In-situ XPS Investigation of ALD Cu2O and Cu Thin Films after Successive Reduction

• Main Authors: Dhakal, Dileep, Waechtler, Thomas, E. Schulz, Stefan, Mothes, Robert, Moeckel, Stefan, Lang, Heinrich, Gessner, Thomas
• Other Authors: TU Chemnitz, Center for Microtechnologies
• Format: Others
• Language: English
• Published: Universitätsbibliothek Chemnitz 2014
• Subjects: Atomic Layer Deposition (ALD); Cuprous Oxide (Cu2O); X-ray Photoelectron Spectroscopy (XPS); Surface Chemistry; ddc:540; ddc:620; Röntgen-Photoelektronenspektroskopie; Oberflächenchemie
• Online Access: http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-147043; http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-147043; http://www.qucosa.de/fileadmin/data/qucosa/documents/14704/Dileep_Dhakal_In-situ_XPS_investgation_of_ALD.pdf; http://www.qucosa.de/fileadmin/data/qucosa/documents/14704/signatur.txt.asc

This talk was presented in the 14th International Conference on Atomic Layer Deposition (ALD 2014) in Kyoto, Japan on 18th June 2014. Abstract Atomic Layer Deposition (ALD) is emerging as a ubiquitous method for the deposition of conformal and homogeneous ultra-thin films on complex topographies and large substrates in microelectronics. Electrochemical deposition (ECD) is the first choice for the deposition of copper (Cu) into the trenches and vias of the interconnect system for ULSI circuits. The ECD of Cu necessitates an electrically conductive seed layer for filling the interconnect structures. ALD is now considered as a solution for conformal deposition of Cu seed layers on very high aspect ratio (AR) structures also for technology nodes below 20 nm, since physical vapor deposition is not applicable for structures with high AR. Cu seed layer deposition by the reduction of Cu2O, which has been deposited from the Cu(I) β-diketonate [(nBu3P)2Cu(acac)] (1) used as Cu precursor, has been successfully carried out on different substrates like Ta, TaN, SiO2, and Ru [1, 2]. It was found that the subsequent gas-phase reduction of the Cu2O films can be aided by introducing catalytic amounts of a Ru precursor into the Cu precursor, so that metallic copper films could potentially obtained also on non-catalytic substrates [3, 4]. In this work, in situ X-ray photoelectron spectroscopy (XPS) investigation of the surface chemistry during Cu2O ALD from the mixture of 99 mol % of 1 and 1 mol % of [Ru(η5 C5H4SiMe3)(η5-C7H11)] (2) as ruthenium precursor, and the reduction of Cu2O to metallic Cu by formic acid carried out on SiO2 substrate are demonstrated. Oxidation states of the Cu in the film are identified by comparing the Cu Auger parameter (α) [5] with literature data. α calculated after ALD equals 362.2 eV and after reduction equals 363.8 eV, comparable to the Cu2O and metallic Cu in thin-films [6] respectively. In addition, <10 % of Cu(I), Cu(II), and Cu(OH)2 species are identified from the Cu 2p3/2 and Cu L3VV Auger spectrum after reduction. Consequently, the ALD Cu2O is successfully reduced to metallic copper by in-situ thermal reduction using formic acid. [1] T. Waechtler et al., J. Electrochem. Soc., 156 (6), H453 (2009). [2] T. Waechtler et al., Microelectron. Eng., 88, 684 (2011). [3] S. Mueller et al., Conference Proceedings SCD 2011, Semiconductor Conference Dresden, pp. 1-4. [4] T. Waechtler et al., US Patent Application Publication, US 2013/0062768. [5] C. D. Wagner, Faraday Discuss. Chem. Soc., 60, 291 (1975). [6] J. P. Espinós et al., J. Phys. Chem. B, 106, 6921 (2002).