Low power fluorine plasma effects on electrical reliability of AlGaN/GaN high electron mobility transistor

The new electrical degradation phenomenon of the AlGaN/GaN high electron mobility transistor（HEMT） treated by low power fluorine plasma is discovered. The saturated current, on-resistance, threshold voltage, gate leakage and breakdown voltage show that each experiences a significant change in a short time stress, and then keeps unchangeable. The migration phenomenon of fluorine ions is further validated by the electron redistribution and breakdown voltage enhancement after off-state stress. These results suggest that the low power fluorine implant ion stays in an unstable state. It causes the electrical properties of AlGaN/GaN HEMT to present early degradation. A new migration and degradation mechanism of the low power fluorine implant ion under the off-stress electrical stress is proposed. The low power fluorine ions would drift at the beginning of the off-state stress, and then accumulate between gate and drain nearby the gate side. Due to the strong electronegativity of fluorine, the accumulation of the front fluorine ions would prevent the subsequent fluorine ions from drifting, thereby alleviating further the degradation of AlGaN/GaN HEMT electrical properties.

Influence of nitrogen dose on the charge density of nitrogen-implanted buried oxide in SOI wafers

To harden silicon-on-insulator（SOI） wafers fabricated using separation by implanted oxygen（SIMOX） to total-dose irradiation,the technique of nitrogen implantation into the buried oxide（BOX） layer of SIMOX wafers can be used.However,in this work,it has been found that all the nitrogen-implanted BOX layers reveal greater initial positive charge densities,which increased with increasing nitrogen implantation dose.Also,the results indicate that excessively large nitrogen implantation dose reduced the radiation tolerance of BOX for its high initial positive charge density. The bigger initial positive charge densities can be ascribed to the accumulation of implanted nitrogen near the Si-BOX interface after annealing.On the other hand,in our work,it has also been observed that,unlike nitrogen-implanted BOX,all the fluorine-implanted BOX layers show a negative charge density.To obtain the initial charge densities of the BOX layers,the tested samples were fabricated with a metal-BOX-silicon（MBS） structure based on SIMOX wafers for high-frequency capacitance-voltage（C-V） analysis.