Hydrogen is released from hydrogenated silicon nitride (SiNx:H) during thermal treatments. The formation of molecular hydrogen (H2) in SiNx:H layers with low mass density is confirmed by Raman spectroscopy. However, no H2 is observed in layers with a high mass density despite clear evidence that hydrogen diffuses through those layers. Therefore hydrogen migrates in those layers in a different form. This is consistent with the observed improvement of the hydrogen passivation of silicon substrates using thermally treated high density SiNx:H antireflection coatings.

We present a detailed investigation on the origin of the room-temperature visible luminescence in hydrogenated amorphous silicon nitride films. In combination with Raman spectroscopy and high resolution transmission electron microscopy, we demonstrate clearly that the red light emission originates from amorphous silicon quantum dots. On the basis of the redshift of peak position, narrowing of bandwidth, and temperature quenching of luminescence, we attribute the green emission to the bandtail recombination of carriers. In addition, the blue luminescence is assigned to the silicon-related defects according to the analysis for the gap states in silicon nitride.

Articles you may be interested inDetermining factor of effective work function in metal/bi-layer high-k gate stack structure studied by photoemission spectroscopy Appl. Phys. Lett. 100, 112906 (2012); 10.1063/1.3695166 Photoinduced charge-trapping phenomena in metal/high-k gate stack structures studied by synchrotron radiation photoemission spectroscopy Appl. Phys. Lett. 96, 162902 (2010); 10.1063/1.3409162 Thermally stable high effective work function TaCN thin films for metal gate electrode applications Titanium nitride (TiN) films have been used as gate electrode on metal-oxide-semiconductor (MOS) devices. TiN effective work function (EWF) values have been often reported as suitable for pMOS. For nMOS devices, a gate electrode with sufficient low EWF value with a similar robustness as TiN is a challenge. Thus, in this work, aluminum (Al) is incorporated into the TiN layer to reduce the EWF values, which allows the use of this electrode in nMOS devices. Titanium aluminum (TiAl), Al, and aluminum nitride (AlN) layers were introduced between the high-k (HfO 2 ) dielectric and TiN electrode as Al diffusion sources. Pt/TiN (with Al diffusion) and Pt/TiN/TiAl/TiN structures were obtained and TiN EWF values were reduced of 0.37 eV and 1.09 eV, respectively. The study of TiN/AlN/HfO 2 /SiO 2 /Si/Al structures demonstrated that AlN layer can be used as an alternative film for TiN EWF tuning. A decrease of 0.26 eV and 0.45 eV on TiN EWF values were extracted from AlN/TiN stack and AlN/TiN laminate stack, respectively. AlN/TiN laminate structures have been shown to be more effective to reduce the TiN work function than just increasing the AlN thickness. V C 2014 AIP Publishing LLC.

We report on the optical properties and local bonding configurations of both as-deposited and postannealed hydrogenated amorphous silicon nitride ͑a-SiN x :H͒ thin films grown on crystalline Si substrates with x approximately 1.2± 0.1. Ultraviolet optical reflection and infrared ͑IR͒ absorption measurements were applied to characterize the films. A method simply based on optical reflection spectra is proposed for accurate determination of the optical band gap, band tail, wavelength-dependent refractive index and extinction coefficient, as well as the film thickness, suggesting that the Tauc-Lorentz ͓G. E. Jellison, Jr. and F. A. Modine, Appl. Phys. Lett. 69, 371 ͑1996͒; 69, 2137 ͑1996͔͒ model with the inclusion of Urbach tail is the optimal one to describe the optical response of a-SiN x : H films. The yielded optical parameters can be related well to the film microstructure as revealed by the IR absorption analysis. These results have implications for future deposition controlling and device applications.

Hydrogenation by high temperature rapid annealing of SiNx:H is found to be very effective on the defects responsible for the carrier trapping effect in multicrystalline silicon. The passivation effect is reversible and is annihilated by a long thermal annealing. As for the passivation of deep, lifetime killing defects, the efficiency of “trap” removal by the short thermal treatment depends on the density of the SiNx:H layer. This effect is, in fact, well correlated with performance improvement observed in solar cells. The parallelism between the trap and recombination center passivation effects suggests that they originate from the same defect.