Thin Solid Films 587 (2015) 20–27Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf Inductive couple plasma reactive ion etching characteristics of TiO2 thin films Adrian Adalberto Garay, Su Min Hwang, Chee Won Chung ⁎ Department of Chemistry and Chemical Engineering, Center for Design and Applications of Molecular Catalysts, Inha University, 100 Inharo, Nam-gu, Incheon 402-751, Republic of Korea a r t i c l e i n f o Available online 22 November 2014 Keywords: Titanium dioxide Thin films Inductively coupled plasma reactive ion etching HBr/Ar gas Cl2/Ar gas C2F6/Ar gas Hard mask a b s t r a c t Changes in the inductively coupled plasma reactive ion etching characteristics of TiO2 thin films in response to the addition of HBr, Cl2 and C2F6 to Ar gas were investigated. As the HBr, Cl2 and C2F6 concentration increased, the etch rate increased; however, the etch profile degree of anisotropy followed a different trend. As HBr concentration increased, the greatest anisotropic etch profile was obtained at 100% HBr, while the greatest anisotropic etch profile was obtained at concentrations of 25% when etching was conducted under C2F6 and Cl2. Field emission scanning electron microscopy revealed that 25% C2F6 generated the greatest vertical etch profile; hence, etch parameters were varied at this concentration. The effects of rf power, dc-bias voltage and gas pressure on the etch rate and etch profile were also investigated. The etch rate and degree of anisotropy in the etch profile increased with increasing rf power and dc-bias voltage and decreasing gas pressure. X-ray photoelectron spectroscopy analysis of the films etched under a C2F6/Ar gas mixture revealed the existence of etch byproducts containing F (i.e. TiFx) over the film. CxFy compounds were not detected on the film surface, probably due to contamination with atmospheric carbon. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The etching of electronic materials is a crucial step in the fabrication of semiconductor devices because improper conditions can lead to defects such as faceting, trenching, redeposition, and plasma damage to the film. There has been a continuous and rapid implementation of new techniques and materials that could improve the scalability and performance of these devices owing to a rapid density growth and physical limitations of semiconductor storage devices [1]. Conventional inorganic hard masks such as SiO2 and SiC cannot be employed in the next generation of electronic devices owing to their low selectivity and severe faceting during etching. Metallic and organic hard mask materials have been proposed as possible replacements for previously conventional inorganic hard masks owing to their better hard mask capabilities [2]. The etching of hard mask materials such as Ta, Ti, TiN and TiO2 under several etch chemistries has recently been widely investigated [3,4]. TiO2 has received a great deal of attention due to its numerous applications in solar cells, light-emitting diodes, photo catalysts, photosplitting of water and gas sensors [5,6]. In the semiconductor industry, TiO2 has been proposed as a replacement for SiO2 dielectrics of capacitors owing to its high dielectric constant and low leakage current [7,8], ⁎ Corresponding author at: 244E, 2nd building, Inha University, 100 Inharo, Nam-gu, Incheon, 402-751, Republic of Korea. Tel: +82 32 860 7473; fax: +82 32 872 0959. E-mail address:
[email protected] (C.W. Chung). http://dx.doi.org/10.1016/j.tsf.2014.11.055 0040-6090/© 2014 Elsevier B.V. All rights reserved. and as a hard mask material owing to its high selectivity and strong adhesion. The etch properties of TiO2 thin films under an inductively coupled plasma (ICP) were previously investigated under Cl2, HBr, BCl3, CF4 and non-corrosive gases such as CH4/H2/Ar. The results of these studies indicated that, as the concentration of halogen gas in the gas mixture increases, the etch rate increases and aggressive etch parameters appear to produce further improvement of the etch rate and etch profile [9–12]. The etch rates, etch selectivity, plasma modeling, etch mechanisms and surface analysis of TiO2 thin films have previously been discussed [9–13], but physical evidence of redeposition-free etch profiles with a high degree of anisotropy is scarce. Development of nanoscale anisotropic etching processes for TiO2 thin films and their characterization is necessary for their future applications in semiconductor devices and as a hard mask material. In this study, we investigated the inductively coupled plasma reactive ion etching (ICPRIE) of TiO2 thin films. The etch rate and etch profile of a variety of gases (Cl2, HBr, C2F6, Ar) were examined, and the effects of etch parameters including coil rf power, dc-bias voltage, gas pressure and gas concentration on the etch profile and etch mechanism were investigated. The etch rates were obtained using a surface profilometer and etch profiles were observed by field emission scanning electron microscopy (FESEM). Additionally, the surface chemistry of TiO2 films under the proper etch gas was analyzed by X-ray photoelectron spectroscopy (XPS). all samples were Argon pre-sputtered for 30 s at beam acceleration energy and beam current of 1 keV and 2 μA. Fig. probably due to the absence of any chemical reactions and the dominance of physical sputtering. PR patterned TiO2 thin films before etching are shown in Fig.67 Pa. 6(b)) revealed an etch slope with a high degree of anisotropy. The HBr/Ar. Cl2/Ar and C2F6/Ar gas mixtures. then decreased to 116. 2. FESEM micrographs that describe the etch profile of TiO2 thin films etched under various HBr concentrations are shown in Fig. over the surface. The films were patterned as parallel lines of different widths.08 at 100% Ar that gradually decreased to its minimum value of 0.02 nm/min at 100% Ar to a maximum of 105.6 nm/min. a cold fluid around 12 °C to 15 °C was circulated through the susceptor.12 nm/min. Etch rate of TiO2 thin films and PR. 1 shows the etch rate of TiO2 thin films and the etch selectivity of TiO2 over PR etched under the HBr/Ar gas mixture. At 100% HBr.A. It is believed that the etch selectivity of TiO2 film over PR mask can somehow influence the overall etch profile. Garay et al. / Thin Solid Films 587 (2015) 20–27 200 2. The etch rate slowly increased from a minimum of 23. Experimental details 3. while circular void channels between the substrate and the susceptor were filled with He to improve sample cooling. 4(c) to (d)).08 at 100% Ar to a minimum of 0. while the addition of 25% C2F6 to Ar gas (Fig. Although an unsaturated fluorocarbon protective layer is formed when the films are etched in a C2F6/Ar plasma. Fig.2 nm/min at 100% C2F6. At 100% HBr (Fig. 3 depicts the etch rate of TiO2 thin films and the etch selectivity of TiO2 over PR etched under a Cl2/Ar gas mixture. The etch rate of TiO2 and PR increased from a minimum of 23. the introduction of 25% HBr was sufficient to obtain a slanted. while the etch rate increased. The binding energies were calibrated using Au 4f7/2 = 84.00 eV as a reference. 2(a). The sample etched in pure Ar showed heavy sidewall redeposition.197 at 25% HBr. the etch slope clearly improved relative to other samples. increased from 25% to 75% (Fig. Additionally. Etch byproducts. Fig. The etch selectivity gradually decreased from a maximum of 1.2 nm/min at 100% HBr. after which it increased to a maximum value of 0. the effects of etch parameters such as ICP rf power.7–4) × 10−4 Pa. The etch rates. Photolithography was carried out on TiO2 thin films using a 1. These findings suggest the existence of a polymer layer. We consider this decrease in etch rate of TiO2 thin films at 100% HBr to be related to plasma instabilities and/or the considerable reduction of ion bombardment onto the sample due to the absence of Ar gas. The etch selectivity of TiO2 thin films over PR mask showed the tendency of slightly decreasing with increasing C2F6 concentration. dc bias voltage of 300 V and gas pressure of 0. dcbias voltage to the substrate. Results and discussion Etching of TiO2 thin films was carried out under various HBr/Ar. Fig. Fig. The TiO2 thin films were then etched using a conventional ICPRIE system (A-Tech System. To control the kinetic energy of the ions generated on the plasma. Heavy sidewall redeposition and a slanted slope could clearly be seen. To dissipate the heat generated during the etching process while avoiding damage to the sample. respectively. while the profile of the sample etched at 25% Cl2 improved considerably. the etch rate of PR is so fast that the sidewall of TiO2 cannot be properly protected. 4(a) and (b) shows the transition of the etch profile from 100% Ar and 25% Cl2/Ar. the etch slope became more slanted and the surface roughness increased considerably. the surface chemistry and etch mechanism of TiO2 films under the proper etch gas were analyzed by using an ex-situ K-alpha source XPS analyzer (ThermoScientific K-Alpha). As HBr concentrations 2 TiO2 PR TiO2/PR 150 100 1 Selectivity Etch Rate (nm/min) ICPRIE of TiO2 thin films was conducted using HBr/Ar. presumably containing CxFy compounds.81 nm/min at 100% Ar gas to a maximum of 64. respectively.08 nm/min under pure argon to a minimum of 0. Etch by products and the surface chemistry of TiO2 films prepared under the proper etch gas were analyzed by XPS. Additionally. High density plasma was generated by a coil located at the top of the main chamber. etch selectivity and etch profiles of the TiO2 thin film and photoresist were examined under varying concentrations of HBr/Ar.A. the etch rate decreased to 63. Cl2/Ar and C2F6/Ar.81 nm/min at 100% Ar gas to a maximum of 134. 100 nm TiO2 thin films were prepared on a SiO2/Si substrate by rf magnetron reactive sputtering using a Ti target in a Ar (35 sccm)/O2 (5 sccm) atmosphere. 1. The vacuum condition of the main chamber was generated by a turbo molecular pump backed up by a mechanical pump. In general. Cl2/ Ar and C2F6/Ar concentrations at an ICP power of 800 W. making it possible to obtain base pressures lower than (2.02 nm/min under pure Ar to a maximum of 160. but redeposition free etch profile that improved as concentration increased. respectively. A further increase in Cl2 concentration led to negative effects on the etch profile degree of anisotropy (Fig. the formation of an area near the sidewall that differed in height from the rest of the film was clearly evident. 5 shows the etch rate and selectivity of the TiO2 thin films etched under C2F6/Ar gas mixture at varying concentrations. there was a slight improvement in the etch slope and no redeposition could be seen near the sidewall. The etch selectivity showed a maximum value of 1. 6(a)).02 nm/min to a maximum of 447.56 MHz rf power supply.667 Pa.56 MHz that was capacitively coupled to the susceptor.6 nm/min and 221.81 nm/min and 22.2 μm thick photoresist (PR: AZ1512) to pattern the film. but the angle was still less than 60°. The etch rate increased from a minimum of 23. As the C2F6 concentration increased from 50% to 100% (Fig. 6 shows the FESEM micrographs of the TiO2 samples etched under a variety of C2F6 concentrations.62 nm/min at 75% HBr gas. The TiO2 samples etched in pure Ar showed heavy sidewall redeposition (Fig. Fig. but the etch . Cl2/Ar and C2F6/Ar gas mixtures used as etch gases were fed into the main chamber at a rate of 40 sccm. All XPS analysis samples were TiO2 thin films without photoresist. The etch rate of PR underwent a steeper increase from a minimum of 22. that was connected to a 13. dc-bias voltage to substrate of 300 V and gas pressure of 0. To remove any contamination from the film surface. At 100% C2F6. 6(c) to (e)). and gas pressure on the etch rate and profile were investigated. The etch selectivity underwent a rapid decrease from 1. The etch rates were obtained using a surface profilometer (Tencor P1) and etch profiles were observed by FESEM (FESEM-Hitachi 4300SE) at an operating voltage of 15 kV. Korea) equipped with a main chamber and a load lock chamber. and etch selectivity of TiO2/PR under varying TiO2 concentrations in HBr/Ar mixtures and the following etch conditions: ICP rf power of 800 W.3 at 100% Cl2. All halogen gas chemistries explored above showed a chemical enhancement of the TiO2 etch rate over pure Ar sputtering. Fig. 21 50 0 0 25 50 75 100 0 % HBr in HBr/Ar Fig. 2(b) shows the etch profile of TiO2 thin films etched in pure Argon. The etch rate of PR increased from a minimum of 22. 2(f)). 4 depicts the FESEM micrographs of the TiO2 thin films etched under various Cl2/Ar concentrations.543 at 100% HBr.477 at 100% C2F6. 2(c) to (e)). a selfinduced dc bias voltage was generated by an rf power generator at 13.3 nm/min at 25% HBr.76 nm/min at 100% Cl2. and (f) 100% HBr. followed by C2F6/Ar and HBr/Ar. 7(a) shows the etch rates of TiO2 thin films and PR together with the selectivity of TiO2 thin films to PR for a variation of ICP power while the other conditions were fixed. which helps maintain the high degree of anisotropy in the etch slope. Garay et al. which brings into question the reasons why the etch rates of TiO2 thin films etched under a C2F6/Ar gas mixture were considerably lower than those obtained under a Cl2/Ar gas mixture [9].. The 500 2 PR TiO2/PR 400 300 1 200 Selectivity Etch Rate (nm/min) TiO2 100 0 0 25 50 75 100 0 % Cl2 in Cl2/Ar Fig. as well as the higher volatility of TiClx etch byproducts compared to TiBrx etch by products [11].67 Pa. We believe that there is a balance between the formation of an inhibition layer and its removal by the effect of Ar sputtering at this concentration. Both Cl2/Ar and HBr/Ar appear to follow an ion enhanced etching mechanism commonly known as reactive ion etching [14]. and etch selectivity of TiO2/PR under varying TiO2 concentrations in Cl2/Ar mixtures and the following etch conditions: ICP rf power of 800 W. the etch rates of TiO2 thin films and PR increased . dc-bias voltage to substrate of 300 V and gas pressure of 0. As the ICP rf power increased from 700 W to 900 W.667 Pa. Fig. 3. etch rates of TiO2 thin films under SF6/Ar gas mixtures have been reported to be much faster than those under Cl2/Ar gas mixtures. C2F6 and CHF4) that yield unsaturated polymer-forming species in plasmas [14].g. / Thin Solid Films 587 (2015) 20–27 (a) (b) 300nm Photoresist TiO2 SiO2 TiO2 (d) (c) (e) (f) Fig.A. (c) 25% HBr. similar to those generated in response to freon feed gases (e. rate of TiO2 thin films in Cl2/Ar was the fastest. FESEM micrographs of TiO2 thin films before etching (a) and etched in (b) pure argon. We believe that etching of TiO2 thin films in a C2F6/Ar gas mixture is hindered by the formation of an inhibition layer over the film. (e) 75% HBr. 25% C2F6 was selected as the standard gas concentration for evaluation of the etching parameters due to its degree of anisotropy and plasma stability. The SEM micrographs of the TiO2 thin films etched under HBr/Ar. Etch rate of TiO2 thin films and PR.22 A. 2. (d) 50% HBr. Based on the results obtained upon etching of TiO2 thin films in varying gas mixtures and concentrations. The high etch rates in the Cl2/Ar gas mixture may be associated with the higher total flux of neutral reactive species. Cl2/Ar and C2F6/Ar revealed that the best etch profile was obtained at 25% C2F6/Ar. dc bias voltage of 300 V and gas pressure of 0. The standard conditions were 25% C2F6 in a C2F6/Ar gas mixture at an ICP rf power of 800 W. 8(a). As the DC bias increased from 200 V to 400 V. increase in the etch rate of TiO2 thin films [12]. FESEM micrographs of TiO2 thin films etched in (a) pure argon. The etch slope at a dc-bias voltage of 400 V (Fig. The etch selectivity of TiO2 thin films to PR steadily increased from 200 V to 300 V. and etch selectivity increased slightly. and etch selectivity of TiO2/PR under varying TiO2 concentrations in C2F6/Ar mixtures and the following etch conditions: ICP rf power of 800 W.A. 7(d)). 4. 7(c) depicts the sample etched at 800 W (standard conditions). / Thin Solid Films 587 (2015) 20–27 23 (b) (a) 300nm (c) (d) (e) Fig. the etch rate of both TiO2 thin films and PR rapidly increased relative to the rf power variation. 8(c)) was steeper than that at 200 V. resulting in an increased etch rate and improved etch profile. The etch profile seemed to be similar to those observed in response to varying C2F6/Ar concentrations. The increase in rf power causes increases in the densities and fluxes of positive ions and F atoms through an increase in both dissociation and ionization rates.A. (c) 50% Cl2. The etch profile of the sample etched at 700 W shows a slanted etch slope with no redeposition near the sidewall (Fig. and (e) 100% Cl2. Fig. 5. the etch slope appeared to improve slightly compared to TiO2 thin films etched at 800 W. suggesting good reproducibility. 8(b)). . 7(b)). The increase in the etch rate of TiO2 thin films as rf power increased can be attributed to an increase of both neutral species and ions.667 Pa. As the rf power increased to 900 W (Fig. which leads to an 200 1 100 0 0 25 50 75 100 Selectivity Etch Rate (nm/min) 2 TiO2 PR TiO2/PR 0 % C2F6 in C2F6/Ar Fig. but a further increase in the dc bias to 400 V caused a decrease in the etch selectivity. (b) 25% Cl2. The increase in dc-bias voltage caused an increase in the overall ion energy. FESEM micrographs revealed that the etch slope became slanted and the etch depth near the sidewall differed greatly from the average etch depth at a dc-bias voltage of 200 V (Fig. This caused an expedited increase in the sputtering effect of the film that enhanced the bond breaking and desorption of etch products from the TiO2 surface. increasing the ion bombardment onto the film surface. Garay et al. dc bias voltage of 300 V and gas pressure of 0. 7(b) to (d). Etch rate of TiO2 thin films and PR. The effects of dc-bias voltage on the etch rates and selectivity of the TiO2 thin films and PR are presented in Fig. (d) 75% Cl2. FESEM micrographs of TiO2 thin films etched at various ICP rf powers are shown in Fig. 133 Pa).133 Pa to 1. (d) 75% C2F6. The narrow scan of the as-deposited film reveals the chemical state of pure TiO2 (~458. We suspect that the increase in neutral active species (chemical etching) at high pressures results in the formation of a polymer layer over the film. 9(b)) revealed a steep etch slope with no visible redeposition along the sidewall. Conversely. The SEM micrograph of the sample etched at 0. At low pressures (0. and (e) 100% C2F6.33 Pa (Fig. / Thin Solid Films 587 (2015) 20–27 (a) (b) 300nm (c) (d) (e) Fig. 10(a) shows the narrow scan of Ti 2p3/2 peaks for TiO2 thin films.16]. while the etch profile of the sample etched at 1. the main Ti 2p3/2 peak shifted to a higher energy of around 459 eV. Garay et al. As pressure increased from 0. The shift of the peak indicates that compounds containing Ti were formed on the surface of TiO2 thin films [12]. ion bombardment onto the sample is enhanced because high energy and low incident angle ions are abundant due to the large mean free path. FESEM micrographs of TiO2 thin films etched in (a) pure argon. when the TiO2 thin films were etched in 25% C2F6/Ar (low C2F6 concentration) and 75% C2F6 (high C2F6 concentration). Fig. the existence of main peaks of 684. XPS analysis was conducted to elucidate the etch mechanism and determine whether etch byproducts were present on films etched under a C2F6/Ar gas mixture. In addition to the existence of TiFx or TiO2 − xFx compounds after etching of TiO2 thin films in a C2F6/Ar gas mixture. 9(a) shows the etch rate and selectivity of TiO2 thin films etched at different gas pressures. 6. lowering the pressure leads to a proportional decrease in the concentration of neutral etchant.8 eV) and Ti2O3 (~456. while the relative rate of energetic ion-enhanced etching increases [15]. at high pressures (1.9 eV) [17].8 eV suggests the presence of structures corresponding to oxyfluoride (F–Ti–O) functional groups over the TiO2 surface [19]. Additionally. The lack of high energy ions and diminished ion bombardment consequently reduce the etch rate due to inefficient Ti–O bond breaking and/or the formation of a greater amount of etch byproducts. which reduces the etch rate and degree of anisotropy of the etch profile [14. This results in an increased etch rate and degree of anisotropy of the etch profile. 10(b) presents the narrow scans of the F 1s peaks.33 Pa.1 eV after the sample was etched in 25% and 75% C2F6/Ar gas mixtures suggests the existence of TiFx compounds over the film [18]. (b) 25% C2F6.33 Pa). we expected to obtain signals corresponding to CxFy . 9(c)) exhibited a slanted etch slope. while the etch selectivity of TiO2 over PR decreased slightly.133 Pa (Fig. Fig. Fig. the etch rate of the TiO2 thin films and PR decreased. the presence of secondary peaks located at approximately 683.A.5 eV to 685. Bare TiO2 thin films without photoresist masks were used for the analysis and all species were pre-sputtered prior to analysis to remove contaminants from the surface. The F 1s peaks of the as-deposited film were not observed.24 A. However. however. (c) 50% C2F6. In general. many ions with relatively low energy and high-incident angles exist. Conclusions The ICPRIE characteristics of PR patterned TiO2 thin films were investigated using HBr/Ar. Cl2 and C2F6 concentrations. which was likely due to the formation of a much denser layer of etch byproducts (TiFx compounds. Furthermore. oxyfluorides. the etch slope appeared to be greater than 80°. the etch rates of TiO2 thin film and PR increased. 7. reported that fluorinated carbon residues over the film were extremely difficult to detect unless in situ XPS measurements were carried out after etching [20].A. the degree of anisotropy increased while for Cl2 and C2F6 it decreased as concentration increased. FESEM micrographs of TiO2 thin films etched at the following coil rf power: (b) 700 W. with . (a) Etch rate of TiO2 thin films and PR. The destruction of Ti–O bonds by ion sputtering generated highly reactive sites that not only increased the chemical etching rate of the C2F6 neutral species. / Thin Solid Films 587 (2015) 20–27 1 TiO2 (a) PR TiO2/PR 200 Selectivity Etch Rate (nm/min) 250 25 150 100 50 0 700 800 900 0 rf power (b) (c) 300nm (d) Fig. At 25% C2F6. O and/or F containing compounds formed over the film.A. Generally. Ti. Garay et al. but also induced bonding between the Ti and O elements of the film to form several types of Ti oxides. 4. as the HBr. the most anisotropic etch profiles were obtained in a C2F6/Ar gas mixture. etc. Cl2 and C2F6 concentration in the Ar gas mixture increased. even at low C2F6 concentrations (Figs. (c) 800 W.) over the film at high C2F6 concentrations.667 Pa. Cl2/Ar and C2F6/Ar gas mixtures. Hazra et al. Even though the etch rate increased as the C2F6 concentration increased. 6(b) and 10). but as the HBr concentration increased. FESEM images revealed heavy sidewall redeposition on the TiO2 samples etched in pure Ar. however. Cl2/Ar and C2F6/Ar gas mixtures was found to follow the conventional reactive ion etching mechanism. compounds. The etching of TiO2 thin films using HBr/Ar. detailed inspection of Fig. 6 FESEM micrographs clearly showed that the TiO2 surface became irregular and rougher as the C2F6 concentration increased. except for the HBr/Ar gas mixture. Among the three halogen gases employed. and (d) 900 W. The Ti 2p3/2 and F 1s spectra confirmed that F related compounds were formed over the TiO2 layer after etching under C2F6 plasma chemistries. the Ti 2p3/2 and C 1s narrow scan (figure not shown) revealed the absence of this etch byproduct. 10(a)) Ti2O3 peak intensity increased with C2F6 addition compared to the as deposited film. CxFy polymers. and etch selectivity of TiO2/PR under varying coil rf power and the following etch conditions: 25% C2F6 in C2F6/Ar gas mixture. The etch rates and etch profiles of TiO2 thin films were examined by individually varying the HBr. The Ti 2p3/2 spectrum (Fig. dc bias voltage of 300 V and gas pressure of 0. Garay et al. FESEM micrographs of TiO2 thin films etched at varying gas pressures of: (b) 0.133 Pa and (c) 1. (a) Etch rate of TiO2 thin films and PR. 8. . and etch selectivity of TiO2/PR under varying gas pressures and etch conditions of: 25% C2F6 in C2F6/Ar gas mixture. 1 (a) TiO2 PR TiO2/PR 200 Selectivity Etch Rate (nm/min) 250 150 100 50 0 0 5 10 0 Pressure (b) (c) 300nm Fig. / Thin Solid Films 587 (2015) 20–27 TiO2 200 1 (a) PR TiO2/PR 150 Selectivity Etch Rate (nm/min) 250 100 50 0 200 300 400 0 dc bias (b) (c) 300nm Fig. 9.667 Pa. ICP rf power of 900 W and dc bias voltage of 300 V. ICP rf power of 900 W and gas pressure of 0.26 A. and etch selectivity of TiO2/PR under varying dc-bias voltage and etch conditions of: 25% C2F6 in C2F6/Ar gas mixture. FESEM micrographs of TiO2 thin films etched at the following coil rf power: (b) 200 V and (c) 400 V.33 Pa. (a) Etch rate of TiO2 thin films and PR.A. 1989. Jaehong Park.H. even though post treatment of the films might be necessary to reduce or eliminate fluorine etch byproducts from the film. Pearton. 13 (2012) 144. Sci. mainly TiFx compounds. Vac. K. as the concentration increased to pure C2F6. Thin TiO2 film prepared by low pressure chemical vapor deposition. [18] P.S. Daniel L. Appl. 10. Technol. Sci. 31 (2003) 703. Oehrlein. XPS analysis of partially etched TiO2 blanket films confirmed that the chemical reaction between TiO2 and C2F6 left etch byproducts. Matsuo. Guerin.J. structure and crystallinity of anodized TiO2 nanotubes. Young-Hee Joo. Joubert. 50047). Vacuum 86 (2012) 2152. Jeong. Dong-Il “Dan” Cho. Vac. 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