Influence of interlayer trapping and detrapping mechanisms on the electrical characterization of hafnium oxide/silicon nitride stacks on silicon

Abstract

Al/ HfO 2 / SiN x :H/ n-Si metal-insulator-semiconductor capacitors have been studied by electrical characterization. Films of silicon nitride were directly grown on n-type silicon substrates by electron cyclotron resonance assisted chemical vapor deposition. Silicon nitride thickness was varied from 3 to 6.6 nm. Afterwards, 12 nm thick hafnium oxide films were deposited by the highpressure sputtering approach. Interface quality was determined by using current-voltage, capacitance-voltage, deep-level transient spectroscopy ͑DLTS͒, conductance transients, and flatband voltage transient techniques. Leakage currents followed the Poole-Frenkel emission model in all cases. According to the simultaneous measurement of the high and low frequency capacitance voltage curves, the interface trap density obtained for all the samples is in the 10 11 cm −2 eV −1 range. However, a significant increase in this density of about two orders of magnitude was obtained by DLTS for the thinnest silicon nitride interfacial layers. In this work we probe that this increase is an artifact that must be attributed to traps existing at the HfO 2 / SiN x : H intralayer interface. These traps are more easily charged or discharged as this interface comes near to the substrate, that is, as thinner the SiN x : H interface layer is. The trapping/detrapping mechanism increases the capacitance transient and, in consequence, the DLTS measurements have contributions not only from the insulator/substrate interface but also from the HfO 2 / SiN x : H intralayer interface.

Electrical characterization of high-k based metal-insulator-semiconductor structures with negative resistance effect when using Al2O3 and nanolaminated films deposited on p-Si

“…faces can be charged or discharged, distorting the DLTS signal and overestimating the D it value 14,15. Here, ␤ PF is the Poole-Frenkel parameter, ⌬E A is the activation energy related to the PF emission, N DIGS is the DIGS density value, and B is the barrier height in the Fowler-Nordheim tunneling.…”

Negative-resistance effect in Al<inf>2</inf>O<inf>3</inf> based and nanolaminated MIS structures

“…On the other hand, the D it values of nanolaminated and Al 2 O 3 based structures should not appreciably differ because of the first high-k material in direct contact on silicon is Al 2 O 3 in both cases, i.e., the same Al 2 O 3 /Si interface is fabricated. However, we have observed that for stacked insulators, traps existing at different dielectric interfaces can be charged or discharged, distorting DLTS signal and overestimating the D it value [10][11]. This effect can be also identified from the conductance transient technique results leading to DIGS densities (N DIGS ) shown in Table I.…”

“…On the other hand, although aluminium oxide permittivity (10) is lower than hafnium oxide one (25), its gap is larger and has a barrier height higher with respect to silicon substrate and specifically, the use of Al 2 O 3 as a blocking layer in stacked structures induces a large voltage drop across the tunneling layer and enhances the operation speed of memory devices [4][5].…”

Electrical Characterization of High-Pressure Reactive Sputtered Sc2O3 Films on Silicon

“…We can see how DIGS states are preferentially located at energies in the range 50-100 meV under the silicon conduction band. Although DIGS densities are not too much high, these values may be higher than in unannealed samples (16).…”