Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee Research paper Study on efect of complexing agents on Co oxidation/dissolution for chemical-mechanical polishing and cleaning process Ohsung Kwon a,1 , KiHo Bae b,1 , Jinuk Byun a , Taeho Lim c, ⁎ , Jae Jeong Kim a, ⁎ a School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea b Semiconductor R&D Center, Samsung Electronics Co., Ltd., Hwaseong, Gyeonggi 18448, Republic of Korea c Department of Chemical Engineering, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul 06978, Republic of Korea ARTICLEINFO Keywords: Cobalt Dissolution Surface oxide Complexing agent ABSTRACT The efect of complexing agents on Co oxidation/dissolution in alkaline solution was investigated for Co che- mical-mechanical polishing (CMP) and post-CMP cleaning processes. The oxidation and dissolution properties of Co in a solution are greatly afected by complexing agents, which could infuence the performance of Co CMP and post-CMP cleaning processes. Herein, three complexing agents, glycine, ethylenediaminetetraacetic acid (EDTA), and citric acid were studied. It was revealed that the complexing agents determined Co dissolution rate dependingonthepresenceorabsenceofH 2 O 2 .GlycineshowedahigherCodissolutionratethanEDTAandcitric acid in the absence of H 2 O 2 , while EDTA showed the highest dissolution rate in the presence of H 2 O 2 . Negligible dissolution was observed with citric acid, regardless of the presence of H 2 O 2 . Electrochemical impedance and UV–Vis spectroscopies found that the diference in Co dissolution rates was related to Co oxidation rate and complexation capability of each complexing agent. Glycine showed a higher Co oxidation rate than EDTA, while EDTA had a much higher complexation capability than glycine. Citric acid exhibited the lowest Co oxidation rate and complexation capability, resulting in the slowest Co dissolution rate. 1. Introduction The high resistivity of conventional W-based middle-of-the-line (MOL) local interconnects and contacts becomes a signifcant problem as the semiconductor process scales down to the dimension below 10nm[1,2]. The high resistivity of W, generally deposited by chemical vapor deposition (CVD), has negative efects on response time, energy consumption, and thermal dissipation of semiconductor devices [3]. Therefore, a necessity of developing new contact material has been raised recently. Co, having lower electron mean free path compared to W[4], is now considered as a next-generation interconnect and contact material in small-scaled devices [5,6].Therehavebeensomeresearches to replace W with Co [7–10]. Kamineni et al. reported the frst use of CVD Co as a MOL local interconnect material, showing its potential as alternatives to W [10]. In the case where Co is introduced as interconnect and contact material in semiconductor process, the chemical and physical changes of Co in subsequent processes must be understood. Thus, the char- acteristics of Co have been extensively investigated, especially re- garding polishing and corrosion properties which are mainly related to chemical-mechanical polishing (CMP) [11–17]. A few researches on post-CMP cleaning process for Co have been also reported, mainly fo- cusing on corrosion inhibition properties of specifc cleaning solutions [18–20]. Since Co (Young's modulus: 209 GPa) can easily be damaged by abrasives like silica particles (88.7 GPa) in CMP process, it is ne- cessary to form Co oxides (119.68 GPa) by continuously oxidizing Co surface during the process to minimize the surface damage [21–23]. A certain level of Co oxide dissolution is also desirable in order to achieve a uniform surface during CMP process. A similar strategy is applied to the post-CMP cleaning process, except that the dissolution of Co oxides isacriticalstepinremovingimpuritiesfromtheCosurface.Thus,inthe context of chemical reactions, both CMP and post-CMP cleaning pro- cesses are based upon the oxidation and dissolution reactions of Co surface [24,25]. The basic mechanisms of CMP and post-CMP cleaning processes consist of surface oxidation, mechanical abrasion (CMP pro- cess only), and chemical dissolution of the oxidized surface. In general, Co is mostly covered with Co(II) hydroxide (Co(OH) 2 ) [26,27]. These Co(II) compounds are naturally formed on the Co sur- face at atmospheric condition, stably passivating the surface from fur- ther oxidation. There may be also small amounts of Co(III) compounds https://doi.org/10.1016/j.mee.2020.111308 Received 5 August 2019; Received in revised form 19 December 2019; Accepted 30 March 2020 ⁎ Corresponding authors. E-mail addresses: taeholim@ssu.ac.kr (T. Lim), jjkimm@snu.ac.kr (J.J. Kim). 1 These authors contributed equally to this manuscript. Microelectronic Engineering 227 (2020) 111308 Available online 01 April 2020 0167-9317/ © 2020 Elsevier B.V. All rights reserved. T