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Structural and Electrical Characterizations of CuNi Thin Film Resistors
Available online at www.sciencedirect.com
ScienceDirect Procedia Chemistry 19 (2016) 619 – 625
5th International Conference on Recent Advances in Materials, Minerals and Environment (RAMM) & 2nd International Postgraduate Conference on Materials, Mineral and Polymer (MAMIP), 4-6 August 2015
Structural and Electrical Characterizations of CuNi Thin Film Resistors Nurul Khalidah Yusopa, Nurulakmal Mohd Shariffb , See Chin Chowc, Ahmad Badri Ismail a,b a
School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia,14300 Nibong Tebal, Pulau Pinang, Malaysia b School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia,14300 Nibong Tebal, Pulau Pinang, Malaysia
Abstract This work studied the development of Cu-Ni for thin film resistor; specifically reported in this paper is the surface morphology and resistance. Films were deposited on the substrate of commercialized flame retardant (generally known as FR4) printed circuit board by using thermal evaporator. The thickness of the film was set to 100 nm and the dc current was maintained at 26 A. The sheet resistance and bulk resistivity of the thin films were measured via four-point probe test. The stability of thin film resistor was measured through temperature coefficient of resistance (TCR). According to the experimental results, it can be seen that the sheet resistance of the thin film resistor decreased with increasing copper composition. © Published by Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license ©2016 2016The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia. Peer-review under responsibility of School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia Keywords:CuNi thin film, four-point probes test, thin film resistor
* Corresponding author. Tel.: +6012 - 5210544 E-mail address:[email protected]
1. Introduction Thin films technology in the electronic industries especially as resistor are developing very fast since they have potential applications in computers, smartphones, tablets and other electronic devices 1–7. Copper nickel (Cu-Ni), an alloy made up between copper and nickel either physically mixing or chemically mixing to form homogeneous solid solution7,8, is one of the material that is commercially used in fabrication of resistor since it is cheaper compared toother materials such as nickel chromium. Different sizes, shapes and composition of Cu-Ni alloys contribute to
1876-6196 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia doi:10.1016/j.proche.2016.03.061
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Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
different properties however Cu-Ni alloys generally have low resistivity and low temperature coefficient of resistance (TCR) which are guaranteed to provide low and constant resistance over a temperature range 7,9. These properties are required in microelectronic industries to improve batteries consumption. The most common copper alloy used in resistor is known as ‘constantan’ which is Cu alloyed with 45% Ni with low resistivity less than 50 μΩ.cm and extremely low temperature coefficient resistance (TCR) value less than 50 x 10 -6 /K. There are a lot of techniques have been used in order to form Cu-Ni alloys such as mechanical alloying7,9, sol gel method10 and electrochemical process11. In this current work, we prepared Cu-Ni thin film resistor by using evaporation process and examined the surface morphology, and the dependence of electrical properties such as resistivity and TCR. 2. Methodology A mixture of copper and nickel with appropriate composition were mixed according to the intended weight percentage. The alloy was milled for 3 hours using zirconia ball with ratio 1:10 of powder to ball before it was then palletized using pressing method. The pallet was used as the target source in evaporation technique using EMITECH K950X Turbo Evaporator. A 3.5 mm x 3.5 mm printed circuit board was used as the substrate in the deposition process. In order to see the effect of composition on the thin film resistor, the composition of copper was set to 50 wt. %, 60 wt. %, 70 wt. % and 80 wt. % of Cu. The electrical properties of the film such as sheet resistance and bulk resistivity were analyzed using JANDELL Cylindrical four-point probes with the samples were divided into 9 sites. In order to examine the stability of film against temperature, a set of TCR experiment was set up using the Wheatstone bridge theory as shown in Figure 1. The value of TCR can be obtained from the slope of temperature against resistance. Scanning electron microscope (SEM) model S-36; Leica Cambridge Ltd. with a Leo Supra 35VP system and X-ray fluorescence (XRF) were used for material characterization and verification including verification of samples composition, surface morphology and thickness cross section. Phase analysis was carried out using XRD (Philip PW 1820) to confirm the presence of Cu-Ni coated film after sputtering method with the addition of Xpert Highscore Software.
Fig. 1. Circuit used as TCR test
3. Results and Discussion
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
621
From four-point probes testing the results showed that the sheet resistance decreased as the composition of copper in the alloy was increased (see Table 1). The film resistance of Cu-Ni alloy coatings also decreased with increasing Cu content of the coatings. The resistivity values of thin film was plotted against Cu composition and presented in Figure 2. The trend is as expected as higher amount of Cu, which has higher electrical conductivity than Ni, would increase the conductivity of thin film. The results of sheet resistance obtained as in Table 1 with 9 sites were measured on each samples. Overall all the sheet resistances recorded were much lower in values due to the films surfaces as shown in Figure 4; which can carry more current for application purpose as reported by Hur and coworkers9. Other factors such as the effect of substrate condition prior to the deposition highly influence the sheet resistance as such reported by Yang and fellow researchers12. All films showed a small gradient increased of resistance in TCR test as shown in Figure 3. The resistance of the thin film changed as the temperature was increased and reverts to the original values once the power supply was turned off. This indicates that the films experienced thermal expansion that usually happened in copper alloyas reposted by researcher6 but due to the small changes the resistors stability are good up to temperature 100 0C. Table 1. Electrical properties of different copper compositions. Copper content (%)
Sheet resistance(Ω/sq)
Bulk Resistance (Ω)
50
5.7075
51.37
60
4.3086
38.78
70
3.8344
32.19
80
1.8465
16.62
Resistivity x10-7 (Ω.cm)
7 6 5 4 3 2 1 0 0
20
40 60 80 Cu composition (wt. %)
100
Fig. 2. Resistivity values as a function to 50 wt. %, 60 wt. %, 70 wt. % and 80 wt. % of copper composition
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Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
1.1
0.035
0.03
1
0.025
0.02 0.8 0.015
R//Ro
TCR (oC-1)
0.9
0.7 0.01 0.6
0.005
0
0.5 40
45
50
55
60
65
70
75
80
85
Cu (wt. %) Fig. 3. The variation of TCR and R/R0 as a function of copper composition
Images obtained from the analysis by SEM for thin films with respective composition of copper produced by evaporation method are shown in Figure 4 (a), (b), (c) and (d). Thin film produced using thermal evaporation method has a rough and porous surface. The surfaces displayed beehives-like deposits which contributed to the low values of sheet resistance since the roughness of morphology increased 9. As tabulated in Table 2 all the samples were successfully deposited on substrate with their respective thicknesses.
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
(a)
(b)
(c)
(d)
Figure 4: Morphologies of CuNi alloys at a different composition (a) 50 wt. % at magnification x500 (b) 60 wt. % at magnification x500 (c) 70 wt. % at magnification x1000 and (d) 80 wt. % at magnification x500 Table 2. Thickness of coating achieved by sputtering method Copper composition (wt. %)
Thickness achieved (nm)
50
102.0
60
126.8
70
115.3
80
102.9
Figure 5 presents the XRD patterns for the Cu-Ni samples with different copper compositions. XRD analysis revealed all samples exhibited the cubic structure from the two planes of (111) and (200) of Cu-Ni9–11,13 There are no impurity peaks detected in all the samples as only two peaks existed. It is noticed that the planes reflection shift towards the lower angles as the Cu content increased similarly reported by Wu and colleques 11. It was assumed due to the composition of the copper hence changes the lattice occupy by Cu and Ni causing sample with higher copper content to small shrinkage. The lattice constant (a) obtained from the interplanar spacing (d) value corresponding to (111) plane is 0.8 A which is lower than the actual lattice constant of Cu and Ni hence contributed to the lower reading in sheet resistance. Verification of element composition that existed in the samples by EDX testing was done and the amount of each element was tabulated in Table 3 according to their respective weight percentages and atomic percentages.
623
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Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
(111) CuNi (200) Intensity (counts)
Cu80Ni20
Cu70Ni30
Cu60Ni40
Cu50Ni50 30
35
40
45
50
55
2ϴ (degrees) Fig. 5. XRD patterns for the CuNi samples deposited by different Cu compositions
Table 3: Parameters for EDX testing according to copper composition Copper Composition (%)
Cu
Ni
Weight percentages (%)
Atomic percentages (%)
Weight percentages (%)
Atomic percentages (%)
50
70.20
68.52
29.80
31.48
60
65.20
62.30
34.80
37.70
70
74.61
73.09
25.39
26.91
80
81.41
80.19
18.59
19.81
4. Conclusion CuNi thin films were successfully deposited using thermal evaporator obtaining thickness of 102 – 126.8 nm with minimal impurities. The composition remains in the range of its original composition upon deposited using thermal evaporation method. The Cu content controlled the electrical properties of the resistors. Deposited CuNi thin film deposited on the FR4 substrate produced a beehive-like structure with the sheet resistance range between 1 – 6 Ω/sq and recorded the highest resistance of 50 Ω.
References
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
625
1. Birkett M, Penlington R, Wan C, Zoppi G. Structural and electrical properties of CuAlMo thin films prepared by magnetron sputtering. ThiSolid Films. 2013;540(0):235-241. doi:http://dx.doi.org/10.1016/j.tsf.2013.05.145. 2. Kang SM, Yoon SG, Suh SJ, Yoon DH. Control of electrical resistivity of TaN thin films by reactive sputtering for embedded passive resistors. Thin Solid Films. 2008;516:3568-3571. doi:10.1016/j.tsf.2007.08.027. 3. Xu G, Li Y, Huang QA, Li W. In-line method for extracting the temperature coefficient of resistance of surface-micromachined polysilicon thin films. Sensors Actuators, A Phys. 2007;136:249-254. doi:10.1016/j.sna.2006.10.033. 4. Shkir M, Abbas H, Siddhartha, Khan ZR. Effect of thickness on the structural, optical and electrical properties of thermally evaporated PbI2 thin films. J Phys Chem Solids. 2012;73(11):1309-1313. doi:10.1016/j.jpcs.2012.04.019. 5. Chen H-L, Lu Y-M, Hwang W-S. Effect of Film Thickness on Structural and Electrical Properties of Sputter-Deposited Nickel Oxide Films. Mater Trans. 2005;46(4):872-879. doi:10.2320/matertrans.46.872. 6. Wang J, Clouser S. Thin Film Embedded Resistors. Gould Electron Inc, 34929 Curtis Blvd, Ohio 44095. 2013. 7. Ishikawa M, Enomoto H, Mikamoto N, Nakamura T, Matsuoka M, Iwakura C. Preparation of thin film resistors with low resistivity and low TCR by heat treatment of multilayered Cu/Ni deposits. Surf Coatings Technol. 1998;110(3):121-127. doi:http://dx.doi.org/10.1016/S02578972(98)00682-3. 8. De León-Quiroz EL, Puente-Urbina B a., Vázquez-Obregón D, García-Cerda L a. Preparation and structural characterization of CuNi nanoalloys obtained by polymeric precursor method. Mater Lett. 2013;91:67-70. doi:10.1016/j.matlet.2012.09.063. 9. Hur S-G, Kim D-J, Kang B-D, Yoon S-G. The Structural and Electrical Properties of CuNi Thin-Film Resistors Grown on AlN Substrates for Π-Type Attenuator Application. J Electrochem Soc. 2005;152:G472. doi:10.1149/1.1901675. 10. De Leon-Quiroz EL, Vazquez Obregon D, Ponce Pedraza A, Jose-Yacaman M, Garcia-Cerda LA. Synthesis of Magnetic CuNi Nanoalloys by Sol-Gel-Based Pechini Method. Magn IEEE Trans. 2013;49(8):4522-4524. doi:10.1109/tmag.2013.2259225. 11. Wu H, Wang Y, Zhong Q, Sheng M, Du H, Li Z. The semi-conductor property and corrosion resistance of passive film on electroplated Ni and Cu–Ni alloys. J Electroanal Chem. 2011;663(2):59-66. doi:http://dx.doi.org/10.1016/j.jelechem.2011.09.013. 12. Yang J, Miller P, Radulescu F, et al. Low Energy Sputter Deposition and Properties of NiCr Thin Film Resistors for GaAs Integrated Circuits. CS MANTECH. 2005. 13.http://www.researchgate.net/publication/229021564_Low_Energy_Sputter_Deposition_and_Properties_of_NiCr_Thin_Film_Resistors_for_G aAs_Integrated_Circuits. Accessed February 20, 2015. 14. Varea A, Pellicer E, Pané S, et al. Mechanical properties and corrosion behaviour of nanostructured Cu-rich CuNi electrodeposited films. Int J Electrochem Sci. 2012;7:1288-1302.
ScienceDirect Procedia Chemistry 19 (2016) 619 – 625
5th International Conference on Recent Advances in Materials, Minerals and Environment (RAMM) & 2nd International Postgraduate Conference on Materials, Mineral and Polymer (MAMIP), 4-6 August 2015
Structural and Electrical Characterizations of CuNi Thin Film Resistors Nurul Khalidah Yusopa, Nurulakmal Mohd Shariffb , See Chin Chowc, Ahmad Badri Ismail a,b a
School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia,14300 Nibong Tebal, Pulau Pinang, Malaysia b School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia,14300 Nibong Tebal, Pulau Pinang, Malaysia
Abstract This work studied the development of Cu-Ni for thin film resistor; specifically reported in this paper is the surface morphology and resistance. Films were deposited on the substrate of commercialized flame retardant (generally known as FR4) printed circuit board by using thermal evaporator. The thickness of the film was set to 100 nm and the dc current was maintained at 26 A. The sheet resistance and bulk resistivity of the thin films were measured via four-point probe test. The stability of thin film resistor was measured through temperature coefficient of resistance (TCR). According to the experimental results, it can be seen that the sheet resistance of the thin film resistor decreased with increasing copper composition. © Published by Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license ©2016 2016The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia. Peer-review under responsibility of School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia Keywords:CuNi thin film, four-point probes test, thin film resistor
* Corresponding author. Tel.: +6012 - 5210544 E-mail address:[email protected]
1. Introduction Thin films technology in the electronic industries especially as resistor are developing very fast since they have potential applications in computers, smartphones, tablets and other electronic devices 1–7. Copper nickel (Cu-Ni), an alloy made up between copper and nickel either physically mixing or chemically mixing to form homogeneous solid solution7,8, is one of the material that is commercially used in fabrication of resistor since it is cheaper compared toother materials such as nickel chromium. Different sizes, shapes and composition of Cu-Ni alloys contribute to
1876-6196 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia doi:10.1016/j.proche.2016.03.061
620
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
different properties however Cu-Ni alloys generally have low resistivity and low temperature coefficient of resistance (TCR) which are guaranteed to provide low and constant resistance over a temperature range 7,9. These properties are required in microelectronic industries to improve batteries consumption. The most common copper alloy used in resistor is known as ‘constantan’ which is Cu alloyed with 45% Ni with low resistivity less than 50 μΩ.cm and extremely low temperature coefficient resistance (TCR) value less than 50 x 10 -6 /K. There are a lot of techniques have been used in order to form Cu-Ni alloys such as mechanical alloying7,9, sol gel method10 and electrochemical process11. In this current work, we prepared Cu-Ni thin film resistor by using evaporation process and examined the surface morphology, and the dependence of electrical properties such as resistivity and TCR. 2. Methodology A mixture of copper and nickel with appropriate composition were mixed according to the intended weight percentage. The alloy was milled for 3 hours using zirconia ball with ratio 1:10 of powder to ball before it was then palletized using pressing method. The pallet was used as the target source in evaporation technique using EMITECH K950X Turbo Evaporator. A 3.5 mm x 3.5 mm printed circuit board was used as the substrate in the deposition process. In order to see the effect of composition on the thin film resistor, the composition of copper was set to 50 wt. %, 60 wt. %, 70 wt. % and 80 wt. % of Cu. The electrical properties of the film such as sheet resistance and bulk resistivity were analyzed using JANDELL Cylindrical four-point probes with the samples were divided into 9 sites. In order to examine the stability of film against temperature, a set of TCR experiment was set up using the Wheatstone bridge theory as shown in Figure 1. The value of TCR can be obtained from the slope of temperature against resistance. Scanning electron microscope (SEM) model S-36; Leica Cambridge Ltd. with a Leo Supra 35VP system and X-ray fluorescence (XRF) were used for material characterization and verification including verification of samples composition, surface morphology and thickness cross section. Phase analysis was carried out using XRD (Philip PW 1820) to confirm the presence of Cu-Ni coated film after sputtering method with the addition of Xpert Highscore Software.
Fig. 1. Circuit used as TCR test
3. Results and Discussion
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
621
From four-point probes testing the results showed that the sheet resistance decreased as the composition of copper in the alloy was increased (see Table 1). The film resistance of Cu-Ni alloy coatings also decreased with increasing Cu content of the coatings. The resistivity values of thin film was plotted against Cu composition and presented in Figure 2. The trend is as expected as higher amount of Cu, which has higher electrical conductivity than Ni, would increase the conductivity of thin film. The results of sheet resistance obtained as in Table 1 with 9 sites were measured on each samples. Overall all the sheet resistances recorded were much lower in values due to the films surfaces as shown in Figure 4; which can carry more current for application purpose as reported by Hur and coworkers9. Other factors such as the effect of substrate condition prior to the deposition highly influence the sheet resistance as such reported by Yang and fellow researchers12. All films showed a small gradient increased of resistance in TCR test as shown in Figure 3. The resistance of the thin film changed as the temperature was increased and reverts to the original values once the power supply was turned off. This indicates that the films experienced thermal expansion that usually happened in copper alloyas reposted by researcher6 but due to the small changes the resistors stability are good up to temperature 100 0C. Table 1. Electrical properties of different copper compositions. Copper content (%)
Sheet resistance(Ω/sq)
Bulk Resistance (Ω)
50
5.7075
51.37
60
4.3086
38.78
70
3.8344
32.19
80
1.8465
16.62
Resistivity x10-7 (Ω.cm)
7 6 5 4 3 2 1 0 0
20
40 60 80 Cu composition (wt. %)
100
Fig. 2. Resistivity values as a function to 50 wt. %, 60 wt. %, 70 wt. % and 80 wt. % of copper composition
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Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
1.1
0.035
0.03
1
0.025
0.02 0.8 0.015
R//Ro
TCR (oC-1)
0.9
0.7 0.01 0.6
0.005
0
0.5 40
45
50
55
60
65
70
75
80
85
Cu (wt. %) Fig. 3. The variation of TCR and R/R0 as a function of copper composition
Images obtained from the analysis by SEM for thin films with respective composition of copper produced by evaporation method are shown in Figure 4 (a), (b), (c) and (d). Thin film produced using thermal evaporation method has a rough and porous surface. The surfaces displayed beehives-like deposits which contributed to the low values of sheet resistance since the roughness of morphology increased 9. As tabulated in Table 2 all the samples were successfully deposited on substrate with their respective thicknesses.
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
(a)
(b)
(c)
(d)
Figure 4: Morphologies of CuNi alloys at a different composition (a) 50 wt. % at magnification x500 (b) 60 wt. % at magnification x500 (c) 70 wt. % at magnification x1000 and (d) 80 wt. % at magnification x500 Table 2. Thickness of coating achieved by sputtering method Copper composition (wt. %)
Thickness achieved (nm)
50
102.0
60
126.8
70
115.3
80
102.9
Figure 5 presents the XRD patterns for the Cu-Ni samples with different copper compositions. XRD analysis revealed all samples exhibited the cubic structure from the two planes of (111) and (200) of Cu-Ni9–11,13 There are no impurity peaks detected in all the samples as only two peaks existed. It is noticed that the planes reflection shift towards the lower angles as the Cu content increased similarly reported by Wu and colleques 11. It was assumed due to the composition of the copper hence changes the lattice occupy by Cu and Ni causing sample with higher copper content to small shrinkage. The lattice constant (a) obtained from the interplanar spacing (d) value corresponding to (111) plane is 0.8 A which is lower than the actual lattice constant of Cu and Ni hence contributed to the lower reading in sheet resistance. Verification of element composition that existed in the samples by EDX testing was done and the amount of each element was tabulated in Table 3 according to their respective weight percentages and atomic percentages.
623
624
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
(111) CuNi (200) Intensity (counts)
Cu80Ni20
Cu70Ni30
Cu60Ni40
Cu50Ni50 30
35
40
45
50
55
2ϴ (degrees) Fig. 5. XRD patterns for the CuNi samples deposited by different Cu compositions
Table 3: Parameters for EDX testing according to copper composition Copper Composition (%)
Cu
Ni
Weight percentages (%)
Atomic percentages (%)
Weight percentages (%)
Atomic percentages (%)
50
70.20
68.52
29.80
31.48
60
65.20
62.30
34.80
37.70
70
74.61
73.09
25.39
26.91
80
81.41
80.19
18.59
19.81
4. Conclusion CuNi thin films were successfully deposited using thermal evaporator obtaining thickness of 102 – 126.8 nm with minimal impurities. The composition remains in the range of its original composition upon deposited using thermal evaporation method. The Cu content controlled the electrical properties of the resistors. Deposited CuNi thin film deposited on the FR4 substrate produced a beehive-like structure with the sheet resistance range between 1 – 6 Ω/sq and recorded the highest resistance of 50 Ω.
References
Nurul Khalidah Yusop et al. / Procedia Chemistry 19 (2016) 619 – 625
625
1. Birkett M, Penlington R, Wan C, Zoppi G. Structural and electrical properties of CuAlMo thin films prepared by magnetron sputtering. ThiSolid Films. 2013;540(0):235-241. doi:http://dx.doi.org/10.1016/j.tsf.2013.05.145. 2. Kang SM, Yoon SG, Suh SJ, Yoon DH. Control of electrical resistivity of TaN thin films by reactive sputtering for embedded passive resistors. Thin Solid Films. 2008;516:3568-3571. doi:10.1016/j.tsf.2007.08.027. 3. Xu G, Li Y, Huang QA, Li W. In-line method for extracting the temperature coefficient of resistance of surface-micromachined polysilicon thin films. Sensors Actuators, A Phys. 2007;136:249-254. doi:10.1016/j.sna.2006.10.033. 4. Shkir M, Abbas H, Siddhartha, Khan ZR. Effect of thickness on the structural, optical and electrical properties of thermally evaporated PbI2 thin films. J Phys Chem Solids. 2012;73(11):1309-1313. doi:10.1016/j.jpcs.2012.04.019. 5. Chen H-L, Lu Y-M, Hwang W-S. Effect of Film Thickness on Structural and Electrical Properties of Sputter-Deposited Nickel Oxide Films. Mater Trans. 2005;46(4):872-879. doi:10.2320/matertrans.46.872. 6. Wang J, Clouser S. Thin Film Embedded Resistors. Gould Electron Inc, 34929 Curtis Blvd, Ohio 44095. 2013. 7. Ishikawa M, Enomoto H, Mikamoto N, Nakamura T, Matsuoka M, Iwakura C. Preparation of thin film resistors with low resistivity and low TCR by heat treatment of multilayered Cu/Ni deposits. Surf Coatings Technol. 1998;110(3):121-127. doi:http://dx.doi.org/10.1016/S02578972(98)00682-3. 8. De León-Quiroz EL, Puente-Urbina B a., Vázquez-Obregón D, García-Cerda L a. Preparation and structural characterization of CuNi nanoalloys obtained by polymeric precursor method. Mater Lett. 2013;91:67-70. doi:10.1016/j.matlet.2012.09.063. 9. Hur S-G, Kim D-J, Kang B-D, Yoon S-G. The Structural and Electrical Properties of CuNi Thin-Film Resistors Grown on AlN Substrates for Π-Type Attenuator Application. J Electrochem Soc. 2005;152:G472. doi:10.1149/1.1901675. 10. De Leon-Quiroz EL, Vazquez Obregon D, Ponce Pedraza A, Jose-Yacaman M, Garcia-Cerda LA. Synthesis of Magnetic CuNi Nanoalloys by Sol-Gel-Based Pechini Method. Magn IEEE Trans. 2013;49(8):4522-4524. doi:10.1109/tmag.2013.2259225. 11. Wu H, Wang Y, Zhong Q, Sheng M, Du H, Li Z. The semi-conductor property and corrosion resistance of passive film on electroplated Ni and Cu–Ni alloys. J Electroanal Chem. 2011;663(2):59-66. doi:http://dx.doi.org/10.1016/j.jelechem.2011.09.013. 12. Yang J, Miller P, Radulescu F, et al. Low Energy Sputter Deposition and Properties of NiCr Thin Film Resistors for GaAs Integrated Circuits. CS MANTECH. 2005. 13.http://www.researchgate.net/publication/229021564_Low_Energy_Sputter_Deposition_and_Properties_of_NiCr_Thin_Film_Resistors_for_G aAs_Integrated_Circuits. Accessed February 20, 2015. 14. Varea A, Pellicer E, Pané S, et al. Mechanical properties and corrosion behaviour of nanostructured Cu-rich CuNi electrodeposited films. Int J Electrochem Sci. 2012;7:1288-1302.