The effects of oxide thickness on the interface and oxide properties of metal-tantalum pentoxide-Si (MOS) capacitors

High dielectric constant tantalum-pentoxide insulating layers were prepared on p-type (100) crystalline silicon wafers using an RF magnetron sputtering technique. Then, metal-oxide-semiconductor (Al-Ta 2O 5-Si) structures were formed with various oxide thickness from 15 to 25 nm. Devices were characterized using the high frequency capacitance-voltage (C-V) spectroscopy method. From the analysis of the high frequency C-V curves, non-ideal effects such as oxide charges and interface trap densities have been evaluated. The results for Ta 2O 5 layers have been compared with those for conventional SiO 2 layers. Interface trap densities were found to be 1.6 ± 0.4×10 12 eV -1 cm -2 for Ta 2O 5 and about 2×10 11 eV -1 cm -2 for SiO 2 insulating layers. There was no clear thickness dependence of the interface trap densities for the Ta 2O 5 insulating layers

Capacitance-voltage spectroscopy in metal-tantalum pentoxide (Ta-O)-silicon mos capacitors

Thesis (Master)--Izmir Institute of Technology, Izmir, Physics, 2005Includes bibliographical references (leaves: 92-97)Text in English; Abstract:Turkish and Englishxiii, 97 leavesThe electronic properties of Al-Ta2O5-Si MOS capacitors with oxide layers prepared by RF magnetron sputtering with or without a prior nitridation process in N2O or NH3 gas environments at temperature ranges between 700 °C to 850 °C were investigated using Capacitance-Voltage (C-V) Spectroscopy to determine the quality of oxide layer and oxide-silicon interface. The theoretical ideal capacitance-voltage calculations were compared with the experimental capacitance-voltage results in order to evaluate effective oxide charges, Qeff , present inside Ta2O5 insulating layer and density of interface trap states, Dit, present at the Ta2O5-Si interface. In addition,dielectric constant, doping concentration, flat band voltage values were determined by using the experimental data. Finally, the effects of deposition conditions on Ta2O5 MOS capacitors were compared by using a reference sample of a MOS capacitor with native oxide SiO2. It has been found that dielectric constant value up to 12 have been reached for Ta2O5 insulating layers which increases the capacitance value several times than that of MOS capacitor with native oxide SiO2. The density of interface trap states, Dit, for unnitrided Ta2O5 MOS capacitors, values around 1.6x1012 cm-2 eV-1 have been detected which is much higher than that of MOS capacitor with native oxide SiO2. However, prior nitridation process enhances the interface properties and Dit values down to 2-5x1011 cm-2 eV-1 have been reached for the nitrided samples which is in the limits for MOS capacitors with high quality insulating layers. In addition, the effective oxide charges, Qeff, for unnitrided samples, values as high as 3x1012 cm-2 were detected. Even though nitridation process enhances interface properties, the effective oxide charges are found to be higher for nitrided samples. Best electrical and interface properties are obtained by nitridation process at 800 °C in N2O and NH3. It can be inferred that samples nitrided in N2O gas at 800 °C improves the dielectric constant above the level of SiO2 and decreases both Qeff and Dit levels to that of native oxide SiO2. These results show that a prior nitridation of p-silicon surface is a promising approach to improve both oxide and interface properties of Al-Ta2O5-Si MOS devices. However, further investigation is necessary to understand the nature of these oxide charges and interface properties of MOS devices with high dielectric constant oxide layers before integration into large scale fabrication

CAPACITANCE-VOLTAGE SPECTROSCOPY IN METAL – TANTALUM PENTOXIDE (Ta2O5) – SILICON MOS CAPACITORS

I would like to thank to my advisor, Assoc. Prof. Mehmet GÜNEŞ for his hel

The effects of oxide thickness on the interface and oxide properties of metal-tantalum pentoxide-Si (MOS) capacitors

High dielectric constant tantalum-pentoxide insulating layers were prepared on p-type (100) crystalline silicon wafers using an RF magnetron sputtering technique. Then, metal-oxide-semiconductor (Al-Ta 2O 5-Si) structures were formed with various oxide thickness from 15 to 25 nm. Devices were characterized using the high frequency capacitance-voltage (C-V) spectroscopy method. From the analysis of the high frequency C-V curves, non-ideal effects such as oxide charges and interface trap densities have been evaluated. The results for Ta 2O 5 layers have been compared with those for conventional SiO 2 layers. Interface trap densities were found to be 1.6 ± 0.4×10 12 eV -1 cm -2 for Ta 2O 5 and about 2×10 11 eV -1 cm -2 for SiO 2 insulating layers. There was no clear thickness dependence of the interface trap densities for the Ta 2O 5 insulating layers

Genetic Survey of Autosomal Recessive Peripheral Neuropathy Cases Unravels High Genetic Heterogeneity in a Turkish Cohort.

Background and Objectives Inherited peripheral neuropathies (IPNs) are a group of genetic disorders of the peripheral nervous system in which neuropathy is the only or the most predominant clinical feature. The most common type of IPN is Charcot-Marie-Tooth (CMT) disease. Autosomal recessive CMT (ARCMT) is generally more severe than dominant CMT and its genetic basis is poorly understood due to high clinical and genetic diversity. Here, we report clinical and genetic findings from 56 consanguineous Turkish families initially diagnosed with CMT disease

COVID-19 vaccination-related headache showed two different clusters in the long-term course: a prospective multicenter follow-up study (COVA-Head Study)

Abstract Background Although acute headache following COVID-19 vaccination is widely acknowledged, the long-term progression of these headaches remains poorly understood. Our objective was to identify various phenotypes of prolonged or worsened headaches associated with COVID-19 vaccination and document any changes in these phenotypes over an extended period. Additionally, we aimed to document the diverse headache presentations among patients with pre-existing primary headaches. Methods A multinational, prospective observational study was conducted to investigate prolonged or worsened headaches associated with COVID-19 vaccination. Questionnaires assessing COVID-19 vaccination-related headaches at three time points (initial visit, 3rd month follow-up, and 6th month follow-up) were developed for the study. Headache specialists/clinicians evaluated patients using these questionnaires in a prospective manner. Repeated K-means cluster analysis was performed to identify patient profiles with prolonged or worsened headaches related to COVID-19 vaccination. Results Among the 174 patients included in the study, there was a female-to-male ratio of 128 (73.6%) to 46 (26.4%). The mean age of the patient group was 45.2 ± 13.3 years, and 107 patients (61.5%) had a pre-existing history of primary headaches. Through the analysis, two major clusters were identified based on headache characteristics at each visit. During the first visit (n = 174), Cluster 1 primarily comprised patients with a history of primary headaches, frontal localization of pain, throbbing pain type, more severe headaches accompanied by symptoms such as nausea, phonophobia, photophobia, and osmophobia, and worsened by physical activity. In contrast, Cluster 2 consisted of patients with longer headache durations (over one month) and a stabbing/pressing quality of pain. Patients in Cluster 1 had a higher prevalence of migraine as the pre-existing primary headache disorder compared to Cluster 2 (90.48% vs. 68.18%, respectively; p = 0.005). Conclusion The identification of two distinct phenotypes of prolonged or worsened headaches related to COVID-19 vaccination can provide valuable clinical insights. Having an awareness of the potential worsening of headaches following COVID-19 vaccination, particularly in patients with a primary headache disorder such as migraine, can help clinicians and headache experts anticipate and adjust their treatment strategies accordingly. This knowledge can aid in preplanning treatment modifications and optimize patient care