Oxidation of Polycrystalline Copper Thin Films at Ambient Conditions

Abstract

Qualitative and quantitative studies of the oxidation of polycrystalline copper (Cu) thin films upon exposure to ambient air conditions for long periods (on the order of several months) are reported in this work. Thin films of Cu, prepared by thermal evaporation, were analyzed by means of X-ray photoelectron spectroscopy (XPS) to gain an understanding on the growth mechanism of the surface oxide layer. Analysis of high-resolution Cu LMM, Cu2p3/2, and O1s spectra was used to follow the time dependence of individual oxide overlayer thicknesses as well as the overall oxide composite thickness. Transmission electron microscopy (TEM) and spectroscopic ellipsometry (SE) were used to confirm the results obtained from XPS measurements. Three main stages of copper oxide growth were observed: (a) the formation of a Cu2O layer, most likely due to Cu metal ionic transport toward the oxide−oxygen interface, (b) the formation of a Cu(OH)2 metastable overlayer, due to the interactions of Cu ions with hydroxyl groups present at the surface, and (c) the transformation of the Cu(OH)2 metastable phase to a more stable CuO layer. These three stages were found to occur simultaneously and to be mutually dependent on each other. The findings of this study may provide guidance in choosing the optimal conditions to fabricate and store copper-based ultra-large-scale integrated (ULSI) circuits.

Electrical Resistance Evolution of Cu Redistribution Layer Electroplated on a Si Interposer

“…This difference in the final phase reflects difference in the oxidation mechanism and driving force during the stage II and stage III. The last two stages of the overall Cu thin film oxidation mechanism explain the reason for the only and further formation of the Cu 2 O layer in the current work, which is compared to previous work mentioned earlier [16][17][18][19][20][21]. In any previous results, impurities in the polycrystalline Cu thin film and recrystallization of the polycrystalline Cu thin film during the proceeding of the Cu thin film oxidation have not been addressed on the effects of them on the oxidation mechanism and electrical resistance evolution of the Cu thin film.…”

“…(b) Little oxidation and little moving of Cu metal ions toward the oxide/oxygen interface occur but the resistance of RDL layer increases due to moving of chlorine ions (Cl-) toward oxide/metal interface instead of moving of Cu metal ions toward the oxide/oxygen interface to form a copper (II) hydroxide Cu(OH) 2 metastable phase as a wetting layer at the outer surface of the oxide layer, which was observed on the surface of polycrystalline Cu thin film evaporated thermally and exposed to ambient air conditions for long periods [21]. Simple calculations of the electrical resistivity (ρ) at different oxidation stages provide us with the information, summarized in …”

“…Note that no other oxide except copper (I) oxide, Cu 2 O was detected on Cu RDL film that was exposed to ambient air for 140 days, indicating that the only oxidation at all stages I, II, and III and further oxidation at stage III produced Cu 2 O. not detected in the XAES spectra of any of the film investigated. Based on the data of Ilia Platzman et al [21], the Cu(OH) 2 film was formed on the Cu 2 O layer at stage II, and thus CuO was obtained from the transformation of a Cu(OH) 2 metastable phase at stage III. This difference in the final phase reflects difference in the oxidation mechanism and driving force during the stage II and stage III.…”

Morphology‐controlled Electrodeposition of Copper Nanospheres onto FTO for Enhanced Photocatalytic Hydrogen Production

“…The fitted curve indicates the presence of the Cu species with peak centered at 567.95 eV, which can be attributed to the Cu 0 state, confirming that Cu exists on the FTO as the metallic phase. [45] This conclusion is also in good agreement with XRD and HRTEM results. Photoabsorption is one of the key factors affecting the photocatalytic performance of photocatalysts.…”

Facile preparation of 3D ordered mesoporous CuOx–CeO2 with notably enhanced efficiency for the low temperature oxidation of heteroatom-containing volatile organic compounds

“…The peaks in the Auger kinetic spectra at 917.6 and 914.6 eV correspond to Cu 2+ and Cu 1+ species, respectively. 63 The coexistence of Cu 1+ and Cu 2+ ions in the CuO-CeO 2 catalysts prepared using various methods have been previously reported. 27,60,62 Avgouropoulos et al 27 and Flytzani-Stephanopoulos et al 60 have proposed that Cu 1+ species result from the strong interactions of the Cu clusters with Ce oxide.…”