edfas.org 13 ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 27 NO. 1 (continued on page 16) be explained by the recombination or the evolution to a stable state of unstable defects like Frenkel pairs, which could be generated during the channel implantation. The traps related to hydrogen may be present due to hydrogen incorporated during the selective epitaxial growth (SEG) of the raised source/drains from the SiH4 precursors used in chemical vapor deposition. The traps related to phosphor may also be associated with the HDD implantation. It may be noticed there are a number of traps that are frequently found in all technologies investigated, as T1 and T4, which are observed in all UTBOX, FinFET and GAA devices. Some traps are active only in UTBOX devices, as T5 and T6. The trap nature cannot be confirmed only for T8. Other systematic studies of the low frequency noise versus temperature effectuated in 32 nm n-channel tri-gate FinFET technologies underline that the additional process steps employed to boost the devices, as uniaxial and/or biaxial global strain to increase the device mobility and selective epitaxial growth of SiGe in the source and drain regions to reduce the device access resistance may lead to an increase of the number of the unknown trap, namely traps for which the nature cannot be confirmed.[13] However, for the investigated sub 16 nm technology nodes only for one trap (T8) the trap nature cannot be confirmed and the number of the detected traps seems to decrease for more advanced technologies. This may suggest that the passage from more nanoscaled device dimensions was accompanied by a maturity of the technological processes. IDENTIFIED TRAPS IN PASSIVE DEVICES Low frequency noise measurements were performed in heavily in-situ phosphorus doped polycrystalline silicon (polysilicon) serpentine resistance before and after irradiation. The samples were irradiated in the mono-energetic proton facility (KVI-CART). A monoenergetic beam of protons at 184 MeV with a flux of 8x107 p/cm².s was used.[22] A typical example of low frequency noise spectra is illustrated in Fig. 7a. It may be observed that the pristine sample exhibits only flicker and white noise contribution, (b) Fig. 7 (a) Only flicker and white noise are necessary to obtain the best agreement between experiment and model of (2) for the pristine sample (solid gray line). Three additional GR contributions are necessary to fit the irradiated sample (solid gray line). The 1/f tendency is represented by the short-dot line. T=300 K at fixed current of 60 µA. (b) GR noise evolution with the temperature for the irradiated sample at a fixed current of 60 µA. (a) while the irradiation clearly induces additional GR noise contribution. The evolution of the low frequency noise at fixed polarization with the temperature is plotted in Fig. 7b. Low frequency noise spectroscopy was performed in a temperature range of 300 to 330 K. Defects related to divacancies V2(-/--) (∆E of 0.42 eV) and V2(0/-) (∆E of 0.23 eV) and related to phosphorus-vacancy complex (V-P). The presence of divacancies (V2(-/--) and V2(0/-)) may be explained by recombination or evolution to a stable state of the unstable defects like Frenkel pairs, which could be generated during the irradiation, while the activation of the phosphorus vacancy complex (V-P) after irradiation process may be related to the fact that the samples are highly doped with phosphorus.
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