Selective Laser Ablation of Metal Thin Films Using Ultrashort Pulses

다국어 초록 (Multilingual Abstract)

Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron–phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.

참고문헌 (Reference)

1 Robinson, P. J., "Why gold is the noblest of all the metals" 376 : 238-240, 1995

2 최장희, "Wavelength dependence of the ablation characteristics of Cu(In,Ga)Se2 solar cell films and its effects on laser induced breakdown spectroscopy analysis" 한국정밀공학회 3 (3): 167-171, 2016

3 Yuwen Zhang, "Ultrafast melting and resolidification of gold particle irradiated by pico- to femtosecond lasers" AIP Publishing 104 (104): 054910-, 2008

4 J. Hohlfeld, "Time-resolved thermoreflectivity of thin gold films and its dependence on film thickness" Springer Science and Business Media LLC 64 (64): 387-390, 1997

5 J. Bovatsek, "Thin film removal mechanisms in ns-laser processing of photovoltaic materials" Elsevier BV 518 (518): 2897-2904, 2010

6 J. P. Moore, "Thermal conductivity, electrical resistivity, and Seebeck coefficient of high‐purity chromium from 280 to 1000 K" AIP Publishing 48 (48): 610-617, 1977

7 Bryan C. Gundrum, "Thermal conductance of metal-metal interfaces" American Physical Society (APS) 72 (72): 1-5, 2005

8 J. K. Chen, "The role of electron–phonon coupling in ultrafast laser heating" Laser Institute of America 17 (17): 63-68, 2005

9 M. Bouhadja, "Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers" AIP Publishing 140 (140): 234507-, 2014

10 Laurent Cormier, "Relationship Between Structure and Glass Transition Temperature in Low-silica Calcium Aluminosilicate Glasses: the Origin of the Anomaly at Low Silica Content" Wiley 88 (88): 2292-2299, 2005

11 Anisimov, S. I., "On the theory of ultrashort laser pulse interaction with a metal" 61 (61): 1642-1655, 1997

12 Bülent Öktem, "Nonlinear laser lithography for indefinitely large-area nanostructuring with femtosecond pulses" Springer Science and Business Media LLC 7 (7): 897-901, 2013

13 Stuart, B., "Nanosecond-to-femtosecond laser-induced breakdown in dielectrics" 53 (53): 1749-1761, 1996

14 Hoon-Young Kim, "Morphologies of femtosecond laser ablation of ITO thin films using gaussian or quasi-flat top beams for OLED repair" Springer Science and Business Media LLC 124 (124): 1-8, 2018

15 Jaegu Kim, "Metal thin film ablation with femtosecond pulsed laser" Elsevier BV 39 (39): 1443-1448, 2007

16 Liang Pan, "Maskless Plasmonic Lithography at 22 nm Resolution" Springer Science and Business Media LLC 1 (1): 1-6, 2011

17 Hyeon-Min Lee, "Machining Characteristics of Glass Substrates Containing Chemical Components in Femtosecond Laser Helical Drilling" 한국정밀공학회 8 (8): 375-385, 2021

18 허준연, "Laser Micromachining of Permalloy for Fine Metal Mask" 한국정밀공학회 2 (2): 225-230, 2015

19 Ashutosh Giri, "Influence of Hot Electron Scattering and Electron–Phonon Interactions on Thermal Boundary Conductance at Metal/Nonmetal Interfaces" ASME International 136 (136): 1-6, 2014

20 추원식, "Hybrid Manufacturing in Micro/Nano Scale: A Review" 한국정밀공학회 1 (1): 75-92, 2014

21 Chowdhury, I. H., "Heat transfer in femtosecond laser processing of metal" 44 : 219-232, 2003

22 Liang Guo, "Heat Transfer Across Metal-Dielectric Interfaces During Ultrafast-Laser Heating" ASME International 134 (134): 042402-, 2012

23 Ihtesham H. Chowdhury, "HEAT TRANSFER IN FEMTOSECOND LASER PROCESSING OF METAL" Informa UK Limited 44 (44): 219-232, 2003

24 Chichkov, B. N., "Femtosecond, picosecond and nanosecond laser ablation of solids" 63 (63): 109-115, 1996

25 M. Saghebfar, "Femtosecond pulse laser ablation of chromium: experimental results and two-temperature model simulations" Springer Science and Business Media LLC 123 (123): 1-9, 2017

26 Rafael R. Gattass, "Femtosecond laser micromachining in transparent materials" Springer Science and Business Media LLC 2 (2): 219-225, 2008

27 Bieda, M., "Fabrication of sub-micron surface structures on copper, stainless steel and titanium using picosecond laser interference patterning" 2016

28 Zhibin Lin, "Electron-phonon coupling and electron heat capacity of metals under conditions of strong electron-phonon nonequilibrium" American Physical Society (APS) 77 (77): 1-17, 2008

29 Hohlfeld, J., "Electron and lattice dynamics following optical excitation of metals" 251 (251): 237-258, 2000

30 Patrick E. Hopkins, "Effects of electron scattering at metal-nonmetal interfaces on electron-phonon equilibration in gold films" AIP Publishing 105 (105): 023710-, 2009

31 Yan Wang, "Effect of interlayer on interfacial thermal transport and hot electron cooling in metal-dielectric systems: An electron-phonon coupling perspective" AIP Publishing 119 (119): 065103-, 2016

32 Anatoliy Y. Vorobyev, "Direct femtosecond laser surface nano/microstructuring and its applications" Wiley 7 (7): 385-407, 2013

33 D. Canteli, "Characterization of direct- and back-scribing laser patterning of SnO2:F for a-Si:H PV module fabrication" Elsevier BV 271 : 223-227, 2013

34 Kerse, C., "Ablation-cooled material removal with ultrafast bursts of pulses" 2016

35 Chen, J. K., "A semiclassical two-temperature model for ultrafast laser heating" 49 (49): 307-316, 2006