Niobium Contamination in Silicon

Polignano, M. L.; Codegoni, Davide; Borionetti, G.; Bonoli, F.; Brivio, Jacopo; Greco, Stefano; Marino, Antigone; Monge, Paolo; Patoprsta, Ivana; Riva, C.

doi:10.1149/1.3485688

Cited by 8 publications

(6 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Subsequent work mainly by deeplevel transient spectroscopy (DLTS) showed that early TMs are electrically active and responsible for several deep levels in the gap (see for example Refs. [1,2,5,6] and references therein). It is, therefore, of primary interest to be able to determine accurately the signature of these TMs, in particular, the location of their electrical levels in the gap.…”

Section: Introductionmentioning

confidence: 99%

Electrical Levels and Diffusion Barriers of Early 3d and 4d Transition Metals in Silicon

Marinopoulos

Santos

Coutinho

2015

SSP

View full text Add to dashboard Cite

Early transition metals (TMs) of the 3d and 4d rows are undesired contaminants in solar- and electronic-grade Si. From the theoretical standpoint, understanding the properties of these TMs in silicon still remains a challenging problem owing to the strong correlations among the TM d-electrons. The present study proposes a first-principles Hubbard-corrected DFT+U approach, with on-site parameters accounting separately for electron Coulomb (U) and exchange (J) effects. We use this approach together with conventional DFT to determine electrical levels and migration barriers of early 3d (Ti, V and Cr) and 4d (Zr, Nb and Mo) TMs in Si. Comparisons with experimental data allowed us to uniquely assign the deep levels in the gap appraising also the effect of on-site correlation. Our results also resolve existing controversies in the literature concerning the type and origin of the donor levels of Cr and Mo. For all the metals, with the exception of Cr, high barriers of interstitial diffusion are obtained, thus confirming that most of these TMs are slow diffusers in silicon.

show abstract

Section: Introductionmentioning

confidence: 99%

Electrical Levels and Diffusion Barriers of Early 3d and 4d Transition Metals in Silicon

Marinopoulos

Santos

Coutinho

2015

SSP

View full text Add to dashboard Cite

show abstract

“…Metal surface segregation: the example of niobium. In a previous work [3] we showed that niobium is very prone to surface segregation. Evidence of surface segregation even after a RTA treatment was given by surface photovoltage, Elymat and DLTS, showing that with 10 12 cm -2 dose less than 10% of the dose was in the solid solution.…”

Section: Resultsmentioning

confidence: 84%

“…Low doses (10 11 cm -2 to 10 12 cm -2 ) were considered, in order to limit ourselves to realistic contamination levels in non-optimum process conditions. Niobium was implanted at the wafer front side, because in a previous study it was shown to be a slow diffuser [3], so it could not reach the opposite side of the wafer with a reasonable thermal treatment. The samples were oxidized to 1000 Å and implanted with 1 MeV energy.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of Contaminated Oxide-Silicon Interfaces

Polignano

Codegoni

Castellano

et al. 2011

SSP

Self Cite

View full text Add to dashboard Cite

Methods for the analysis of the oxide-silicon interface were compared for their ability to reveal metal segregation at the interface and organic contamination. The impact of these contaminations on surface recombination velocity measurements, on capacitance vs. voltage, conductance vs. voltage and capacitance vs. time measurements and on MOS-DLTS spectra was studied. Niobium-contaminated wafers were used as an example of metal surface segregation, because it was previously shown that niobium is prone to surface segregation. Interface state density measurements obtained by the conductance method showed a limited impact of niobium implantation. Vice versa significant effects were found in MOS-DLTS spectra. For what concerns organic contamination, MOS-DLTS showed the most significant effects from the point-of-view of the intrinsic properties of the silicon oxide - silicon interface, and GOI tests demonstrate a clear impact of the organic contamination on MOS capacitors oxide breakdown events.

show abstract

“…For these contaminants, a generation lifetime in the range 10 −3 -10 −2 s corresponds to a concentration of the order of 10 10 cm −3 . 20,21 In this work the capacitors were pulsed from flatband voltage conditions to ±5 V deep depletion conditions, and the steady state recovery was recorded by measuring the capacitance with 100 kHz frequency signal. To limit perimeter effects, square capacitors with 2.25 mm 2 area were used for these measurements.…”

Section: Experimental Techniques-surface Photovoltage (Spv)-mentioning

confidence: 99%

Molybdenum and Tungsten Contamination in MOS Capacitors

Polignano¹,

Galbiati²,

Grasso³

et al. 2016

ECS J. Solid State Sci. Technol.

View full text Add to dashboard Cite

In this paper, the impact of molybdenum and tungsten contamination on the properties of MOS capacitors is analyzed, with the aim to investigate whether measurements of MOS capacitors can be used to detect this sort of contaminants. Surface Photovoltage (SPV) measurements of carrier diffusion length and of the oxide charge (obtained from high injection SPV) are compared to the results of MOS capacitor measurements. In agreement with previous DLTS data, both SPV and generation lifetime data show that molybdenum remains in the solid solution in silicon in the studied dose range. As a consequence, molybdenum contamination has limited impact on the interface state density at the oxide-silicon interface. Vice versa, tungsten was shown to deactivate starting from rather low doses (1011 cm−2). Tungsten deactivation is associated with the formation of new peaks in interface state density spectra. However, no tungsten segregation at the oxide-silicon interface could be detected by ToF-SIMS measurements. We suggest that in MOS capacitors tungsten deactivation is associated with segregation in the oxide layer. SPV has limited sensitivity to these impurities. Generation lifetime is a good monitor of tungsten contamination, whereas for molybdenum DLTS is the most sensitive contamination monitor.

show abstract

Niobium Contamination in Silicon

Cited by 8 publications

References 23 publications

Electrical Levels and Diffusion Barriers of Early 3d and 4d Transition Metals in Silicon

Electrical Levels and Diffusion Barriers of Early 3d and 4d Transition Metals in Silicon

Analysis of Contaminated Oxide-Silicon Interfaces

Molybdenum and Tungsten Contamination in MOS Capacitors

Contact Info

Product

Resources

About