Electrical Characteristics of the Uniaxial-Strained nMOSFET with a Fluorinated HfO2/SiON Gate Stack

Abstract

The channel fluorine implantation (CFI) process was integrated with the Si3N4 contact etch stop layer (SiN CESL) uniaxial-strained n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) with the hafnium oxide/silicon oxynitride (HfO2/SiON) gate stack. The SiN CESL process clearly improves basic electrical performance, due to induced uniaxial tensile strain within the channel. However, further integrating of the CFI process with the SiN CESL-strained nMOSFET exhibits nearly identical transconductance, subthreshold swing, drain current, gate leakage and breakdown voltage, which indicates that the strain effect is not affected by the fluorine incorporation. Moreover, hydrogen will diffuse toward the interface during the SiN deposition, then passivate dangling bonds to form weak Si-H bonds, which is detrimental for channel hot electron stress (CHES). Before hydrogen diffusion, fluorine can be used to terminate oxygen vacancies and dangling bonds, which can create stronger Hf-F and Si-F bonds to resist consequent stress. Accordingly, the reliability of constant voltage stress (CVS) and CHES for the SiN CESL uniaxial-strained nMOSFET can be further improved by the fluorinated HfO2/SiON using the CFI process. Nevertheless, the nMOSFET with either the SiN CESL or CFI process exhibits less charge detrapping, which means that a greater part of stress-induced charges would remain in the gate stack after nitrogen (SiN CESL) or fluorine (CFI) incorporation.

Synergic Impacts of CF4 Plasma Treatment and Post-thermal Annealing on the Nonvolatile Memory Performance of Charge-Trap-Assisted Memory Thin-Film Transistors Using Al–HfO2 Charge Trap and In–Ga–Zn–O Active Channel Layers

“…Alternatively, it was noteworthy that the largest MW value was obtained (12.0 V) for the A4 device. The synergic effects of CF 4 plasma and thermal annealing processes can be explained by following two feasible scenarios: (1) in terms of the Al:HfO 2 CTL bulk, two types of trap centers including the shallow trap sites located along the grain boundaries formed by crystallization and the deep trap sites within the midgap regions by incorporation of F ions could be generated by combined CTL engineering processes. − In other words, residual F ions at the Al:HfO 2 CTL surfaces could be diffused into the Al:HfO 2 bulks by postannealing treatment, inducing the deep trap sites due to the reactions with Hf dangling bonds. As a result, the charge-trapping efficiency could be quite improved by a significant increase in stable charge-trap sites; (2) in terms of the TL/CTL interfaces, the number of residual impurities and oxygen vacancies could be effectively reduced by combination of CF 4 plasma and annealing treatments, contributing to effective suppression of unstable charge-trapping events at interfaces.…”

“…On the other hand, it could be verified that the CTM-TFT using the Al:HfO 2 CTL treated with P+T exhibited far superior NVM characteristics and operational reliabilities among the fabricated devices, which correspond to indirect evidence for the F diffusion during the thermal annealing process at 500 °C. Additionally, it was also reported that F ions diffuse into the HfO 2 bulks during the CF 4 plasma and postannealing treatments, generating deep trap sites within the HfO 2 bandgap. − Therefore, from these viewpoints, it was reasonably suggested that the stable charge-trap sites can be generated by F incorporation into the bulk region of the Al:HfO 2 CTL. Alternatively, small degrees of modulations in numerical values of the bandgap with CTL engineering processes were supposed to have negligible effects on the NVM operations of the CTM-TFTs.…”

“…Thus, it is necessary to stably generate the trap sites to effectively enhance the charge-trap/detrap events that originated from Fowler–Nordheim (F–N) tunneling via defect sites located in the bandgap. , Recent publications propose the feasible generation of deep trap sites within the HfO 2 thin film by means of incorporation of fluorine (F) ions during the CF 4 plasma treatment and a high-temperature postannealing process. − These sophisticatedly generated deep trap sites can be suggested to work as stable charge-trap sites within the doped HfO 2 CTLs, resulting in the enhancement of P/E operation efficiency. Furthermore, the CF 4 plasma treatment can also be expected to improve the thin-film qualities in terms of interfacial chemical bonding states, dielectric breakdown field, and leakage current.…”

Electrical Properties and Interfacial Studies of HfxTi1–xO2 High Permittivity Gate Insulators Deposited on Germanium Substrates

“…Titanium doping was found to suppress the oxygen vacancies in tantalum oxide capacitors, which resulted in a significant reduction in the leakage current [38]. For the HfO 2 capacitors, there are also a considerable number of oxygen vacancies [39,40,41,42], which could potentially be suppressed when titanium is doped in the HfO 2 .…”

Passivation of oxygen vacancy defects in conductive ZnO nanoparticles via low-temperature annealing in NF3

“…In recent decades, much effort has been devoted to exploring passivation methods for V O defects. The primary strategy is to use various anions such as nitrogen, oxygen and fluorine to coordinate with metal dangling bonds in MOSs [11]. The passivation process is conducted under high temperature or with the aid of plasma.…”