Measurement of phosphorus segregation in silicon at the atomic scale using scanning tunneling microscopy

• Published in: Applied physics letters Vol. 85; no. 8; pp. 1359 - 1361
• Main Authors: Oberbeck, L., Curson, N. J., Hallam, T., Simmons, M. Y., Bilger, G., Clark, R. G.
• Format: Journal Article
• Language: English
• Published: United States American Institute of Physics 23-08-2004
• Subjects: ATOMS; DOPED MATERIALS; ENCAPSULATION; ION MICROPROBE ANALYSIS; MASS SPECTROSCOPY; MATERIALS SCIENCE; MOLECULAR BEAM EPITAXY; PHOSPHORUS; SCANNING TUNNELING MICROSCOPY; SEGREGATION; SEMICONDUCTOR MATERIALS; SILICON; SURFACES; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1784881

In order to fabricate precise atomic-scale devices in silicon using a combination of scanning tunneling microscopy (STM) to position dopant atoms and molecular beam epitaxy to encapsulate the dopants it is necessary to minimize the segregation∕diffusion of dopant atoms during silicon encapsulation. We characterize the surface segregation∕diffusion of phosphorus atoms from a
δ
-doped layer in silicon after encapsulation at
250
°
C
and room temperature using secondary ion mass spectrometry (SIMS) and STM. We show that the surface phosphorus density can be reduced to a few percent of the initial
δ
-doped density if the phosphorus atoms are encapsulated with 5 monolayers of epitaxial silicon at room temperature. We highlight the limitations of SIMS to determine phosphorus segregation at the atomic scale and the advantage of using STM directly.