Reduced Electrical Defects and Improved Reliability of Atomic-Layer-Deposited HfO[sub 2] Dielectric Films by In Situ NH[sub 3] Injection

Abstract

The improvements in the reliability of HfO 2 thin films afforded by in situ NH 3 injection during their atomic layer depositions were studied. The NH 3 injection increased nitrogen content and reduced the residual carbon in the film, which resulted in the reduced leakage current density and improved reliabilities. A smaller flatband voltage shift, higher breakdown field, and the suppressed degradation of interface traps by constant voltage stress were obtained due to the solid SiN x interfacial layer formation, decreased carbon content, and reduction of electrical defects by oxygen vacancies. The solid interfacial SiN x layer improved the thermal stability of the films. Detailed analysis of the current-voltage characteristics revealed the electrical conduction behavior and nature of defects.It has been reported that the proper incorporation of nitrogen into HfO 2 films results in various improvements in its dielectric performance. 1,2 Especially, the SiN x interfacial layer, which is formed at the film/substrate interface when nitrogen is incorporated, is known to be an excellent barrier against the dielectric performance degradation caused by post-deposition annealing ͑PDA͒. To incorporate nitrogen in the films, the ex situ nitridation method has been used by means of either the thermal annealing process at high temperature or plasma treatment at lower temperatures under an NH 3 or N 2 O atmosphere. 3-6 However, these conventional nitridation methods still have several problems, such as the interfacial layer growth, interface and bulk trap increase by the thermal annealing, or plasma bombardment effect. Therefore, in this study, the dielectric characteristics and reliability of atomic layer deposited ͑ALD͒ HfO 2 thin films afforded by in situ NH 3 injection during the ALD were examined systemically. The changes in the chemical compositions of the films induced by in situ NH 3 injection, and their influences on the electrical properties, including conduction mechanisms and reliabilities of the HfO 2 films, were studied in detail. Although the in situ NH 3 injection for controlling the N concentration in the HfO 2 film is technically feasible and effective in improving the electrical performance as shown in this study, it has not been reported yet. ExperimentalHfO 2 films were grown to the thicknesses of ϳ5 nm on RCA-cleaned p-type Si͑100͒ substrates at 250°C using a travelingwave-type ALD reactor ͑Quros Co, Plus-200͒ using tetrakisdimethylamino-hafnium ͕Hf͓N͑CH 3 ͒ 2 ͔ 4 ͖ as an Hf precursor and ozone ͑O 3 ͒ with a concentration of 165 g/m 3 as an oxidant. NH 3 gas was injected during depositions in some cases, in which the ALD process sequences were Hf͓N͑CH 3 ͒ 2 ͔ 4 ͑2 s͒-Ar purge ͑10 s͒-O 3 ͑3 s͒-Ar purge ͑3 s͒-NH 3 ͑3 s͒-Ar purge ͑3 s͒ ͑named as sample Hf-O-N͒ and Hf͓N͑CH 3 ͒ 2 ͔ 4 -Ar purge-NH 3 -Ar purge-O 3 -Ar purge ͑named as sample Hf-N-O͒. The NH 3 gas flow rate was 200 sccm. The sample without the NH 3 injection was named as sample Hf-O. PDA was performed using a rapid thermal processing at 1000°C for ...

Impact of carbon and nitrogen impurities in high-κ dielectrics on metal-oxide-semiconductor devices

“…This is consistent with experiments that report improved electrical properties when N is incorporated in HfO 2 /Si MOS structures. [13][14][15] The overall features of III-As-based MOS structures are very similar to the case of oxide/Si MOS structures. The (þ1/0) level of C Al and (0/-1) level of C Hf occur near the CBM of InGaAs (0.11-0.28 eV above), and hence those impurities may act as a source of border traps and/or increase leakage current.…”

“…11,12 Nitrogen, on the other hand, has been found to lower the density of interface states and improve dielectric strength. [13][14][15] The role of impurities in the electrical properties of Al 2 O 3 has not been well explored.…”

Differences between direct current and alternating current capacitance nonlinearities in high-k dielectrics and their relation to hopping conduction

“…11 An activation energy around 0.3 eV was independently reported by other groups. 20,21 Since this activation energy was reported for low fields, it corresponds to R min (the shortest hopping distance is the one offering the lowest barrier, see Eq. (7), i.e., the favored path for dc conduction at low fields).…”

Atomic Layer Deposition Process of Hf‐Based High‐ k Gate Dielectric Film on Si Substrate

“…In addition, the nitrogen in the high-k film suppresses the leakage current density by passivating the electrical defects and improves the thermal stability, such as Si out-diffusion and crystallization temperature. The use of a reactant containing nitrogen, such as NH 3 , NH 4 OH, and low-temperature N 2 /O 2 mixture plasma enables to control the nitrogen profile in a high-k film without a high thermal budget and plasma damage during ALD growth [57][58][59][60]. On the other hand, the high thermal budget, serious plasma damage and excessive nitrogen incorporation at the interface by these postdeposition nitridation technique result in mobility degradation and impaired reliability [53,54].…”

“…Nitrogen incorporation is usually performed with thermal or plasma annealing using NH 3 or N 2 O gas [55,56]. The in situ Si(O)N x layer has several benefits, such as suppressed Si out-diffusion into the film, reduced leakage current density, and improved D it , as mentioned above [11,57]. The effectiveness of using a N-containing precursor (alkyl-amino precursors) in incorporating the interfacial Si(O)N x layer was discussed in detail above.…”