloucester, MA-01930
Daniel F. Downey
Affiliation:
Varian Ion Implant Systems, Gloucester, MA-01930
Sanjay Banerjee
Affiliation:
ECE Department, University of Texas, Austin, TX-78758
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Abstract

2 keV to 10 keV arsenic, As+, and arsenic dimer ions, As 2+, were implanted into silicon at a dose of le15 cm-2 and 3e 15 cm-2 at 0° and 7°' tilt angles. For bare wafers, a low concentration of oxygen is required to provide sufficient capping during anneal to minimize out-diffusion. In the presence of oxygen, enhanced diffusion occurs during the anneal, the extent of which is a function of the concentration of oxygen and the temperature of anneal. The oxidation enhanced diffusion (OED) is significant at anneal temperatures above 1050°C. The extent of OED is observed to be more significant for the samples with lower energy As+ implants. An alternative technique for minimizing OED, without much out-diffusion, is the use of higher energy, 5 keV implants through a screen oxide. For identical anneal conditions, 5 keV As+ implants through a 40 Å screen oxide offer junction depth and sheet resistance values equivalent to that of 2 keV implants into bare silicon. As the screen oxide is sufficient to cap the out-diffusion of dopants, a nitrogen ambient or a lower temperature could be employed to get shallower junctions without much degradation in the sheet resistance. Further reduction in junction depths can be achieved by using the As 2+ implants.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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References

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