Papers by Keyword: Oxide Breakdown

Abstract: The gate oxide reliability and channel mobility of carbon face (000-1) 4H Silicon Carbide (SiC) MOSFETs are investigated. Several gate oxidation processes including dry oxygen, pyrogenic steam, and nitrided oxides were investigated utilizing MOS capacitors for time dependent dielectric breakdown (TDDB), dielectric field strength, and MOSFETs for inversion layer mobility measurements. The results show the C-face can achieve reliability similar to the Si-face, however this is highly dependent on the gate oxide process. The reliability is inversely related to the field effect mobility where other research groups report that pyrogenic steam yields the highest electron mobility while this work shows it has weakest oxide in terms of dielectric strength and shortest time to failure.

Abstract: In this work, the electrical characteristics and the reliability of 80nm thick deposited oxides annealed in NO and N2O on the 4H-SiC Si-face for gate oxide application in MOS devices is analyzed by C-V, I-V measurements and by constant current stress. Compared to thermally grown oxides, the deposited oxides annealed in N2O or NO showed improved electrical properties. Dit-values lower than 1011cm-2eV-1 have been achieved for the NO sample. The intrinsic QBD-values of deposited and annealed oxides are one order of magnitudes higher than the highest values reported for thermally grown oxides. Also MOSFETS were fabricated with a channel mobility of 20.05 cm2/Vs for the NO annealed deposited oxide. Furthermore annealing in NO is preferred to annealing in N2O regarding µFE- and QBD-values.

Abstract: The reliability of thermal oxides grown on n-type 4H-SiC C(000-1) face wafer has been investigated. In order to examine the influence of different oxidation atmospheres and temperatures on the reliability, metal-oxide-semiconductor capacitors were manufactured and the different oxides were characterized by C-V measurements and constant-current-stress. The N2O-oxides show the smallest flat band voltage shift compared to the ideal C-V curve and so the lowest number of effective oxide charges. They reveal also the lowest density of interface states in comparison to the other oxides grown on the C(000-1) face, but it is still higher than the best oxides on the Si(000-1) face. Higher oxidation temperatures result in smaller flat band voltage shifts and lower interface state densities. Time to breakdown measurements show that the charge-to-breakdown value of 63% cumulative failure for the N2O-oxide on the C(000-1) face is more than one order of magnitude higher than the highest values measured on the Si(000-1) face. Therefore it can be concluded that a smaller density of interface states results in a higher reliability of the oxide.