332
Langmuir 2006, 22, 332-337
Micropatterning of Copper on a Poly(ethylene terephthalate) Substrate Modified with a Self-Assembled Monolayer Susumu Sawada, Yoshitake Masuda,* Peixin Zhu, and Kunihito Koumoto Nagoya UniVersity, Graduate School of Engineering, Nagoya 464-8603, Japan ReceiVed June 9, 2005. In Final Form: October 25, 2005 We have developed a technique for the site-selective electroless deposition of Cu on poly(ethylene terephthalate) (PET) substrate modified with an organic self-assembled monolayer (SAM). The PET substrate was first modified with a silica-like layer by being dip-coated in an acetone solution of 3-aminopropyltrimethoxysilane and treated with UV light. The PET substrate was further modified with thiol groups using a 3-mercaptopropyltrimethoxysilane-SAM and then irradiated by UV light through a photomask to prepare thiol-group regions and OH-group regions. Cu was then deposited on only the thiol-group regions of the substrate by electroless deposition in a neutral solution with no catalysts by using dimethylamineborane as a reducing reagent. This site-selective deposition process can control the deposition conditions by an organic thin film fabricated on a surface-modified PET substrate, and thus can be applied to other low heat-resistant substrates.
Introduction Metallic copper films have attracted much attention for developing microcircuits for ultralarge scale integration (ULSI) devices instead of aluminum metallization1 because of their high electromigration and superior electrical conductivity.2-4 Recently, Cu films, especially on polymer substrates such as poly(ethylene terephthalate) (PET) and polyimide (PI), have become very important for such applications as ULSI, multichip module (MCM) packing, flexible printed circuit (FPC) boards, and electromagnetic interference (EMI) shielding film for plasma display panels (PDP).5,6 There have been many reports on copper metallization techniques, including sputtering and chemical vapor deposition (CVD). However, these methods require high-temperature treatment, which is not appropriate for polymer substrates. Electroless deposition of Cu has the significant merit of lower cost than these methods, fast deposition, and formation of good membranes at low temperature. In addition, Cu is suitable for wet processes since its oxidation-reduction potential (ORP) is electropositive. The method of fabricating a pattern of Cu film is very important in ULSI. Techniques such as etching have been developed and are now used in the microelectronics industry, but the patterning processes based on the etching of Cu involve many processing steps, including coating of the resist, photolithography, metal deposition, and etching. Additionally, there is a growing need for sophisticated patterning techniques for functional materials on polymer films to fabricate flexible devices. PET is widely used in various forms for an enormous range of applications because of its excellent mechanical and chemical properties, such as mechanical strength, toughness, fatigue resistance at elevated temperatures, and a high crystalline melting temperature. * To whom correspondence should be addressed. Tel: +81-52-789-3329; fax: +81-52-789-3201; e-mail:
[email protected]. (1) Andricacos, P. C.; Uzoh, C.; Dukovic, J. O.; Horkans, J.; Deligianni, H. IBM J. Res. DeV. 1998, 42, 567. (2) Matienzo, L. J.; Unertl, W. N. In Polyimides: Fundamentals and Applications; Ghosh, M. K., Mittal, K. L., Eds.; Dekker: New York, 1996; p 629. (3) Jair, A.; Kodas, T. T.; Jairath, R.; Hampden-Smith, M. J. J. Vac. Sci. Technol. 1993, 11, 2107. (4) Cho, N. I.; Park, D. I. Thin Solid Films 1997, 308, 465. (5) Ikeda, S.; Akamatsu, K.; Nawahune, H. J. Mater. Chem. 2001, 11, 2919. (6) Oh, K. W.; Kim, D. J.; Kim, S. H. J. Appl. Polym. Sci. 2002, 84, 1369.
However, its intrinsic low surface energy results in poor adhesion, wettability, and biocompatibility.8 Therefore, there are few reports on Cu patterning on PET substrates because of the lack of reactivity between Cu and PET substrates. To overcome these problems, we have developed a technique of site-selective electroless deposition of Cu on a PET substrate modified with an organic self-assembled monolayer (SAM). Siteselective deposition of Cu thin films can be realized on either flexible or rigid substrates in an aqueous solution at low temperature. This process can reduce the number of steps and control the adsorption of Cu by utilizing interactions between the Cu surfaces and the modified PET substrate. The interfacial interactions could improve the deposition conditions, such as deposition rate and site-selectivity, and the thin film properties, such as adhesion, surface morphology, and electrical conductivity. SAMs have many applications since they are capable of controlling the physicochemical surface properties.9 In particular, micro- and nanopatterned SAMs have attracted increasing interest for electronic, photonic, and biological device fabrication because the possibility of metal deposition or adsorption on only the desired area has been demonstrated.10 We have succeeded in micropatterning ceramic thin films in aqueous solutions, such as TiO2,11,12 SnO2,13 ZnO,14 ZrO2,15 Ta2O5,16 SrTiO3,17 and Fe3O4,18 on silicon wafers using SAMs as templates. We also reported the micropatterning of Cu thin film on a silicon wafer by electroless deposition without using a catalyst such as Pd that (7) Schlesinger, M.; Paunovic, M. Modern Electroplating, 4th ed., Wiley: New York, 2000. (8) Chen, W.; McCarthy, T. J. Macromolecules 1998, 31, 11, 3648. (9) Ulman, A. Chem. ReV. 1996, 96, 1533. (10) Dulcey, C. S.; Georger, J. H.; Krauthamer, V.; Stenger, D. A.; Fare, T. L.; Calvert, J. M. Science 1991, 252, 551. (11) Masuda, Y.; Sugiyama, T.; Koumoto, K. J. Mater. Chem. 2002, 12, 2643. (12) Masuda, Y.; Sugiyama, T.; Lin, H.; Seo, W. S.; Koumoto, K. Thin Solid Films 2001, 382, 153. (13) Shirahata, N.; Masuda, Y.; Yonezawa, T.; Koumoto, K. Langmuir 2002, 18, 10379. (14) Saito, N.; Haneda, H.; Sekiguchi, T.; Ohashi, N.; Sakaguchi, I.; Koumoto, K. AdV. Mater. 2002, 14, 418. (15) Gao, Y. F.; Masuda, Y.; Yonezawa, T.; Koumoto, K. Ceram. Soc. Jpn. 2002, 110, 379. (16) Masuda, Y.; Wakamatsu, S.; Koumoto, K. J. Eur. Ceram. Soc. 2004, 24, 301. (17) Gao, Y. F.; Masuda, Y.; Yonezawa, T.; Koumoto, K. Chem. Mater. 2002, 14, 5006. (18) Nakanishi, T.; Masuda, Y.; Koumoto, K. Chem. Mater. 2004, 16, 3484.
10.1021/la051538r CCC: $33.50 © 2006 American Chemical Society Published on Web 12/03/2005
Micropatterning of Cu on PET Substrate
Langmuir, Vol. 22, No. 1, 2006 333
Figure 1. Conceptual process for fabricating a micropattern of metallic copper thin film.
can damage the electrical properties of Cu because of its presence as a contaminant.19 Organosiloxane SAMs of alkylalkoxysilanes are chemisorbed on a Si substrate that has silanol groups (-SiOH) via Si-O-Si bonds.20 However, PET substrates do not have OH groups or other reactive groups on their surfaces9,21 to form SAMs. The buffer layer, which has silanol groups on its surface, must therefore be prepared on a PET substrate before the formation of SAMs. Silanol groups on the buffer layer can form Si-O-Si bonds with organosiloxane SAM molecules to act as a bridge between the SAMs and a substrate. On the other hand, alkanethiols have strong affinity to metal surfaces, such as Au, Ag, Cu, Pt, Fe, Ni, Pd, and alloys, and easily form well-ordered SAMs.22-24 In this study, we utilized a 3-mercaptopropyltrimethoxysilane (MPTS)-SAM as a template to fabricate a micropattern of metallic Cu thin films on a PET substrate. Because the MPTS molecule has both methoxy and thiol functional groups, it acts as an effective coupling agent between Cu and SiO2.25 Figure 1 shows the outline of our experimental procedure. A silica-like layer was prepared on a PET substrate and the MPTS-SAM was then formed on the silica-like layer. Cu thin film was deposited on the MPTS-SAM regions on a patterned SAM site-selectively because of the interactions between the Cu and the thiol groups. Cu was continuously deposited and metallized to form uniform thin films by autocatalysis. A micropattern of Cu thin film on a PET substrate was thus successfully fabricated without using a seed or etching process. (19) Zhu, P. X.; Mauda, Y.; Koumoto, K. J. Mater. Chem. 2004, 14, 976. (20) Styrkas, D. A.; Keddie, J. L.; Lu, J. R.; Su, T. J. J. Appl. Phys. 1999, 85, 868. (21) Chaudhury, M. K. Biosens. Bioelectron. 1995, 10, 785. (22) Vandenberg, E. T.; Bertilsson, L.; Liedberg, B.; Uvdal, K.; Erlandsson, R.; Elwing, H.; Lundstrom, I. J. Colloid Interface Sci. 1991, 17, 103. (23) Laibinis, P. E.; Whitesides, G. M.; Allara, D. L.; Tao, Y. T.; Parikh, A. N.; Nuzzo, R. G. J. Am. Chem. Soc. 1991, 113, 7152. (24) Laibinis, P. E.; Whitesides, G. M. J. Am. Chem. Soc. 1992, 114, 9022. (25) Huang, X.; Huang, H.; Wu, N.; Hu, R.; Zhu, T.; Liu, Z. Surf. Sci. 2000, 459, 183.
Experiment MPTS-SAM Preparation on PET Substrates. 1 vol % (3aminopropyl)trimethoxysilane (APTMS: NH2(CH2)3Si(OC2H5)3; Kishida Chemicals, Japan) was dissolved in acetone and aged for 2 weeks at room temperature. PET substrates were ultrasonically cleaned in acetone and ethanol, respectively, for 5 min and dried at 50 °C for an arbitrary length of time. The cleaned substrates were dip-coated with the acetone solution of APTMS and heated at 120 °C for 5 min to form a silica-like layer (thickness: 60 nm).26 By UV irradiation27 (wavelength: 184.9 and 254 nm, PL21-200, SEN Lights Co.) for 5 min, the substrates were wetted completely (water contact angle: ∼5°). The substrate with the silica-like surface layer was immersed in an anhydrous toluene solution containing 1 vol % MPTS for 1 h under an N2 atmosphere, then rinsed with anhydrous toluene. The resulting substrate was heated at 120 °C for 5 min in air to remove residual solvent and promote the chemisorption of the MPTSSAM. The SAM had -SH groups at the end of propylene chains and showed a water contact angle of 59°. The substrate with the SAM was irradiated by a UV lamp for 5 min through a photomask (Test chart No. 1 N-type, quartz substrate, 1.524 mm thickness, guaranteed line width of 2 ( 0.5 µm, Toppan Printing Co., Ltd.). The UV-irradiated surfaces of the SAM were modified to be hydrophilic (water contact angle: ∼5°) because of the formation of Si-OH groups, whereas the nonirradiated parts remained as SH groups. Alkylsilane SAMs were reported to be modified to silanol groups by photoinduced oxidation.28,29 UV-patterned SAMs with -SH/-OH terminated surfaces on PET were applied as templates to promote the site-selective deposition of copper to fabricate its micropatterns. Site-Selective Deposition of Copper Thin Films. Electroless bath solutions were prepared with CuCl2, boric acid (H3BO3), ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA(26) Zhu, P. X.; Teranishi, M.; Xiang, J. H.; Masuda, Y.; Seo, W. S.; Koumoto, K. Thin Solid Films 2005, 473, 351. (27) Masuda, Y.; Kinoshita, N.; Sato, F.; Koumoto, K. Cryst. Growth Des., in press. (28) Hong, L.; Sugimura, H.; Furukawa, T.; Takai, O. Langmuir 2003, 19, 1966. (29) Shirahata, N.; Yonezawa, T.; Seo, W. S.; Koumoto, K. Langmuir 2004, 20, 1517.
334 Langmuir, Vol. 22, No. 1, 2006
Sawada et al.
2Na) as a complexing agent, and dimethylamineborane (DMAB) as a reducing agent. NaOH was added to the solution to adjust the pH to 7.0. Expensive Pd or cancer-causing formaldehyde are widely used as catalysts for the electroless plating of copper;19 however, Cu can be deposited from a neutral (pH ) 7) aqueous solution without catalyst with this solution system. The PET substrates with SAM were immersed in the solution containing 0.05 M CuCl2, 0.1 M H3BO3, 0.05 M EDTA and 0.1 M DMAB and kept at 50 °C for 2 h to deposit Cu. Micropatterns of copper thin films were successfully fabricated on the modified PET surfaces. Characterization. The contact angle was detected by an FACE CA-D contact angle meter (Kyowa Interface Science Co., Ltd.; medium, distilled water). Deposited films were observed by an optical microscope (BX51WI, OLYMPUS Optical Co., Ltd.), a scanning electron microscope (SEM; S-3000N, Hitachi, Ltd.), and an atomic force microscope (AFM; SPI 3800N, Seiko Instruments Inc.). Structural information of the films was obtained by X-ray diffraction (XRD) analysis (RAD-1C, Rigaku; 0.5° incident angle, Cu KR, 40 kV, 30 mA). X-ray photoelectron spectroscopy (XPS; ESCA3300, Shimadzu Corp.; Mg KR, binding energies were referenced to the C(1s) hydrocarbon peak at 284.6 eV) and energy-dispersive X-ray (EDX) analysis (EDAX Falcon, EDAX Co., Ltd.), which is built into SEM, were used for surface analysis. Conductivity of a copper thin film was measured by the four-point probe method. The surface ζ potential of a substrate was measured by an electrophoretic lightscattering spectrophotometer (ELS-7300K, Otsuka Electronics Co., Ltd.) at 25°C.
Results and Discussion Pretreatment of PET Surface for SAM Fabrication. Generally, alkylsilane SAMs cannot be directly formed on a virgin polymer surface because alkylsilane SAMs require a hydroxylated surface as the substrate for their formation. Therefore, 3-aminopropyltriethoxysilane (APTES) was selected to form a polymeric silane structure containing Si-O-Si bonds on PET substrates.21,26,30,31 MPTS-SAM fabrication was realized on a modified PET substrate with a silica-like layer by dipcoating in an acetone solution of APTMS and treating with UV light. Topographic AFM images showed the surface morphologies of (a) PET, (b) the silica-like layer on PET, and (c) the UVirradiated silica-like layer on PET (Figure 2). The root-meansquare roughness (RRMS) of a, b, and c are 1.6, 0.4, and 0.3 nm, respectively, indicating that the surface became smooth as a result of the silica-like layer coating. After UV irradiation, the water contact angle decreased drastically from 51.8° to ∼5°, indicating that hydrophilic polymer was attained by UV irradiation. XPS spectra showed the surface modification of the PET films covered with the MPTS-SAM by UV irradiation (Figure 3). Si2s, C1s, N1s, and O1s were clearly observed from the MPTSSAM surface. Si and O were detected from the silica-like layer, which was mainly composed of Si-O-Si networks. C1s would be detected from surface contamination and residual organic components, such as -CH3, -CH2-, and so forth, in the silicalike layer, whereas N1s would be detected from residual NH2 and CdN-C in the layer. S2p was not observed by survey scan, and so the S2p spectrum was further measured by slow scan and integration mode. XPS analysis of the SAMs formed from monomolecular layers is known to require a long measurement period because of their thickness. Survey scan analysis shows that the MPTS-SAM is also a thin organic layer. The S2p peak observed before UV irradiation (a) disappeared after UV irradiation (b), and the water contact angle decreased by UV (30) Xiang, J. H.; Masuda, Y.; Koumoto, K. AdV. Mater. 2004, 16, 1461. (31) Kallury, K. M. R.; Krull, U. J.; Thompson, M. Anal. Chem. 1998, 60, 169.
Figure 2. Topographic AFM images of (a) PET, (b) the silica-like layer on PET, and (c) the UV-irradiated silica-like layer on PET. The root-mean-square roughness values (RRMS) of the substrate surfaces are (a) 1.6, (b) 0.4, and (c) 0.3 nm.
irradiation, as mentioned above. Thus it was confirmed that an MPTS-SAM having SH groups on the outermost surface was fabricated on the silica-like layer, and UV irradiation modified the surface from thiol to silanol groups, as evidenced by the extinction of an XPS peak and the decrease in water contact angle. The optical transmissions of the silica-like-layer-coated PET and the MPTS-SAM-modified PET were more than 80% in the
Micropatterning of Cu on PET Substrate
Figure 3. XPS spectra for PET films modified with an MPTSSAM (a) before and (b) after UV irradiation.
Figure 4. The optical transmissions and reflectance of (3) PET, (2) silica-like-layer-coated PET, and (0) MPTS-SAM-modified PET.
visible region, indicating that the transmittance was improved compared with that of PET. The silica-like layer and the MPTSSAM would act as antireflection films. The reflectance of the silica-like-layer-coated PET was slightly lower than that of PET in the 230-800 nm range. The decrease of reflectance would be attributed to the decrease of surface roughness observed by AFM, and the improvement of transmittance by the silica-like-layer coating would be caused by the reduction in reflectance. Site-Selective Deposition of Cu. By employing an MPTSSAM on silica-coated PET substrates, micropatterning of copper was successfully achieved. Figure 5 shows an optical micrograph of (a-c) the photomask, (d) the as-deposited film, and (e) the
Langmuir, Vol. 22, No. 1, 2006 335
magnified area of panel d. The white (-OH) and copper (Cu (-SH)) regions show the films deposited on UV-irradiated and nonirradiated surfaces, respectively. Although the site-selective deposition of Cu film is clearly seen in the MPTS-SAM region that had not been exposed to UV light, no deposition is observed on the UV-irradiated surface. The corners of the UV-irradiated square regions are rounded because of the imperfections of UV irradiation, such as bleeding of irradiation (Figure 5b,d). The line width of the UV-irradiated regions (Figure 5c) was about 5% narrower than that of the photomask (Figure 5e). This would be caused by the growth of Cu films and could be decreased by optimizing the deposition period to avoid excess film growth. The surface morphology and site-selective deposition were further evaluated by SEM with EDX and AFM (Figures 6, 7). The EDX mapping image indicates that Cu was deposited on the thiolsurface regions. The AFM image shows the surface morphology of Cu thin films. The RRMS of the Cu-deposited surfaces was estimated to be 8.9 nm, which is higher than that of PET (1.6 nm), the silica-like layer on PET (0.4 nm), and the UV-irradiated silica-like layer on PET (0.3 nm), and the difference in height between the deposited and nondeposited regions was about 80 nm by AFM observation. The XRD pattern of thin film deposited on the surface of the MPTS-SAM clearly indicates that it is a metallic copper film (Figure 8a). However, a small number of Cu depositions were observed on both MPTS-SAM regions and silanol regions in SEM micrographs. Such deposition can be avoided by controlling the solution conditions to reduce homogeneously nucleated Cu particles in the solution and by optimizing the surface modification process to reduce pinhole defects and roughness. The electrical conductivity of Cu film was 7.9 × 104 (S/cm), which is about 1 order of magnitude lower than that of standard Cu metal (5.8 × 105 (S/cm)32). The reason for such low conductivity is the fact that the Cu film is polycrystalline with small grains and grain boundaries that scatter electrons, thus reducing the conductivity. The high degree of supersaturation causes the rapid growth of Cu to form homogeneously nucleated particles in the solution as well as the growth of particulate film, which was constructed from many particles and had many grain boundaries. These grain boundaries reduce the electrical conductivity. Accordingly, to improve conductivity it is necessary to suppress the rate of crystal nucleation and enhance the crystal growth to accelerate grain growth and hence decrease the number of grain boundaries. Electroless deposition can be modified to have a low degree of supersaturation by decreasing the solution concentration, modifying the temperature, and so forth. A low degree of supersaturation would cause the slow deposition speed to form Cu films that are dense compared to those formed in a high degree of supersaturation. The electrical conductivity can thus be improved by decreasing the grain boundaries and enhancing the crystal growth that results from decreasing the supersaturation degree of the solution. The site-selective deposition of Cu does not differ according to the kind of substrate if a SH-terminated SAM can be formed on the substrate. A siloxane-type SAM and a thiol-type SAM can be used to modify the surfaces of solids. Siloxane-type SHterminated SAMs can be formed on substrates having OH groups such as glass, silicon, metal oxides, or metals having a thin natural oxide surface layer. Thiol-type SAMs can be formed on metal substrates such as Pt and Au. Cu patterning can thus be achieved on many kinds of substrates such as glass, silicon, metal oxides, polymers, or metals on which patterned thiol SAMs can be formed. (32) Electrical conductivity of the International Annealed Copper Standard (IACS) at 20 °C (1.7241 µΩ‚cm, 5.8 × 105 S/cm)
336 Langmuir, Vol. 22, No. 1, 2006
Sawada et al.
Figure 5. Optical microscope images of (a-c) the photomask, (d) the as-deposited film, and (e) a magnified area of d. The white (-OH) and copper (Cu (-SH)) regions show the films deposited on UV-irradiated and nonirradiated surfaces, respectively.
Figure 7. Topographic AFM image of Cu thin film. The rootmean-square roughness (RRMS) of the surface is 8.9 nm.
Figure 6. EDX analysis of the as-deposited film on a patterned MPTS-SAM: (a) SEM image and (b) characteristic X-ray image of Cu.
Mechanism of the Site-Selective Deposition of Cu. XPS analysis was carried out to investigate the initial growth behavior of Cu film at the beginning of the deposition process. Figure 9 shows the XPS spectra of PET substrates modified with an MPTS-SAM before (a) and after (b) Cu deposition. Spectrum
b was obtained from a Cu thin film on an MPTS-SAM after etching of the Cu thin film by Ar sputtering (2 kV, 20 mV, 5 min) to observe the S2p 3/2 spectrum at the interface between the substrate and the Cu thin film. The interactions of Cu with the MPTS-SAM are confirmed by the chemical shift in the binding energy of S2p. The S2p peak of the MPTS-SAM before deposition was observed at 163.4 eV (a). After deposition, the peak was shifted by 1.2 eV to the lower energy side (b). Based on this result, it is thought that Cu bonds to the thiol groups of the MPTS-SAM, and therefore S reacts with Cu to form Cu-S bonds.33,34 The component at 163.4 eV is assigned to the RS-H species, and that at 162.2 eV is assigned to the RS-Cu species. This result indicates that the site-selective adsorption of Cu occurred on the MPTS-SAM in the course of initial growth and that a micropattern of Cu thin film was formed with Cu-S chemical bonds. (33) Sandroff, J.; Herschbach, D. R. J. Phys. Chem. 1982, 86, 3277. (34) Hu, M. H.; Noda, S.; Tsuji, Y.; Okubo, T.; Yamaguchi, Y.; Komiyama, H. J. Vac. Sci. Technol. 2002, A20 (3), 589.
Micropatterning of Cu on PET Substrate
Langmuir, Vol. 22, No. 1, 2006 337
on a silicon wafer.19 The electrostatic interactions due to the difference in charge conditions between the Cu negative ζ potential and the patterned APTS-SAM surfaces (NH2: positive ζ potential, OH: negative ζ potential) are mainly responsible for the selective deposition of Cu particles on the NH2-SAM region. In the present case, however, the electrostatic interactions between the Cu and the MPTS-SAM appear to be repulsive since the ζ potential of the MPTS-SAM at pH 7.0 is rather negative, so the chemical affinity of Cu toward sulfur rather than electrostatic force should be more effective and responsible for site-selective deposition. Actually, Cu deposited more quickly and with better selectivity on the MPTS-SAM than on the APTS-SAM. Moreover, the adhesion was qualitatively improved because of the chemical bonds between the Cu and the sulfur.
Conclusions Figure 8. XRD patterns of as-deposited copper thin films on (a) an MPTS-SAM and (b) a UV-irradiated MPTS-SAM. (c) XRD pattern of PET.
Figure 9. XPS spectra of S2p for PET films modified with an MPTS-SAM (a) before and (b) after Cu deposition. Spectrum b was obtained from Cu thin film on an MPTS-SAM after etching by Ar sputtering.
We have already succeeded in micropatterning Cu thin film on the APTS-SAM with NH2 and OH functional groups patterned
We successfully fabricated a micropattern of Cu thin film on a PET substrate by electroless deposition using a SAM patterned with different functional groups (SH and OH terminal groups) as a template. PET substrate was first modified with a silica-like layer by being dip-coated in an acetone solution of APTMS and treated with UV light. Then, MPTS-SAM fabrication was performed on the modified PET substrate. We succeeded in the site-selective deposition of Cu only on thiol groups of the MPTSSAM by interfacial interactions between the surfaces of Cu and the modified PET substrate in a neutral solution without any catalysts by using DMAB as a reducing reagent. In addition, we confirmed that Cu adsorbed to the MPTS-SAM, forming Cu-S chemical bonds during the initial growth of Cu film. The siteselective deposition was achieved at low temperature using an SAM, molecular recognition, and the control of deposition conditions. Cu micropatterning can be realized on many kinds of substrates such as glass, silicon, metal oxides, polymers, or metals on which patterned thiol SAMs can be formed. This process can be further applied to other kinds of metal film formations and patterning of them on substrates of low heat resistance. Acknowledgment. This work was partially supported by Grants-in-Aid for Scientific Research (C) No. 17560595 from the Ministry of Education, Culture, Sports, Science and Technology, and the Foundation Hattori-Hokokai granted to Y.M. LA051538R
