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In this study, we investigated the influence of quasi-one-dimensional (Quasi-1D) characteristics on the source and drain contact resistances within vertical nanowire (NW) field-effect transistors (FETs) of diminutive diameter. The top contact of the NW is segregated into two distinct regions: the first encompassing the upper surface, designated as the axial contact, and the second encircling the side surface, known as the radial contact, which is formed during the top-contact metal deposition process. Quantum confinement effects, prominent within Quasi-1D NWs, exert significant constraints on radial transport, consequently inducing a noticeable impact on contact resistance. Notably, in the radial direction, electron tunneling occurs only through quantized, discrete energy levels. Conversely, along the axial direction, electron tunneling freely traverses continuous energy levels. In a meticulous numerical analysis, these disparities in transport mechanisms unveiled that NWs with diameters below 30 nm exhibit a markedly higher radial contact resistance compared to their axial counterparts. Furthermore, an increase in the overlap length (less than 5 nm) contributes to a modest reduction in radial resistance; however, it remains consistently higher than the axial contact resistance. [ABSTRACT FROM AUTHOR]

Effects of carbon implantation (C-imp) on the contact characteristics of Ti/Ge contact were investigated. The C-imp into Ti/Ge system was developed to reduce severe Fermi-level pinning (FLP) and to improve the thermal stability of Ti/Ge contact. The current density (J)-voltage (V) characteristics showed that the rectifying behavior of Ti/Ge contact into an Ohmic-like behavior with C-imp. The lowering of Schottky barrier height (SBH) indicated that the C-imp could mitigate FLP. In addition, it allows a lower specific contact resistivity (ρc) at the rapid thermal annealing (RTA) temperatures in a range of 450–600 °C. A secondary ion mass spectrometry (SIMS) showed that C-imp facilitates the dopant segregation at the interface. In addition, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) mapping showed that after RTA at 600 °C, C-imp enhances the diffusion of Ge atoms into Ti layer at the interface of Ti/Ge. Thus, carbon implantation into Ge substrate can effectively reduce FLP and improve contact characteristics. [ABSTRACT FROM AUTHOR]

We present the fabrication and electrical characteristics of nanonet-channel (NET) low-temperature polysilicon channel (LTPS) thin-film transistors (TFTs) using a nanosphere-assisted patterning (NAP) technique. The NAP technique is introduced to form a nanonet-channel instead of the electron beam lithography (EBL) or conventional photolithography method. The size and space of the holes in the nanonet structure are well controlled by oxygen plasma treatment and a metal lift-off process. The nanonet-channel TFTs show improved electrical characteristics in terms of the ION/IOFF, threshold voltage, and subthreshold swing compared with conventional planar devices. The nanonet-channel devices also show a high immunity to hot-carrier injection and a lower variation of electrical characteristics. The standard deviation of VTH (σVTH) is reduced by 33% for a nanonet-channel device with a gate length of 3 μm, which is mainly attributed to the reduction of the grain boundary traps and enhanced gate controllability. These results suggest that the cost-effective NAP technique is promising for manufacturing high-performance nanonet-channel LTPS TFTs with lower electrical variations. [ABSTRACT FROM AUTHOR]

• Carbon pre-implantation improves the thermal stability of NiSi. • Carbon clusters are formed the vicinity of NiSi/Si interface. • NiSi agglomeration suppressed by carbon clusters formed at the NiSi/Si interface. • Ni diffusion is inhibited by carbon clusters at the interface of NiSi/Si. • The effect of carbon pre-implantation could be analyzed using atom probe at near-atomic scale. We have investigated effects of carbon pre-implantation (C-implantation) on electrical and morphological properties of nickel silicide (NiSi). C-implanted NiSi showed an improved thermal stability on the electrical characteristics in terms of sheet resistance (R sh) and contact resistivity (ρ c) after rapid thermal annealing (RTA) up to 700 °C. The process temperature window was extended by ~100 °C when the C-implantation with a dose of 1 × 1015 cm−2 was introduced. From transmission electron microscopy (TEM) images, the suppression of NiSi agglomeration was confirmed in the C-implanted NiSi. In order to further understand the role of carbon, atom probe tomography (APT) was performed. The three-dimensional (3D) distribution and composition of elements by APT unveiled the formation of carbon clusters with a diameter ranging from 2 to 10 nm near the NiSi/Si interface. The carbon clusters with a peak concentration of 6.0 at. % at the NiSi/Si interface can effectively suppress NiSi agglomeration and Ni diffusion, resulting in improving thermal stability of the NiSi. [ABSTRACT FROM AUTHOR]