Dose-rate effects on the formation of ultra-shallow junctions with low-energy B+ and BF2+ ion implants
| Autor: | Sonu L. Daryanani, Carlton M. Osburn, James J Cummings, Scott W. Falk, Daniel F. Downey |
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| Rok vydání: | 1997 |
| Předmět: |
Materials science
Annealing (metallurgy) Metals and Alloys Analytical chemistry chemistry.chemical_element Surfaces and Interfaces Dopant Activation Surfaces Coatings and Films Electronic Optical and Magnetic Materials Ion Secondary ion mass spectrometry Ion implantation chemistry Materials Chemistry Fluorine Boron Sheet resistance |
| Zdroj: | Thin Solid Films. :562-569 |
| ISSN: | 0040-6090 |
| Popis: | 11B+ and 49BF2+ implants on a Varian VIISion-80 PLUS Ion Implanter from 2.0 to 8.9 keV at a dose of 1E15/cm2, and at various controlled and measured (in situ) peak beam-current densities, ranging from 3 to 600 μA/cm2, were investigated to study the effects of dose rate on the formation of ultra-shallow junctions. The implants and annealing conditions were chosen to produce junction depths, as measured by secondary ion mass spectrometry (SIMS), of 40 to 150 nm. In addition, a comprehensive study of B vs. BF2 at a boron effective energy of 2.0 keV (i.e. B at 2.0 keV and BF2 at 8.9 keV) was undertaken. The results show that for the implant conditions investigated the dose rate does not have a significant effect (if any) on the junction depth and that there is a distinct advantage to BF2 implants in forming shallower junctions. This advantage is not dose-rate related, but is related to the presence of fluorine. This paper also addresses the effects of pre-amorphization with Ge on dopant activation and on transient enhanced diffusion, and annealing techniques to optimize sheet resistance while minimizing junction depths. The background concentration of O2 during anneal was found to have a dramatic impact on the annealed junction (from oxidation-enhanced diffusion). Reducing the O2 concentration to trace amounts, produced the shallowest junctions observed. By combining those techniques which reduce boron diffusion, junctions that were only 39 nm deep, having a sheet resistance of 361 Ω/sq., were fabricated with 5 keV BF2. |
| Databáze: | OpenAIRE |
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