Electrical Characterization of Defects Created by γ-Radiation in HfO2-Based MIS Structures for RRAM Applications

Abstract

The -radiation effects on the electrical characteristics of MIS capacitors based on HfO 2 , and on the resistive switching characteristics of the structures have been studied. The HfO 2 was grown directly on silicon substrates by atomic layer deposition. Some of the capacitors were submitted to a  ray irradiation using three different doses (16, 96 and 386 kGy). We studied the electrical characteristics in the pristine state of the capacitors. The radiation increased the interfacial state densities at the insulator/semiconductor interface, and the slow traps inside the insulator near the interface. However, the leakage current is not increased by the irradiation, and the conduction mechanism is Poole-Frenkel for all the samples. The switching characteristics were also studied, and no significant differences were obtained in the performance of the devices after having been irradiated, indicating that the fabricated capacitors present good radiation hardness for its use as a RS element.

Radiation Tolerance and Charge Trapping Enhancement of ALD HfO2/Al2O3 Nanolaminated Dielectrics

“…As shown, the radiation does not lead to an increase of the leakage current unlike the data reported in [ 20 , 21 ]. The results presented here seem to be more consistent with the findings published in [ 23 ], where no current deterioration is found. In fact, the irradiation with 10 kGy leads to a lower J for all stacks.…”

“…The results obtained for the as-grown and oxygen annealed HfO 2 /Al 2 O 3 stacks corroborate the reports [ 14 , 20 , 23 ] of higher radiation hardness of HfO 2 and HfO 2 /Al 2 O 3 -based MOS structures compared to the SiO 2 based ones. For these structures the effect of radiation mainly consists of a moderate positive oxide charge generation, and in accordance with [ 14 , 20 , 23 , 26 ] depending on the dose of γ radiation some improvement of the interface properties (reduction of slow interface states as well as fast interface states in the case of O 2 annealed samples) of high- k stack/Si system can be obtained. At the same time, the data for the N 2 treated samples suggest that the pre-irradiation processing affects the radiation response, most likely as a result of the different defect structure created under PDA in oxidizing and nitrogen containing ambient.…”

“…The devices in a radiation-intensive environment are subjected to the impact of high-energy particles and / or photons which may cause generation of various electrically active defects, leakage currents, early breakdown or loss of stored information. Despite the intensive investigations carried out recently [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], the radiation response of high- k -based metal-insulator-semiconductor (MIS) devices is far less understood compared to metal-SiO 2 -Si (MOS) structures. The radiation hardness of the alternative dielectrics and especially HfO 2 and Al 2 O 3 has been evaluated as comparable [ 12 , 13 ] or even better than that of SiO 2 [ 14 , 15 ] although the average dissipated energy during irradiation is much higher in HfO 2 than in SiO 2 layer that results in generation of more electron-hole pairs [ 16 , 17 ].…”

“…In the case of Al 2 O 3 and HfO 2 ; however, more complicated behavior is observed. Although some studies show an increase of D it with the dose [ 12 , 22 , 23 , 24 ], there are also reports that D it is not changed noticeably [ 20 , 25 ] and even studies demonstrating an improvement of D it values upon irradiation especially at low doses [ 14 , 26 , 27 , 28 ]. In contrast to SiO 2 , in the case of HfO 2 radiation-induced electron traps generation is also reported [ 25 ].…”

“…The investigations of leakage currents of Al 2 O 3 and HfO 2 films after irradiation also produce somehow contradictory results—a deterioration of the current-voltage ( J-V ) characteristics is obtained in [ 20 , 21 , 22 , 29 ] while other works do not find substantial radiation-induced change [ 23 , 30 ]. An improvement of the breakdown voltage is reported in [ 12 , 23 ]. It should also be noted that the radiation response of the complex dielectric stacks might be different compared to the dielectrics building the structure [ 21 ].…”