Investigation of degradation mechanism after negative bias temperature stress in Si/SiGe channel metal-oxide-semiconductor capacitors induced by hydrogen diffusion

In this research, based on I-V and C-V measurement at different temperatures, the interface defect density in the device with the Si/SiGe channel was discussed. In addition, negative bias temperature instability (NBTI) is also studied. In previous research, most of the flat-band voltage (VFB) shifts during NBTI stress was attributed to hole injection. In this article, however, the release of atomic hydrogen from the Si–H bonds at the SiOV2/Si interface and at the SiGe interface produces a fixed oxide charge, which causes VFB shifts which vary with material.

Effects of polyimide curing on image sticking behaviors of flexible displays

Flexible displays on a polyimide (PI) substrate are widely regarded as a promising next-generation display technology due to their versatility in various applications. Among other bendable materials used as display panel substrates, PI is especially suitable for flexible displays for its high glass transition temperature and low coefficient of thermal expansion. PI cured under various temperatures (260 °C, 360 °C, and 460 °C) was implemented in metal–insulator–metal (MIM) capacitors, amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFT), and actual display panels to analyze device stability and panel product characteristics. Through electrical analysis of the MIM capacitor, it was confirmed that the charging effect in the PI substrates intensified as the PI curing temperature increased. The threshold voltage shift (ΔVth) of the samples was found to increase with rising curing temperature under negative bias temperature stress (NBTS) due to the charging effect. Our analyses also show that increasing ΔVth exacerbates the image sticking phenomenon observed in display panels. These findings ultimately present a direct correlation between the curing temperature of polyimide substrates and the panel image sticking phenomenon, which could provide an insight into the improvement of future PI-substrate-based displays.

Threshold voltage instability and polyimide charging effects of LTPS TFTs for flexible displays

In this paper, we investigate the Vth shift of p-type LTPS TFTs fabricated on a polyimide (PI) and glass substrate considering charging phenomena. The Vth of the LTPS TFTs with a PI substrate positively shift after a bias temperature stress test. However, the Vth with a glass substrate rarely changed even with increasing stress. Such a positive Vth shift results from the negative charging of fluorine stemmed from the PI under the gate bias. In fact, the C–V characterization on the metal–insulator-metal capacitor reveals that charging at the SiO2/PI interface depends on the applied gate bias and the PI material, which agrees well with the TCAD simulation and SIMS analyses. As a result, the charging at the SiO2/PI interface contributes to the Vth shift of the LTPS TFTs leading to image sticking.

Influence of Si–In–Zn–O/Ag/Si–In–Zn–O Electrode on Amorphous Si–Zn–Sn–O Thin Film Transistors

Amorphous SiZnSnO (a-SZTO) thin film transistors (TFTs) have been reported with transparent Si–In–Zn–O/Ag/Si–In–Zn–O (SIZO OMO) source/drain (S/D) electrodes. The characteristics of ITO and SIZO OMO electrodes were compared with conventional metal electrode of Ti/Al. The SZTO TFT with SIZO OMO electrode showed high field effect mobility of 17.69 cm2/Vs, threshold voltage of 4.05 V and low sub-threshold swing of 0.33 V/decade. The stability of a-SZTO TFTs with SIZO OMO electrode was measured ∆VTH = 1.4 V at 333 K, and − 20 V for 7200 s under negative bias temperature stress (NBTS).

Defect Analysis and Reliability Characteristics of (HfZrO4)1−x(SiO2)x High-κ Dielectrics

Hafnium zirconium silicon oxide ((HfZrO4)1−x(SiO2)x) materials were investigated through the defect analysis and reliability characterization for next generation high-κ dielectric. Silicate doped hafnium zirconium oxide (HfZrO4) films showed a reduction of negative flat-band voltage (Vfb) shift compared to pure HfZrO4. This result was caused by a decrease in donor-like interface traps (Dit) and positive border traps (Nbt). As the silicon oxide (SiO2) content increased, the Vfb was shifted in the positive direction from −1.23 to −1.10 to −0.91 V and the slope of the capacitance–voltage (C–V) curve increased. The nonparallel shift of the C–V characteristics was affected by the Dit, while the Nbt was responsible for the parallel C–V curve shift. The values of Dit reduced from 4.3 × 1011, 3.5 × 1011, and 3.0 × 1011 cm−2eV−1, as well as the values of Nbt were decreased from 5.24, 3.90 to 2.26 × 1012 cm−2. Finally, reduction of defects in the HfZrO4-base film with an addition of SiO2 affected the gate oxide reliability characteristics, such as gate leakage current (JG), bias temperature stress instability (BTSI), and time dependent gate dielectric breakdown (TDDB).