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Article

Mechanical Properties and Diffusion Barrier Performance of CrWN Coatings Fabricated through Hybrid HiPIMS/RFMS

by
Li-Chun Chang
1,2,*,
Cheng-En Wu
1 and
Tzu-Yu Ou
1
1
Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan
2
Center for Plasma and Thin Film Technologies, Ming Chi University of Technology, New Taipei City 24301, Taiwan
*
Author to whom correspondence should be addressed.
Coatings 2021, 11(6), 690; https://doi.org/10.3390/coatings11060690
Submission received: 15 May 2021 / Revised: 3 June 2021 / Accepted: 7 June 2021 / Published: 9 June 2021
(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)
Browse Figures
Versions Notes

Abstract

:
CrWN coatings were fabricated through a hybrid high-power impulse magnetron sputtering/radio-frequency magnetron sputtering technique. The phase structures, mechanical properties, and tribological characteristics of CrWN coatings prepared with various nitrogen flow ratios (fN2s) were investigated. The results indicated that the CrWN coatings prepared at fN2 levels of 0.1 and 0.2 exhibited a Cr2N phase, whereas the coatings prepared at fN2 levels of 0.3 and 0.4 exhibited a CrN phase. These CrWN coatings exhibited hardness values of 16.7–20.2 GPa and Young’s modulus levels of 268–296 GPa, which indicated higher mechanical properties than those of coatings with similar residual stresses prepared through conventional direct current magnetron sputtering. Face-centered cubic (fcc) Cr51W2N47 coatings with a residual stress of −0.53 GPa exhibited the highest wear and scratch resistance. Furthermore, the diffusion barrier performance of fcc CrWN films on Cu metallization was explored, and they exhibited excellent barrier characteristics up to 650 °C.

1. Introduction

Transition metal nitride films such as TiN [1], CrN [2,3], TaN [4,5], and W2N [6,7] have been widely utilized as protective coatings in versatile applications, such as hard coatings, diffusion barriers, and corrosion-resistant and wear-resistant layers. Moreover, ternary nitride films such as TiAlN [8], TaZrN [9,10], and CrWN [11] have been developed to enhance the characteristics of the above binary nitride materials. CrWN coatings have been applied as hard coatings [11,12,13,14,15] and protective coatings on die materials for precision molding glass technology [16,17,18,19]. In a previous study [15], CrWN coatings manufactured using direct current magnetron sputtering (DCMS) exhibited a wide hardness range of 10.8–27.6 GPa depending on their chemical composition and crystalline structure. The operation of precision molding glass requires molding dies and protective coatings against repeated thermal cycles at 200–600 °C under a low oxygen content atmosphere, implying that CrWN possesses the potential to function as a diffusion barrier for Cu metallization. Cu is the most favorable material for interconnecting ultra-large-scale integrated circuits because of its higher conductivity and superior electromigration resistance compared to Al [20]. Cu diffuses easily into Si and SiO2, which compromises device performance [21,22]. Barrier materials that have been reported to prohibit the diffusion of Cu into Si include transition metals (Cr, Ti, Nb, Ta, and W) [23], bilayers (Ta/Ti) [24], alloys (TiW) [25,26], binary and ternary nitrides (TiNx, TaNx, WNx, RuWN, and WTiN) [26,27,28,29,30,31,32], thin film metallic glass (Zr–Cu–Ni–Al–N) [33], and high entropy alloys [34]; and the failure temperatures of these barrier layers exhibited distinct variations in the range of 400–850 °C. Therefore, the successful exploration of new barrier materials is essential in the field of integrated circuits. A qualifying barrier material should exhibit good adhesion to Cu, prevent the diffusion of Cu into Si or the interlayer dielectric (ILD), and be inactive on both Cu and ILD at high temperatures. CrN has been extensively used for mechanical and corrosion resistance purposes; however, previous reports on its use as a diffusion barrier are scarce [35,36]. CrN can decompose to Cr2N by releasing N2 at temperatures of 500–700 °C because of stress relaxation [37]. W can also be added to CrN to increase oxidation resistance and thermal stability [16,18]. Therefore, the goal of this study was to investigate the mechanical properties and diffusion barrier performance of CrWN coatings.
High-power impulse magnetron sputtering (HiPIMS) exhibits a main feature of a high degree of ionization of sputtered material through the development of a highly dense plasma (~1013 ions/cm3) [38,39,40,41]. The HiPIMS technique is typified by a low duty cycle of <10%, low repetition frequency of <10 kHz, and high-power densities in the order of kW/cm2 [42]. Therefore, HiPIMS helps to produce coatings with a dense structure and high hardness [43,44]. Moreover, a hybrid HiPIMS/radio-frequency magnetron sputtering (RFMS) process has been previously employed to simultaneously improve the deposition rate and coating quality [45,46]. In this paper, CrWN films were prepared by hybrid HiPIMS/RFMS, the Cu/CrWN/Cr/Si structures were annealed in a vacuum (7 × 10−4 Pa) at elevated temperatures for 1 h, and the thermal stability and diffusion barrier characteristics of the CrWN barriers were studied.

2. Materials and Methods

In a hybrid HiPIMS/RFMS apparatus, a target of W (99.95%, 50.8 mm in diameter) was linked to a RF power generator, whereas the target of Cr (99.99%, 76.2 mm in diameter) was attached to a pulse power supply (SPIK 2000A; Shen Chang Electric Co., Ltd., Taipei, Taiwan). The distance between substrates and targets was 12 cm. The substrate holder was rotated at 10 rpm and grounded. In the first part of this study, a Cr interlayer of 100 nm was deposited at 200 W for 10 min under an Ar flow of 30 sccm. Then, CrWN coatings were co-sputtered on Cr interlayers, after flowing N2 and Ar into the vacuum chamber. The total flow rate of N2 and Ar was 30 sccm. The nitrogen flow ratio (fN2 = N2/(N2+Ar)), ranging from 0.1 to 0.4, was the main process variable. The working pressure was maintained at 0.4 Pa. The power applied to the W (WW) and Cr (WCr) targets was 50 and 500 W, respectively. The deposition times were controlled to form coatings of approximately 1000 nm in thickness. The substrates were silicon and stainless-steel (SUS420) plates. The samples prepared on SUS420 substrates were adopted to evaluate the tribological characteristics, adhesion properties, and wear behavior. Adhesion was tested via a scratch test (Scratch Tester, J & L Tech. Co., Gyeonggi-do, Korea) with a diamond tip 0.2 mm in diameter at a moving speed of 0.01 mm/s. Wear behavior was examined through a pin-on-disc test method with a pin of cemented carbide (WC-6 wt.% Co) and a ball 6 mm in diameter under a normal load of 2 N. The sliding speed was 126 mm/s, the wear track diameter was 4 mm, and the wear length was 200 m. In the second part of this work, two CrWN thin films of 100 nm with a Cr interlayer of 10 nm were fabricated by shortening the deposition times to evaluate their diffusion barrier characteristics, including sheet resistance, phase stability, and elemental diffusion. These samples were covered with a Cu layer (100 nm thick) prepared through DCMS and annealed in a vacuum (7 × 10−4 Pa) at 550–650 °C for 1 h.
The elemental compositions were analyzed using a field-emission electron probe microanalyzer (FE-EPMA, JXA-8500F, JEOL, Akishima, Japan). The phases were identified through grazing-incident X-ray diffraction (GIXRD) using an X-ray diffractometer (X’Pert PRO MPD, PANalytical, Almelo, the Netherlands). Coating thicknesses were examined via cross-sectional images using a field emission scanning electron microscope (FE-SEM, JSM-6701F, JEOL, Akishima, Japan). The nanostructure was observed using transmission electron microscopy (TEM, JEM-2010F, JEOL, Akishima, Japan). The mechanical properties, hardness (H), and Young’s modulus (E) of the coatings were evaluated using a nanoindentation tester (TI-900 Triboindenter, Hysitron, Minneapolis, MN, USA) and determined using the Oliver and Pharr method [47]. An atomic force microscope (AFM, DI 3100, Bruker, Santa Barbara, CA, USA) recorded the average roughness (Ra) and root-mean-square roughness (Rq). The residual stress of coatings was estimated using the curvature method [48],
σ f t f = E S h S 2 6 ( 1 − ν S ) R f ,
where σf is the in-plane stress component in the film, tf is the film thickness, ES is the Young’s modulus of the Si substrate (130.2 GPa), νS is the Poisson’s ratio for the Si substrate (0.279), hS is the substrate thickness (525 μm), and Rf is the curvature radius of the film. Wear scars and elemental mapping were observed using SEM (S3400N, Hitachi, Tokyo, Japan) equipped with energy dispersive spectroscopy (EDS, Inca x-sight, Oxford Instruments, Tokyo, Japan). The sheet resistance of the Cu/CrWN/Cr/Si samples was determined using a four-point probe. The sheet resistance can be derived by:
R = 4.53   V I ,
where I is the applied current, and V is the measured voltage. The elemental diffusion was examined using an Auger electron spectroscopy (AES, PHI700, ULVAC-PHI, Kanagawa, Japan).

3. Results and Discussion

3.1. CrWN Coatings Co-Sputtered Using Various Nitrogen Flow Rates

Table 1 lists the atomic compositions of the CrWN coatings prepared with an fN2 of 0.1–0.4. These samples were denoted as Cr65W4N31, Cr62W3N35, Cr58W2N40, and Cr51W2N47 in accordance with their atomic compositions. The N content of the CrWN coatings were increased from 31.0 to 35.0, 39.4, and 46.9 at.% by increasing the nitrogen flow ratio (fN2) from 0.1 to 0.2, 0.3, and 0.4, whereas the Cr content exhibited a tendency to decrease from 64.7 to 61.9, 58.1, and 50.6 at.%, and the W content decreased from 4.0 to 2.8, 2.2, and 2.0 at.%. The O contents of these coatings were 0.3 at.%. The deposition rate increased from 12.1 to 14.6 nm/min and then decreased to 11.4 and 10.9 nm/min as fN2 increased from 0.1 to 0.4 (Table 1).
Figure 1 shows the GIXRD patterns of the CrWN coatings. The coatings prepared with an fN2 of 0.1 and 0.2 exhibited a hexagonal Cr2N phase, whereas the coatings prepared with an fN2 of 0.3 and 0.4 displayed a face-centered cubic (fcc) CrN phase. As the formation enthalpy of W2N ( ∆ H 298 0 = −72 kJ/mol) is lower than that of CrN (−118 kJ/mol) and Cr2N (−126 kJ/mol) [6,49], and the W content is low compared to the Cr content, the evolution of the crystalline phase is dominated by the compositions of Cr and N. The phase evolution from Cr2N to CrN was accompanied by a decrease in the atomic ratio of Cr/N from 2.09, to 1.77, 1.47, and 1.08 when the fN2 increased from 0.1, to 0.2, 0.3, and 0.4. Moreover, the reflection Cr2N (111) of the Cr62W3N35 coatings shifted toward a lower value compared to that of the Cr65W4N31 coatings, which implies that higher amounts of N atoms were incorporated into the lattice, resulting in an increase in lattice constants. A similar variation was observed in the reflections CrN (111) and (200) of the Cr51W2N47 coatings compared to those of the Cr58W2N40 coatings.
Figure 2 shows the cross-sectional FE-SEM images of the CrWN coatings. The Cr65W4N31 coatings revealed an evident columnar structure, whereas the Cr62W3N35 coatings displayed a much fine columnar structure. By contrast, the Cr58W2N40, and Cr51W2N47 costings with a CrN phase exhibited short and disordered grains, similar to those reported by Lin et al. [50]. Figure 3a displays a cross-sectional TEM (XTEM) image of the Cr51W2N47 coatings, which exhibited a dense and granular structure. The grain size was tens of nanometers. The selected area electron diffraction pattern exhibited CrN (111) and (200) spots. Figure 3b shows lattice fringes of 0.236 and 0.207 nm belonging to d-spacings of CrN (111) and (200), respectively. Figure 4 depicts the Ra and Rq values of the CrWN coatings. Ra and Rq exhibited constant values of 2.4–3.0 and 3.1–3.8 nm, respectively. These roughness values were low compared to those (Ra: 2.3–6.1 nm, Rq: 2.9–7.6 nm) of CrWN coatings prepared through DCMS accompanied with an atomic ratio Cr/W > 1 and an fcc phase [15,18]. These results indicate that the films fabricated by HiPIMS/RFMS formed a dense structure and a smooth surface. The films with a columnar structure could promote Cu diffusion through the grain boundaries [27]; therefore, the characteristics of the Cr51W2N47 coatings when used as a diffusion barrier were further investigated and are discussed in the next section.
Figure 5 shows the mechanical properties of the CrWN coatings. The variation in mechanical properties with N content revealed the combined effects of the phase and residual stress. Figure 6 displays the residual stress of CrWN coatings, which shows a tendency to vary from tensile (1.30 GPa) to compressive stress (−0.53 GPa) when the N content is increased. Compressive residual stress was beneficial for increasing the hardness [18,51,52]. Figure 7a shows the relationship between the hardness and the residual stress of CrWN coatings. Selected data from a previous study [15] on DCMS-prepared CrWN coatings dominated by a Cr2N or CrN phase are shown in Figure 7a for comparison. The hardness and residual stress reveal a linear fitting trend. Figure 7b shows the relationship between Young’s modulus and residual stress, and reveals a lower fitting slope compared to those shown in Figure 7a. Therefore, the Cr62W3N35 coatings showed higher H and E values than those of the Cr65W4N31 coatings, whereas the Cr51W2N47 coatings exhibited higher H and E values than those of the Cr58W2N40 coatings. However, the H values of the Cr62W3N35 and Cr51W2N47 coatings were 20.2 and 19.7 GPa, respectively, implying that the H was affected by their phase structures. The Cr62W3N35 coatings crystallized into a Cr2N phase, whereas the Cr51W2N47 coatings formed a CrN phase. Previous studies [53,54,55] have reported that Cr2N is harder than CrN, both in bulk and film form, because of the higher covalent bonding character of Cr2N. Hirota et al. [53] reported hardness values of 14.5 and 11.2 GPa for ceramic Cr2N and CrN, respectively. Hones et al. [54] reported values of 28 and 18 GPa for sputtered Cr2N and CrN films, respectively, whereas 16.1 and 12.5 GPa were obtained in the work of Wei et al. [55]. In a previous study [15], CrWN coatings with a high W content of 31–57 at.% and fabricated through DCMS revealed an fcc structure and high compressive residual stress in the range from −2.1 to −3.0 GPa, accompanied by a high H of 21.1–27.1 GPa and a high E of 241–310 GPa. By contrast, the Cr51W2N47 coatings prepared through DCMS exhibited a columnar structure accompanied by a low H of 10.8 GPa, a low E of 168 GPa, a high Ra of 6.1 nm, a high Rq of 7.6 nm, and a tensile stress of 0.54 GPa [18]. The DCMS–Cr51W2N47 coatings exhibited a loose and columnar structure, with a (111) orientation [18], whereas the HiPIMS/RFMS-Cr51W2N47 coatings revealed a dense and granular structure (Figure 3) with a weak (200) orientation (Figure 1). Hones et al. [11] suggested a small quantity of W stabilized CrWN coatings with a similar weak (200) orientation. Martine et al. [2] reported that CrN films with (200) and (111) orientations demonstrated hardness levels of 18 and 12–14 GPa, respectively. The hybrid HiPIMS/RFMS process in this study enhanced the mechanical properties of the Cr51W2N47 coatings, even though the W content was low.
Figure 8 shows the H/E and H3/E2 ratios of the CrWN coatings. H/E represents the indicator of elastic strain to failure [56], whereas H3/E2 denotes the resistance against plastic deformation [57]. The H3/E2 and residual stress exhibited a linear fitting trend (Figure 7a) similar to those of H and H/E (not shown in this paper) against residual stress. H/E and H3/E2 were suggested as pointers for fracture toughness, which affected the wear resistance [58]. However, such correlations between H/E and H3/E2 for toughness were compatible with hard coatings with low plasticity [59]. Figure 9 shows the wear scars of the CrWN coatings. Chippings marks were observed along the wear track of the Cr65W4N31 coatings. The elemental mapping of Cr and N indicated that the coating was worn out, whereas the Fe signal revealed the exposure of the SUS420 substrate. Similar wear behavior was shown for the Cr62W3N35 and Cr58W2N40 coatings with narrow wear widths. The results of wear tests indicated that the Cr65W4N31, Cr62W3N35, and Cr58W2N40 coatings were exhausted with a wear length of 200 m, whereas the Cr51W2N47 coatings exhibited a low wear rate of 1.4 × 10−6 mm3·N−1·m−1 with a coefficient of friction of 0.60. The DCMS-prepared CrWN coatings with an H ≤ 19.1 GPa were worn through after wear tests, and the coatings with H values of 20.3–27.0 GPa exhibited wear rates of 3.1–12 × 10−6 mm3·N−1·m−1 [15]. Figure 10 shows the scratch scars of the CrWN coatings. LC1 and LC2 presented loads inducing cohesive failure and exposing the substrate, respectively [60]. The Cr65W4N31 coatings exhibited the lowest LC1 and LC2 values among the tested samples, implying their brittleness. Severe chipping was observed for the Cr65W4N31 coatings after the normal load reached the LC1. Slight chipping was found on the Cr62W3N35 and Cr58W2N40 coatings, whereas almost no chipping was detected on the Cr51W2N47 coatings. The distinct deviations in wear and scratch tests could be attributed to the effect of residual stress. The Cr65W4N31 coatings exhibited a high tensile residual stress (1.30 GPa), whereas the Cr51W2N47 coatings demonstrated a compressive residual stress (−0.53 GPa). The LC1 was 2 N for the Cr65W4N31 coatings and 5–7 N for the other three coatings. The LC1 and H/E values of these CrWN coatings exhibited similar trends. The LC2 increased from 6 N for the Cr65W4N31 coatings to 15, 22, and 25 N for the Cr62W3N35, Cr58W2N40, and Cr51W2N47 coatings, respectively, implying that the Cr51W2N47 coatings possessed the highest adhesion strength, agreeing with a high wear resistance. The Cr51W2N47 coating exhibited the superior mechanical properties and tribological characteristics among the surveyed CrWN coatings.

3.2. Diffusion Barriers

Table 2 lists the atomic compositions of the two CrWN films prepared at a thickness of approximately 100 nm and used as diffusion barriers for Cu metallization. In Section 3.1, the coatings prepared using WCr = 500 W, WW = 50 W, fN2 = 0.4, and a deposition time of 85.6 min exhibited a composition of Cr51W2N47, whereas the composition became Cr59W2N39 as the deposition time was reduced to 6.7 min. This result can be attributed to the overestimation of Cr content because of a low thickness of 108 nm for the CrWN films accompanied by a Cr interlayer of 10 nm. In addition, the Cr54W6N40 samples were prepared using a higher WW of 100 W. Figure 11 shows the sheet resistance of the Cu/CrWN/Cr/Si samples. The 550 °C annealed samples exhibited lower sheet resistances than those at the as-deposited state, which was attributed to the defect annihilation and grain growth of Cu films [29,61]. The sheet resistance increased slightly when the samples were annealed at 600 and 650 °C, whereas an abrupt increase was observed when the annealing temperature was set to 700 °C, which implied the formation of Cu3Si [61]. Figure 12 and Figure 13 show the GIXRD patterns of the Cu/Cr59W2N39/Cr/Si and Cu/Cr54W6N40/Cr/Si samples annealed at 550–650 °C, respectively, and no reflection from Cu-silicide is observed. The as-deposited samples exhibited CrN and Cu phases, whereas a Cr2N phase was observed after annealing at 550–650 °C. The diffusion barrier performance of the Cu/CrWN/Cr/Si samples was further examined through the AES depth profiles of the annealed samples.
Figure 14 and Figure 15 show the AES depth profiles of the as-deposited and annealed Cu/Cr59W2N39/Cr/Si and Cu/Cr54W6N40/Cr/Si samples, respectively. The main variation between the as-deposited and annealed samples occurred at the interlayer. The original Cr interlayer evolved into an interdiffusion zone consisting of Cr, N, and Si. The interdiffusion between Si/Cr interface was reported at 450 °C [62]. Cu diffused into a shallow depth of the CrWN films at 650 °C. The CrWN films played the role of a diffusion barrier up to 650 °C after annealing for 1 h.

4. Conclusions

CrWN coatings were successively fabricated through a hybrid HiPIMS/RFMS process. The N content of the CrWN coatings increased when the fN2 was increased, accompanied by structural variation from the Cr2N to CrN phase. The principal conclusions of this study can be summarized as:
  • The hybrid HiPIMS/RFMS process formed CrWN coatings with a dense structure and a smooth surface.
  • The mechanical properties, hardness and Young’s modulus, of the CrWN coatings were affected by the crystalline phase and residual stress. The Cr51W2N47 coatings exhibited a granular structure, revealing enhanced mechanical properties (H: 19.7 GPa, E: 296 GPa) and reduced surface roughness values (Ra: 2.6 nm, Rq: 3.3 nm), accompanied by a compressive residual stress of −0.53 GPa.
  • The tribological characteristics, wear resistance, and scratch behavior of the CrWN coatings were affected by residual stress. The Cr51W2N47 coatings with a compressive residual stress exhibited superior tribological characteristics compared to those CrWN coatings revealing tensile residual stresses.
  • The application of CrWN films as a diffusion barrier on Cu metallization was practiced by annealing up to 650 °C in a vacuum for 1 h.

Author Contributions

Conceptualization, L.-C.C.; validation, L.-C.C.; investigation, C.-E.W. and T.-Y.O.; resources, L.-C.C.; writing-original draft preparation, L.-C.C.; project administration, L.-C.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Ministry of Science and Technology, Taiwan, grant numbers 108-2221-E-131-012 and 109-2622-E-131-003-CC3. The APC was funded by Ming Chi University of Technology.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The technical support of the Instrumentation Center at the National Tsing Hua University with the AES and EPMA analyses is greatly appreciated.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Shin, C.S.; Gall, N.; Hellgren, N.; Patscheider, J.; Petrov, I.; Greene, J.E. Vacancy hardening in single-crystal TiNx (001) layers. J. Appl. Phys. 2003, 93, 6025–6028. [Google Scholar] [CrossRef] [Green Version]
  2. Martinez, E.; Sanjinés, R.; Banakh, O.; Lévy, F. Electrical, optical and mechanical properties of sputtered CrNy and Cr1−xSixN1.02 thin films. Thin Solid Films 2004, 447, 332–336. [Google Scholar] [CrossRef]
  3. Kong, J.Z.; Xu, P.; Cao, Y.Q.; Li, A.D.; Wang, Q.Z.; Zhou, F. Improved corrosion protection of CrN hard coating on steel sealed with TiOxNy–TiN composite layers. Surf. Coat. Technol. 2020, 381, 125108. [Google Scholar] [CrossRef]
  4. Liu, X.; Ma, G.J.; Sun, G.; Duan, Y.P.; Liu, S.H. Effect of deposition and annealing temperature on mechanical properties of TaN film. Appl. Surf. Sci. 2011, 258, 1033–1037. [Google Scholar] [CrossRef]
  5. Liu, K.Y.; Lee, J.W.; Wu, F.B. Fabrication and tribological behavior of sputtering TaN coatings. Surf. Coat. Technol. 2014, 259, 123–128. [Google Scholar] [CrossRef]
  6. Hones, P.; Martin, N.; Regula, M.; Lévy, F. Structural and mechanical properties of chromium nitride, molybdenum nitride, and tungsten nitride thin films. J. Phys. D Appl. Phys. 2003, 36, 1023–1029. [Google Scholar] [CrossRef]
  7. Lou, B.S.; Moirangthem, I.; Lee, J.W. Fabrication of tungsten nitride thin films by superimposed HiPIMS and MF system: Effects of nitrogen flow rate. Surf. Coat. Technol. 2020, 393, 125743. [Google Scholar] [CrossRef]
  8. Zhou, M.; Makino, Y.; Nose, M.; Nogi, K. Phase transition and properties of Ti–Al–N thin films prepared by r.f.-plasma assisted magnetron sputtering. Thin Solid Films 1999, 339, 203–208. [Google Scholar] [CrossRef]
  9. Aouadi, S.M.; Filip, P.; Debessai, M. Characterization of tantalum zirconium nitride sputter-deposited nanocrystalline coatings. Surf. Coat. Technol. 2004, 187, 177–184. [Google Scholar] [CrossRef]
  10. Chang, L.C.; Chang, C.Y.; Chen, Y.I. Mechanical properties and oxidation resistance of reactively sputtered Ta1–xZrxNy thin films. Surf. Coat. Technol. 2015, 280, 27–36. [Google Scholar] [CrossRef]
  11. Hones, P.; Consiglio, R.; Randall, N.; Lévy, F. Mechanical properties of hard chromium tungsten nitride coatings. Surf. Coat. Technol. 2000, 125, 179–184. [Google Scholar] [CrossRef]
  12. Wu, F.B.; Tien, S.K.; Duh, J.G. Manufacture, microstructure and mechanical properties of CrWN and CrN/WN nanolayered coatings. Surf. Coat. Technol. 2005, 200, 1514–1518. [Google Scholar] [CrossRef] [Green Version]
  13. Yao, S.H.; Su, Y.L.; Kao, W.H.; Cheng, K.W. Evaluation on wear behavior of Cr–Ag–N and Cr–W–N PVD nanocomposite coatings using two different types of tribometer. Surf. Coat. Technol. 2006, 201, 2520–2526. [Google Scholar] [CrossRef]
  14. Wu, W.Y.; Wu, C.H.; Xiao, B.H.; Yang, T.X.; Lin, S.Y.; Chen, P.H.; Chang, C.L. Microstructure, mechanical and tribological properties of CrWN films deposited by DC magnetron sputtering. Vacuum 2013, 87, 209–212. [Google Scholar] [CrossRef]
  15. Chang, L.C.; Zheng, Y.Z.; Gao, Y.X.; Chen, Y.I. Mechanical properties and oxidation resistance of sputtered Cr–W–N coatings. Surf. Coat. Technol. 2017, 320, 196–200. [Google Scholar] [CrossRef]
  16. Lin, C.H.; Duh, J.G.; Yau, B.S. Processing of chromium tungsten nitride hard coatings for glass molding. Surf. Coat. Technol. 2006, 201, 1316–1322. [Google Scholar] [CrossRef]
  17. Lin, T.N.; Han, S.; Weng, K.W.; Lee, C.T. Investigation on the structural and mechanical properties of anti-sticking sputtered tungsten chromium nitride films. Thin Solid Films 2013, 529, 333–337. [Google Scholar] [CrossRef]
  18. Chen, Y.I.; Cheng, Y.R.; Chang, L.C.; Lee, J.W. Chemical inertness of Cr–W–N coatings in glass molding. Thin Solid Films 2015, 593, 102–109. [Google Scholar] [CrossRef]
  19. Huang, A.; Xie, Z.; Li, K.; Chen, Q.; Chen, Y.; Gong, F. Thermal stability of CrWN glass molding coatings after vacuum annealing. Coatings 2020, 10, 198. [Google Scholar] [CrossRef] [Green Version]
  20. Nitta, T.; Ohmi, T.; Hoshi, T.; Sakai, S.; Sakaibara, K.; Imai, S.; Shibata, T. Evaluating the large electromigration resistance of copper interconnects employing a newly developed accelerated life-test method. J. Electrochem. Soc. 1993, 140, 1131–1137. [Google Scholar] [CrossRef]
  21. McBrayer, J.D.; Swanson, R.M.; Sigmon, T.W. Diffusion of Metals in Silicon Dioxide. J. Electrochem. Soc. 1986, 133, 1242–1246. [Google Scholar] [CrossRef]
  22. Istratov, A.A.; Flink, C.; Hieslmair, H.; Weber, E.R. Intrinsic diffusion coefficient of interstitial copper in silicon. Phys. Rev. Lett. 1998, 81, 1243–1246. [Google Scholar] [CrossRef]
  23. Ono, H.; Nakano, T.; Ohta, T. Diffusion barrier effects of transition metals for Cu/M/Si multilayers (M = Cr, Ti, Nb, Mo, Ta, W). Appl. Phys. Lett. 1994, 64, 1511–1513. [Google Scholar] [CrossRef]
  24. Shang, J.; Hao, J.X.; Hang, T.; Li, M. Diffusion barrier effect of Ta/Ti bilayer in organic dielectric/Cu interconnects. Thin Solid Films 2018, 653, 113–118. [Google Scholar] [CrossRef]
  25. Wang, H.W.; Chiou, B.S. Barrier layer effect of titanium-tungsten on the electromigration in sputtered copper films on polyimide. J. Mater. Sci. Mater. Electron. 2000, 11, 17–24. [Google Scholar] [CrossRef]
  26. Fugger, M.; Plappert, M.; Schäffer, C.; Humbel, O.; Hutter, H.; Danninger, H.; Nowottnick, M. Comparison of WTi and WTi(N) as diffusion barriers for Al and Cu metallization on Si with respect to thermal stability and diffusion behavior of Ti. Microelectron. Reliab. 2014, 54, 2487–2493. [Google Scholar] [CrossRef]
  27. Takeyama, M.B.; Sato, M.; Aoyagi, E.; Noya, A. Preparation of ultrathin TiNx films by radical assisted low temperature deposition and their barrier properties against Cu diffusion. Vacuum 2016, 126, 10–15. [Google Scholar] [CrossRef]
  28. Chen, S.F.; Wang, S.J.; Yang, T.H.; Yang, Z.D.; Bor, H.Y.; Wei, C.N. Effect of nitrogen flow rate on TaN diffusion barrier layer deposited between a Cu layer and a Si-based substrate. Ceram. Int. 2017, 43, 12505–12510. [Google Scholar] [CrossRef]
  29. Kim, J.B.; Nandi, D.K.; Kim, T.H.; Jang, Y.; Bae, J.S.; Hong, T.E.; Kim, S.H. Atomic layer deposition of WNx thin films using a F-free tungsten metalorganic precursor and NH3 plasma as a Cu-diffusion barrier. Thin Solid Films 2019, 685, 393–401. [Google Scholar] [CrossRef]
  30. Suh, B.S.; Lee, Y.J.; Hwang, J.S.; Park, C.O. Properties of reactively sputtered WNx as Cu diffusion barrier. Thin Solid Films 1999, 348, 299–303. [Google Scholar] [CrossRef]
  31. Wojcik, H.; Kaltofen, R.; Merkel, U.; Krien, C.; Strehle, S.; Gluch, J.; Knaut, M.; Wenzel, C.; Preusse, A.; Bartha, J.W.; et al. Electrical Evaluation of Ru–W(–N), Ru–Ta(–N) and Ru–Mn films as Cu diffusion barriers. Microelectron. Eng. 2012, 92, 71–75. [Google Scholar] [CrossRef]
  32. Wang, Q.X.; Liang, S.H.; Wang, X.H.; Fan, Z.K. Diffusion barrier performance of amorphous W–Ti–N films in Cu metallization. Vacuum 2010, 84, 1270–1274. [Google Scholar]
  33. Lee, J.; Duh, J.G. Structural evolution of Zr–Cu–Ni–Al–N thin film metallic glass and its diffusion barrier performance in Cu-Si interconnect at elevated temperature. Vacuum 2017, 142, 81–86. [Google Scholar] [CrossRef]
  34. Hsiao, Y.T.; Tung, C.H.; Lin, S.J.; Yeh, J.W.; Chang, S.Y. Thermodynamic route for self-forming 1.5 nm V–Nb–Mo–Ta–W high-entropy alloy barrier layer: Roles of enthalpy and mixing entropy. Acta Mater. 2020, 199, 107–115. [Google Scholar] [CrossRef]
  35. Chang, J.C.; Tu, S.L.; Chen, M.C. Sputtered Cr and reactively sputtered CrNx serving as barrier layers against copper diffusion. J. Electrochem. Soc. 1998, 145, 4290–4296. [Google Scholar] [CrossRef]
  36. Marulanda, D.M.; Lousa, A.; Martinez-de-Olcoz, L.; Olaya, J.J. Microstructure characterization of nano-structured Cr/Cr2N multilayer films produced through radio frequency magnetron sputtering. Thin Solid Films 2014, 550, 272–277. [Google Scholar] [CrossRef]
  37. Lu, F.H.; Chen, H.Y. Phase changes of CrN films annealed at high temperature under controlled atmosphere. Thin Solid Films 2001, 398, 368–373. [Google Scholar] [CrossRef]
  38. Kouznetsov, V.; Macák, K.; Schneider, J.M.; Helmersson, U.; Petrov, I. A novel pulsed magnetron sputter technique utilizing very high target power densities. Surf. Coat. Technol. 1990, 122, 290–293. [Google Scholar] [CrossRef]
  39. Helmersson, U.; Lattemann, M.; Bohlmark, J.; Ehiasarian, A.P.; Gudmundsson, J.T. Ionized physical vapor deposition (IPVD): A review of technology and applications. Thin Solid Films 2006, 513, 1–24. [Google Scholar] [CrossRef] [Green Version]
  40. Gudmundsson, J.T.; Brenning, N.; Lundin, D.; Helmersson, U. High power impulse magnetron sputtering discharge. J. Vac. Sci. Technol. A Vac. Surf. Films 2012, 30, 030801. [Google Scholar] [CrossRef] [Green Version]
  41. Ehiasarian, A.P. High-power impulse magnetron sputtering and its applications. Pure Appl. Chem. 2010, 82, 1247–1258. [Google Scholar] [CrossRef]
  42. Sarakinos, K.; Alami, J.; Konstantinidis, S. High power pulsed magnetron sputtering: A review on scientific and engineering state of the art. Surf. Coat. Technol. 2010, 204, 1661–1684. [Google Scholar] [CrossRef]
  43. Purandare, Y.P.; Ehiasarian, A.P.; Hovsepian, P.E. Structure and properties of ZrN coatings deposited by high power impulse magnetron sputtering technology. J. Vac. Sci. Technol. A 2011, 29, 011004. [Google Scholar] [CrossRef]
  44. Ehiasarian, A.P.; Münz, W.-D.; Hultman, L.; Helmersson, U.; Petrov, I. High power pulsed magnetron sputtered CrNx films. Surf. Coat. Technol. 2003, 163, 267–272. [Google Scholar] [CrossRef]
  45. Chang, L.C.; Chang, C.Y.; You, Y.W. Ta–Zr–N thin films fabricated through HIPIMS/RFMS co-sputtering. Coatings 2017, 7, 189. [Google Scholar] [CrossRef]
  46. Chang, L.C.; Zheng, Y.Z.; Chen, Y.I. Mechanical properties of Zr–Si–N films fabricated through HiPIMS/RFMS co-sputtering. Coatings 2018, 8, 263. [Google Scholar] [CrossRef] [Green Version]
  47. Oliver, W.C.; Pharr, G.M. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res. 1992, 7, 1564–1583. [Google Scholar] [CrossRef]
  48. Janssen, G.C.A.M.; Abdalla, M.M.; van Keulen, F.; Pujada, B.R.; van Venrooy, B. Celebrating the 100th anniversary of the Stoney equation for film stress: Developments from polycrystalline steel strips to single crystal silicon wafers. Thin Solid Films 2009, 517, 1858–1867. [Google Scholar] [CrossRef]
  49. Barin, I. Thermochemical Data of Pure Substances, 3rd ed.; VCH: New York, NY, USA, 1995. [Google Scholar]
  50. Lin, J.; Sproul, W.D.; Moore, J.J.; Lee, S.; Myers, S. High rate deposition of thick CrN and Cr2N coatings using modulated pulse power (MPP) magnetron sputtering. Surf. Coat. Technol. 2011, 205, 3226–3234. [Google Scholar] [CrossRef]
  51. Bielawski, M. Residual stress control in TiN/Si coatings deposited by unbalanced magnetron sputtering. Surf. Coat. Technol. 2006, 200, 3987–3995. [Google Scholar] [CrossRef]
  52. Tan, S.; Zhang, X.; Wu, X.; Fang, F.; Jiang, J. Effect of substrate bias and temperature on magnetron sputtered CrSiN films. Appl. Surf. Sci. 2011, 257, 1850–1853. [Google Scholar] [CrossRef]
  53. Hirota, K.; Takano, Y.; Yoshinaka, M.; Yamaguchi, O. Hot isostatic pressing of chromium nitrides (Cr2N and CrN) prepared by self-propagating high-temperature synthesis. J. Am. Ceram. Soc. 2001, 84, 2120–2122. [Google Scholar] [CrossRef]
  54. Hones, P.; Sanjines, R.; Lévy, F. Characterization of sputter-deposited chromium nitride thin films for hard coatings. Surf. Coat. Technol. 1997, 94, 398–402. [Google Scholar] [CrossRef]
  55. Wei, G.; Rar, A.; Barnard, J.A. Composition, structure, and nanomechanical properties of DC-sputtered CrNx (0 ≤ x ≤ 1) thin films. Thin Solid Films 2001, 398, 460–464. [Google Scholar] [CrossRef]
  56. Pogrebnjak, A.D.; Beresnev, V.M.; Bondar, O.V.; Postolnyi, B.O.; Zaleski, K.; Coy, E.; Jurga, S.; Lisovenko, M.O.; Konarski, P.; Rebouta, L.; et al. Superhard CrN/MoN coatings with multilayer architecture. Mater. Des. 2018, 153, 47–59. [Google Scholar] [CrossRef]
  57. Tsui, T.Y.; Pharr, G.M.; Oliver, W.C.; Bhatia, C.S.; White, R.L.; Anders, S.; Anders, A.; Brown, I.G. Nanoindentation and nanoscratching of hard carbon coatings for magnetic disks. Mater. Res. Soc. Symp. Proc. 1995, 383, 447–452. [Google Scholar] [CrossRef] [Green Version]
  58. Li, H.; Liu, Z.; Li, J.; Huang, J.; Kong, J.; Wu, Q.; Xiong, D. Effects of Hf addition on the structure, mechanical and tribological properties of CrN film. Surf. Coat. Technol. 2020, 397, 126067. [Google Scholar] [CrossRef]
  59. Chen, X.; Du, Y.; Chung, Y.W. Commentary on using H/E and H3/E2 as proxies for fracture toughness of hard coatings. Thin Solid Films 2019, 688, 137265. [Google Scholar] [CrossRef]
  60. Odén, M.; Ericsson, C.; Håkansson, G.; Ljungcrantz, H. Microstructure and mechanical behavior of arc-evaporated Cr–N coatings. Surf. Coat. Technol. 1999, 114, 39–51. [Google Scholar] [CrossRef]
  61. Meng, Y.; Song, Z.X.; Li, Y.H.; Qian, D.; Hu, W.; Xu, K.W. Thermal stability of ultra thin Zr–B-–N films as diffusion barrier between Cu and Si. Appl. Surf. Sci. 2020, 527, 146810. [Google Scholar] [CrossRef]
  62. Zalar, A.; Hofmann, S.; Panjan, P. Characterization of chemical interdiffusivities at silicon/metal interfaces in initial reaction stages. Vacuum 1997, 48, 625–627. [Google Scholar] [CrossRef]
Coatings 11 00690 g001 550
Figure 1. GIXRD patterns of (a) Cr65W4N31, (b) Cr62W3N35, (c) Cr58W2N40, and (d) Cr51W2N47 coatings.
Figure 1. GIXRD patterns of (a) Cr65W4N31, (b) Cr62W3N35, (c) Cr58W2N40, and (d) Cr51W2N47 coatings.
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Figure 2. Cross-sectional FE-SEM images of (a) Cr65W4N31, (b) Cr62W3N35, (c) Cr58W2N40, and (d) Cr51W2N47 coatings.
Figure 2. Cross-sectional FE-SEM images of (a) Cr65W4N31, (b) Cr62W3N35, (c) Cr58W2N40, and (d) Cr51W2N47 coatings.
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Figure 3. (a) XTEM and (b) HRTEM images of the Cr51W2N47 coatings.
Figure 3. (a) XTEM and (b) HRTEM images of the Cr51W2N47 coatings.
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Figure 4. Surface roughness values of the CrWN coatings.
Figure 4. Surface roughness values of the CrWN coatings.
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Figure 5. H and E levels of CrWN coatings.
Figure 5. H and E levels of CrWN coatings.
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Figure 6. Residual stresses of CrWN coatings.
Figure 6. Residual stresses of CrWN coatings.
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Figure 7. Relationship between (a) hardness and H3/E2 levels and (b) Young’s modulus against residual stresses of the CrWN coatings.
Figure 7. Relationship between (a) hardness and H3/E2 levels and (b) Young’s modulus against residual stresses of the CrWN coatings.
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Figure 8. H/E and H3/E2 ratios of CrWN coatings.
Figure 8. H/E and H3/E2 ratios of CrWN coatings.
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Figure 9. Wear scars and elemental mapping of (a) Cr65W4N31, (b) Cr62W3N35, (c) Cr58W2N40, and (d) Cr51W2N47 coatings.
Figure 9. Wear scars and elemental mapping of (a) Cr65W4N31, (b) Cr62W3N35, (c) Cr58W2N40, and (d) Cr51W2N47 coatings.
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Figure 10. Scratch scars of the CrWN coatings.
Figure 10. Scratch scars of the CrWN coatings.
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Figure 11. Sheet resistance of the annealed Cu/CrWN/Cr/Si samples.
Figure 11. Sheet resistance of the annealed Cu/CrWN/Cr/Si samples.
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Figure 12. GIXRD patterns of (a) as-deposited and (b–d) annealed Cu/Cr59W2N39/Cr/Si samples.
Figure 12. GIXRD patterns of (a) as-deposited and (b–d) annealed Cu/Cr59W2N39/Cr/Si samples.
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Figure 13. GIXRD patterns of (a) as-deposited and (b–d) annealed Cu/Cr54W6N40/Cr/Si samples.
Figure 13. GIXRD patterns of (a) as-deposited and (b–d) annealed Cu/Cr54W6N40/Cr/Si samples.
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Figure 14. AES depth profiles of (a) as-deposited, (b) 600 °C, and (c) 650 °C annealed Cu/Cr59W2N39/Cr/Si samples. (Annealed in vacuum for 1 h).
Figure 14. AES depth profiles of (a) as-deposited, (b) 600 °C, and (c) 650 °C annealed Cu/Cr59W2N39/Cr/Si samples. (Annealed in vacuum for 1 h).
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Figure 15. AES depth profiles of (a) as-deposited, (b) 600 °C, and (c) 650 °C annealed Cu/Cr54W6N40/Cr/Si samples. (Annealed in vacuum for 1 h).
Figure 15. AES depth profiles of (a) as-deposited, (b) 600 °C, and (c) 650 °C annealed Cu/Cr54W6N40/Cr/Si samples. (Annealed in vacuum for 1 h).
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Table
Table 1. Co-sputtering parameters, atomic compositions, and thicknesses of CrWN coatings.
Table 1. Co-sputtering parameters, atomic compositions, and thicknesses of CrWN coatings.
SampleN2 FlowfN2 1Atomic Compositions (at.%)ThicknessRate
(sccm)CrWNO(nm)(nm/min)
Cr65W4N3130.164.7 ± 0.64.0 ± 0.031.0 ± 0.60.3 ± 0.195412.1
Cr62W3N3560.261.9 ± 0.52.8 ± 0.135.0 ± 0.40.3 ± 0.2118014.6
Cr58W2N4090.358.1 ± 0.82.2 ± 0.139.4 ± 0.70.3 ± 0.194711.4
Cr51W2N47120.450.6 ± 0.62.0 ± 0.646.9 ± 0.50.3 ± 0.093310.9
1fN2: nitrogen flow ratio.
Table
Table 2. Co-sputtering parameters, atomic compositions, and thicknesses of CrWN films.
Table 2. Co-sputtering parameters, atomic compositions, and thicknesses of CrWN films.
SampleWCr 1WW 2fN2Atomic Compositions (at.%)Thickness
(W)(W)CrWNO(nm)
Cr59W2N39500500.457.5 ± 0.52.3 ± 0.037.8 ± 0.52.4 ± 0.0108
Cr54W6N405001000.452.8 ± 0.56.5 ± 0.239.1 ± 0.81.6 ± 0.2103
1WCr: power on Cr target; 2 WW: power on W target.
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Chang, L.-C.; Wu, C.-E.; Ou, T.-Y. Mechanical Properties and Diffusion Barrier Performance of CrWN Coatings Fabricated through Hybrid HiPIMS/RFMS. Coatings 2021, 11, 690. https://doi.org/10.3390/coatings11060690

AMA Style

Chang L-C, Wu C-E, Ou T-Y. Mechanical Properties and Diffusion Barrier Performance of CrWN Coatings Fabricated through Hybrid HiPIMS/RFMS. Coatings. 2021; 11(6):690. https://doi.org/10.3390/coatings11060690

Chicago/Turabian Style

Chang, Li-Chun, Cheng-En Wu, and Tzu-Yu Ou. 2021. "Mechanical Properties and Diffusion Barrier Performance of CrWN Coatings Fabricated through Hybrid HiPIMS/RFMS" Coatings 11, no. 6: 690. https://doi.org/10.3390/coatings11060690

APA Style

Chang, L. -C., Wu, C. -E., & Ou, T. -Y. (2021). Mechanical Properties and Diffusion Barrier Performance of CrWN Coatings Fabricated through Hybrid HiPIMS/RFMS. Coatings, 11(6), 690. https://doi.org/10.3390/coatings11060690

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