Linear Ion Beam Applications for Roll-to-Roll Metal Thin Film Coatings on PET Substrates

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1 Research Paper Applied Science and Cnvergence Technlgy Vl.24 N.5, September 2015, pp Linear In Beam Applicatins fr Rll-t-Rll Metal Thin Film Catings n PET Substrates Seunghun Lee and D-Geun Kim* Plasma Prcessing Labratry, Divisin f Surface Technlgy, Krea Institute f Materials Science, Changwn 51508, Krea (Received September 10, 2015, Revised September 23, 2015, Accepted September 24, 2015) Linear in beams have been intrduced fr the in beam treatments f flexible substrates in rll-t-rll web cating systems. Ande layer linear in surces (300 mm width) were used t make the linear in beams. Oxygen in beams having an in energy frm 200 ev t 800 ev used fr the adhesin imprvement f Cu thin films n PET substrates. The Cu thin films depsited by a cnventinal magnetrn sputtering n the xygen in beam treated PET substrates shwed Class 5 adhesin defined by ASTM D (tape test). Argn in beams with 1 3 kev used fr the in beam sputtering depsitin prcess, which aims t cntrl the initial layer befre the magnetrn sputtering depsitin. When the discharge pwer f the linear in surce is 1.2 kw, static depsitin rate f Cu and Ni were 7.4 and 3.5 Å/sec, respectively. Keywrds : In beam, In surce, Sputtering, Surface treatment, Rll-t-rll I. Intrductin Metal thin films n flexible plymer substrates are ne f the mst imprtant parts in flexible electrnics such as tuch screen panel, display, and energy harvesting device. The thin films shuld be satisfied several requirements fr the flexible applicatins. Fr example, the thin films have t be adhesive n the flexible substrates during >500,000 times bending test. There are many methds t imprve the adhesin by cntrlling a tp-mst layer f plymer [1]. Als a sheet resistance shuld be lw enugh t ignre a pwer cnsumptin in the thin films. Plasma assisted depsitin, electrn beam irradiatin, substrate heating, pulsed light annealing have been investigated t enhance the sheet resistance f the depsited thin films [2,3]. Nevertheless, there are cntinuus needs t meet the industrial requirements fr the high-end prduct f flexible electrnic devices. Rll-t-rll (R2R) vacuum cating technlgies have been used t prepare the metal thin films because f gd quality and ec-friendly prcess cmparing t a wet prcess. Thermal evapratin and magnetrn sputtering are representative methds fr the R2R thin film depsitin. The thermal evapratin has a high depsitin rate and large width unifrmity. The magnetrn sputtering als has varius merits such as linear expandable gemetry, wide prcess windw, and s n. Hwever, these are nt easy t meet the requirements themselves fr the flexible * [ ] dgeunkim@kims.re.kr

2 Linear In Beam Applicatins fr Rll-t-Rll Metal Thin Film Catings n PET Substrates applicatins. Plasma r electrn assisted methds have been applied t the evapratin and magnetrn sputtering [4,5]. described in ur previus wrk [6]. And magnetrn sputter depsited 200 nm Cu thin films ne the PET as a dynamic depsitin rate, 50 nm m/min. Recently a linear in surce (LIS) is ne f the In the Ar in beam sputtering prcess, the LIS was prmising candidates fr advanced R2R vacuum perated with 4 kv discharge vltage. The sputtered catings because the R2R prcesses need a linearly targets were Cu and Ni. The depsitin rate was treatable methd, nt a pint surce. The LIS has calculated by measuring the thickness f the metal been investigated intensively fr the R2R surface thin films n Si substrates. treatments frm 2010s [6,7]. The LIS uses crssed electrmagnetic fields t cnfine electrns in a linearly clsed lp. The crssed fields result in electrn III. Results and Discussin drifts called as E crss B drift. The drifting electrns inize neutral gases such as argn, xygen, 1. In beam pretreatments fr the adhesin im- hydrgen, and nitrgen. Then the ptential drp near prvement f Cu thin films n PET substrates an ande layer emits the inized gases. The cntrllable in energy is frm kev. The lw energy in The tpmst layer mdificatin f PET films is ( 0.3 kev) is useful t treat plymer surfaces t mdify the tp-mst layer and remve rganic impurities. And the high energy in ( 1 kev) can be adaptable t in beam sputtering depsitins due t a high sputtering yield. In this paper, we have intrduced the LIS applicatins in R2R cating system. One is the xygen in beam pretreatment prcess fr the adhesin imprvement f Cu thin film n PET substrates. The ther is the Ar in beam sputtering depsitin f Cu and Ni thin films. II. Experimental Setup The R2R cating system cnsists f the LISs and magnetrn sputters as shwn in Fig. 1. The cating width is 300 mm and a web speed is cntrllable frm 0.1 t 10 m/min. In the adhesin imprvement prcess, PET (PANAC, 188 um) was used fr the flexible substrate. The ande layer type LIS used t the pretreatment. The discharge vltage was kv t cause functinalizatin and etching with xygen gas. The specific cnditins fr PET pretreatments are Figure mm width rll-t-rll cating system. 163

3 Seunghun Lee and D-Geun Kim imprtant t btain a gd adhesin. The frmatin IBSD can cntrl the crystallinity f depsited thin f carbnyl grup results in a high surface energy, films withut a substrate heating. In the IBSD, the which enhances the adhesin between Cu and PET. In averaged energy f sputtered neutral atms frm a the R2R system, the LIS generates xygen ins fr sputtering target culd be higher than that f making carbnyl grups n PET surface. The xygen cnventinal magnetrn sputtering because the energy ins have wide energy distributins frm 200 t 800 f impinging ins is in kev ranges, which is enugh ev as described elsewhere [6]. S the functinalizatin t increase the energy f sputtered neutral atms by and the terminatin f free radical are available inelastic mmentum cllisins. This phenmena has simultaneusly. Our previus wrk has reprted that been reprted in similar sputtering apparatus using a the xygen in beam makes rugh PET surfaces remte plasma sputtering [8]. The crystallinity cntrlled functinalized t carbnyl grups [6]. The xygen in initial layer affects the crystallinity f depsited beam treatment shwed gd adhesins in the R2R Cu layer in fllwing magnetrn sputtering depsitin in depsitin prcess. Fig. 2 is the ptical image f tape R2R prcess. Thus, lw sheet resistance metal thin adhesin test. ASTM D was used t classify films n plymer substrates are available withut a the adhesin perfrmance. In this evaluatin methd, substrate heating. And the linear in beam prper t crssly scratched thin films are detached by 3M the R2R system requiring linear surface treatments. adhesive tapes. Cu thin films n bare PET substrate A cnventinal LIS emits parallel in beams shwed wick adhesin srted t Class 0. Hwever, the because the directin f accelerating electric field is Cu thin films n xygen in treated PET samples had same. As a result, the linear in beam t sputter a gd adhesin classified t Class 5. Als the sheet metal target shwed unfcused trajectry as shwn in resistance f the Cu thin film (200 nm) als have been Fig. 3(a). This cnfiguratin has n prblem t induce imprved frm 3.16±0.20 Ohm/sq. t 2.72±0.04 an in beam sputtering. Hwever, we need t increase Ohm/sq. in the pretreated samples. the depsitin rate f IBSD due t its lw in flux cmparing t the magnetrn sputtering. It is well- 2. In beam sputtering depsitin using a linear in surce knwn that the ptimum incident angle t maximize a sputtering yield is frm the nrmal directin f sputtering target [9]. When the parallel The LIS have been investigated t the in beam in beam is tilted, ne can easily find a limitatin t sputtering depsitin (IBSD) fr R2R vacuum cating fcus the in beams t the sputtering target because system. The IBSD has several advantages. Cmparing the target area is nt large in R2R system. Thus, t cnventinal magnetrn sputtering prcesses, the fcused in beam is required in R2R system as shwn Figure 2. The ptical images f Cu adhesin testing samples. (a) Withut xygen in beam pretreatment (left), (b) With xygen in beam treatment (right). 164 Appl. Sci. Cnv. Technl. 24(5), (2015)

4 Linear In Beam Applicatins fr Rll-t-Rll Metal Thin Film Catings n PET Substrates Figure 3. The discharge images f in beam sputtering apparatus. (a) Parallel linear in beam (left), (b) Fcused linear in beam (right). and 3.5 Å/sec when the electrical pwer cnsumptin is 1.2 kw in the LIS and the incident angle is The depsitin sample was lcated at the intersectin pint between the substrate hlder and the center f sputtering target. These depsitin rate is abut 1/5 1/6 f the maximum depsitin rate f cnventinal magnetrn sputtering with the pwer 2 density, 38.7 W/cm [11]. IV. Cncluding Remark The linear in beams have been utilized surface treatments prcesses f rll-t-rll web cating systems. The linear in beams generated by ande layer linear in surces are easy t be mdulated fr Figure 4. In trajectries calculated by OOPIC numerical cde at the discharge slit. (a) Parallel linear in beam (left), (b) Fcused linear in beam (right). varius surface treatments requiring diverse in energies because the in energy is prprtinal t the ande vltage. And the linear in surce prduces varius in beams such as argn, hydrgen, xygen, in Fig. 3(b). The IBSD with the ptimum incident nitrgen, and s n by inizing discharge gases. angle is available by the fcused linear in beams. In Thus, the linear in beams culd be attractive tech- the fcused linear in beams, the asymmetric cathde nlgies fr rll-t-rll web cating systems. has been used t tilt the directin f accelerating electric field. The in trajectries can be mdulated by the cathde cnfiguratin as shwn in Fig. 4, Acknwledgements which is calculated in trajectry by OOPIC [10]. When the psitin f cathde has an angle t an This research was financially supprted by the ande nrmal vectr, the emitting ins are tilted Sensitivity tuch platfrm develpment and new fllwing the tilting electric field as represented t industrializatin supprt prgram thrugh the Ministry dtted lines in Fig. 4. f Trade, Industry & Energy (MOTIE) and Krea The static depsitin rate f Cu and Ni were Institute fr Advancement f Technlgy (KIAT). 165

5 Seunghun Lee and D-Geun Kim References [1] KYUNG WHA OH, DONG JUN KIM, SEONG HUN KIM, Jurnal f Applied Plymer Science, 84, (2002). [2] S. Laux, N. Kaiser, A. ZÈller, R. GÈtzelmann, H. Lauth, H. Bernitzki, Thin Slid Films 335, 1-5 (1998). [3] Wri D,Wn-Bem Jin, Jungwan Chi, Seung- Muk Bae, Hyung-June Kim, Byung-Kuk Kim, Seungh Park, Jin-Ha Hwang, Materials Research Bulletin 58, (2014). [4] Min Zhu, Y. Makin, M. Nse, K. Ngi, Thin Slid Films 339, (1999). [5] Y.S. Kim, S.B. He, H.M. Lee, Y.J. Lee, I.S. Kim, M.S. Kang, D.H. Chi, B.H. Lee, M.G. Kim, Daeil Kim, Appl. Surf. Sci. 258, (2012). [6] Seunghun Lee, Eun-Yen Byun, Jng-Kuk Kim, D-Geun Kim, Current Applied Physics 14, S180-S182 (2014). [7] S. Lee, J.-K. Kim, D.-G. Kim, Rev. Sci. Instrum. 83, 02B703 (2012). [8] Seunghun Lee, Jng-Kuk Kim, Jae-Wk Kang, D-Geun Kim, Surf. Cat. Technl. 206, (2012). [9] H. Kitani, N. Tyda, J. Matsu, I. Yamada, Nucl. Instr. und Meth. in Phys. Res. B I2 I, (1997). [10] J. P. Verbnceur, A. B. Langdn, and N. T. Gladd, Cmput. Phys. Cmmun. 87, 199 (1995). [11] php 166 Appl. Sci. Cnv. Technl. 24(5), (2015)