Study Of HfO₂ Gate Interface Characteristics And Irradiation Effect Of Strained MOS

Strain and high k gate technology are important means of continuing the Moore’s law. By combining such two techniques, it can not only effectively improve the working speed of integrated circuits, but also can reduce the static power consumption caused by the gate leakage current, which is an effective way of improving the performance of integrated circuits. At the same time, with the expansion of the application scope of strained devices and circuits, their irradiation characteristics, which are becoming more and more important, have become a new research hotspot. Based on the experimental measurements and theoretical modeling and simulation, this paper is mainly focused on the high k gate interface characteristics of strained MOS and total dose irradiation effect.The factors that influence the gate interface characteristics and gate current of strained MOS with Hf O2 high k gate dielectric were analyzed in this paper. Hf O2 strained MOS samples were prepared by ALD technology, and the annealing experiments and the electric stress tests were carried out respectively for the samples. And based on MOS high frequency C-V characteristics and the experimental measurements of gate current Ig~Vg characteristic, the gate interface characteristics and the gate current of strained MOS with Hf O2 high k gate dielectric were mainly studied. The results show that high temperature annealing, which though causes a slight reduction of Hf O2 high k dielectric constant, can significantly reduce the quantity of the gate oxide trap charges and interface charges. As a result, high temperature annealing reduces the gate leakage current, and improves the gate interface characteristics and the device reliability. However, electric stress experiments show that the negative pressure stress has little impact on the gate current, but the positive pressure stress can cause a significant decrease in the gate leakage current. It is mainly due to the increase of electronic F-P launch barrier height relied on the oxide traps, which causes the tunneling inhibition and leads to a great reduction of the gate current. Therefore, after high temperature annealing, Hf O2 strained MOS shows good gate interface characteristics, and the gate current is smaller. As a result, the device performance is further improved.Based on the action mechanism and the physical process of the irradiation on strained Si PMOS, a physical model for describing the total dose irradiation effects was established. An analytical model of reflecting the degradation of threshold voltage was also established under the total dose gamma irradiation. And a simulation was performed. The simulation results show that the strained Si PMOS’s threshold voltage drifts continuously and output saturation current decreases greatly with the increase of irradiation total dose, while the transconductance and the mobility of devices has decreased significantly. Moreover, the thickness of gate oxygen layer and the channel doping conentrationhave have a great influence on the threshold voltage with the same irradiation total dose. At last, the irradiation experiments were carried out and the corresponding experimental testing results were compared with the simulation results. The results show that they are consistent with each other, which proves the accuracy of this model.