In this study, the effects of the Ti layer on resistive switching behaviors of HfO x -based resistive switching random access memory (ReRAM) were investigated. After introducing a thin Ti layer (>10 nm) between the Ta and HfO x layers, both cycle-to-cycle uniformity within one cell and cell-to-cell uniformity were significantly improved. In addition, the higher ON/OFF ratio was obtained owing to the resistance increase in the high-resistance state, and a high device yield (>90%) also was achieved. The improvement of switching uniformity can be explained by the Ti doping effect, which is caused by the diffusion of Ti into the HfO x layer. In addition, the Ti layer had the effect of generating more oxygen vacancies in the HfO x layer, which led to the lowering of forming voltage (>2.6 V). To confirm the change in the amount of oxygen vacancies, X-ray photoelectron spectroscopy analysis was performed. The formation of the TiO x layer and the Ti doping effect are considered to contribute to the generation of more oxygen vacancies in the HfO x layer.
EUV mask absorber sidewall angle should be measured for mask Optical Proximity Correction and shadow effect estimation. Hence, verifying the three-dimensional profile of mask topography has become a challenge in EUV mask inspection. This paper evaluates EUV mask sidewall angle measurement by Field-Emission Critical Dimension (CD)-Scanning Electron Microscope (SEM) using JEOL JSM-7401F. SEM only produces two-dimensional gray images. Forming three-dimensional profiles from these images is a critical requirement for the sidewall angle measurement. To obtain three-dimensional information, absorber edge width has to be measured first to measure sidewall angle. We can calculate absorber sidewall angle with the exactly measured edge width and absorber height. Edge width narrows with steeper sidewall angle. We used the image processing function of Matlab to obtain absorber edge width accurately. In the end, every measured sidewall angle was compared to Transmission Electron Microscope (TEM) images to evaluate the validity of SEM results. Measured sidewall angles by SEM and TEM cross-section images have average tolerances of 0.62 degrees.
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