Hydrogenated amorphous silicon (a-Si:H) grown by PECVD has a lower loss tangent (tanδ) among conventional dielectrics(suchasSiO2 andSiNx)andhenceisconsideredasthebestamorphousdielectricmaterialforsuperconducting qubit application. The incorporation of PECVD a-Si:H into the Nb technology requires attention due to the possible degradationofthesuperconductivityoftheNbfilms. Superconductingtransitiontemperature(Tc)andresidualresistivity(ρ0)of20nm,50nmand100nmthickNbfilmsweremeasuredbeforeandaftera-Si:Hdeposition. Thepenetration ofoxygenandhydrogeninsidetheNbfilmswasevaluatedfromthevariationofthelatticeparameterobtainedbyX-ray diffraction. The high process temperature (250◦ C) and the presence of energetic hydrogen ions during the a-Si:H layer growthcausedadecreaseofTc andincreaseofρ0 throughtwophysicalprocesses: 1)oxygendiffusionfromthesurface Nb oxides and 2) hydrogen diffusion inside the Nb films. The degradation of Tc was reduced with the increase of the filmthickness. NitridationofNbfilmsanddepositionofasputteredthinamorphoussiliconlayer(a-Si)ontheNbfilms (in both cases made in situ after the Nb film deposition) were investigated as surface treatments to protect the Nb films during PECVD. It was demonstrated that both methods markedly reduce oxygen and hydrogen diffusion into Nb films during a-Si:H deposition, but the a-Si layer was more effective to protect the Nb films.
Investigation of the superconducting properties of Nb films covered with PECVD a-Si:H layers for superconducting qubit application / A., Bruno; Mengucci, Paolo; L. V., Mercaldo; M. P., Lisitskiy. - In: PHYSICS PROCEDIA. - ISSN 1875-3892. - 36:(2012), pp. 239-244.
Investigation of the superconducting properties of Nb films covered with PECVD a-Si:H layers for superconducting qubit application
MENGUCCI, Paolo;
2012-01-01
Abstract
Hydrogenated amorphous silicon (a-Si:H) grown by PECVD has a lower loss tangent (tanδ) among conventional dielectrics(suchasSiO2 andSiNx)andhenceisconsideredasthebestamorphousdielectricmaterialforsuperconducting qubit application. The incorporation of PECVD a-Si:H into the Nb technology requires attention due to the possible degradationofthesuperconductivityoftheNbfilms. Superconductingtransitiontemperature(Tc)andresidualresistivity(ρ0)of20nm,50nmand100nmthickNbfilmsweremeasuredbeforeandaftera-Si:Hdeposition. Thepenetration ofoxygenandhydrogeninsidetheNbfilmswasevaluatedfromthevariationofthelatticeparameterobtainedbyX-ray diffraction. The high process temperature (250◦ C) and the presence of energetic hydrogen ions during the a-Si:H layer growthcausedadecreaseofTc andincreaseofρ0 throughtwophysicalprocesses: 1)oxygendiffusionfromthesurface Nb oxides and 2) hydrogen diffusion inside the Nb films. The degradation of Tc was reduced with the increase of the filmthickness. NitridationofNbfilmsanddepositionofasputteredthinamorphoussiliconlayer(a-Si)ontheNbfilms (in both cases made in situ after the Nb film deposition) were investigated as surface treatments to protect the Nb films during PECVD. It was demonstrated that both methods markedly reduce oxygen and hydrogen diffusion into Nb films during a-Si:H deposition, but the a-Si layer was more effective to protect the Nb films.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
