F4280 Technology of Thin Film Deposition & Surface Treatments Lenka Zajíčková Faculty of Science, Masaryk University, Brno & Central European Institute of Technology - CEITEC lenkaz@physics.muni.cz spring semester 2024 E3RMO UNI1—ER5ITV OF" TECHNOLOGV UNI F4280/DS110 Introduction • 1. Field of Expertise, Suggested Literature • 1.2 Overview of Material Processing o 1.3 Introduction to Thin Film Deposition o 1.4 Applications of Thin Films • 1.5 Fabrication of microstructures/microdevices F4280/DS110 Field of Expertise, Suggested Literature ka Zajíčková 3/42 1. Field of Expertise, Suggested Literature F4280/DS110 1. Field of Expertise, Suggested Literature Lenka Zajíčková 4 / 42 What Expertise is Necessary? Dry material processing requires knowledge of ► gas kinetics (for processes from vapor/gas phase) ► film growth (general views like adsorption, desorption, utilization etc.) ► chemical kinetics (for chemical and plasmachemical methods) ► interaction of ions with solid (for ion beam and plasma techniques) ► plasma-related phenomena, i.e. plasma physics, principles of electrical discharges, elementary processes in plasma, plasma-surface interation The processes often takes places at decreased pressure. Therefore, a knowledge of vacuum technology is also required. This information are then applied to master the material processing techniques: ► etching (physical sputtering, chemical etching, plasma etching) ► vacuum evaporation for thin film deposition ► magnetron sputtering for thin film deposition ► chemical vapor deposition (CVD) ► plasma enhanced chemical vapor deposition (PEGVD) ► etc. F4280/DS110 1. Field of Expertise, Suggested Literature Lenka Zajíčková 5 / 42 What is Plasma? How to create it? Plasma is created from gas by adding sufficient energy (4th state of matter). Added energy leads to ionization of neutral gas, i. e. generation of electron-ion pairs: IP energy Plasma in thermal equilibrium has extremely high temperature (thermal plasma: fusion, sun) many plasmas are created out of thermodynamic equilibrium by increasing ionization : + ng) above the equilibrium value with an additional ionization source photoionization (Earth's ionosphere) photon ivjf!ct*d electron electron impact ionization (laboratory electrical discharges - electric field accelerates electrons) atom resulting ion F4280/DS110 1. Field of Expertise, Suggested Literature Lenka Zajíčková 6/42 Low temperature plasma of gaseous discharges provides unique environment for material processing: ► hot electrons (7"e few eV, 1 eV = 11 600 K) dissociation of molecules into reactive species e~ + AB —> A + B + e" ► positive ions that can be accelerated to hundreds of eV near a solid surface (in the plasma sheath) sputtering of targets, implantation, modification of surfaces and growing films ► cold neutral gas =>- highly energetic process can be kept in a vessel, heat sensitive materials can be treated (e.g., polymers) ► Handbook of Thin-Film Deposition Processes and Techniques, ed. K. K. Schuegraf, Noyes Publications 1988 ► Handbook of Plasma Processing Technology (Fundametals, Etching, Deposition, and Surface Interaction), ed. S. M. Rossnagel, J. J. Cuomo a W. D. Westwood, Noyes Publications 1989 ► Handbook of Ion Beam Processing Technology (Principles, Deposition, Film Modification and Synthesis), ed. J. J. Cuomo, S. M. Rossnagel, H. R. Kaufman, Noyes Publications 1989 ► Handbook of Plasma Immersion Ion Implantation and Deposition, Wiley 2000 ► Handbook of Thin Film Deposition Techniques (Materials and Processing Technology), by Krishna Seshan, (Noyes Publications 2002) ► Handbook of Nanotechnology (Springer 2010), B. Bushan F4280/DS110 1. Field of Expertise, Suggested Literature Lenka Zajíčková 8 / 42 Books Focused on Specific Processes and Technologies ► Thin Films Phenomena, K. L. Chopra, McGraw-Hill 1969 ► Thin-Film Deposition, Principles and Practice by Donald L. Smith, McGraw-Hill, 1995 ► Chemical reactor, analysis and design, G. F Froment and K. B. Bischoff, John Wiley 1990 ► Ion-Solid Interactions, Fundamentals and Applications, M. Nastasi, J. W. Mayer and J. K. Hirvonen, Cambridge University Press 1996 ► Principles of plasma discharges and materials processing, M. A. Lieberman and A. J. Lichtenberg, John Wiley 1994 ► Lecture notes on principles of plasma processing, F F Chen and J. P. Chang, Kluwer Academic 2003 F4280/DS110 1. Field of Expertise, Suggested Literature Lenka Zajíčková 9 / 42 ► Tribology of Diamond-like Carbon Films: Fundamentals and Applications, by Christophe Donnet and Ali Erdemir, Springer, 2008 ► Carbon Nanotubes: Science and Applications, M. Meyyappan ed., CRC Press 2004 ► The Science and Technology of Carbon Nanotubes, K. Tanaka, T Yamabe, F Fukui eds., Elsevier 1999 ► Nanostructures & Nanomaterials: Synthesis, Properties & Applications by Guozhong Cao, Imperial College Press, 2004 F4280/DS110 1.2 Overview of Material Processing ka Zajíčková 10/42 1.2 Overview of Material Processing F4280/DS110 urtace i reatmen Overview of Material Processing What can happen after surface treatment? ► change of surface roughness ► change of surface chemistry What can be these changes used for? ► change of surface free energy, i.e. wettability ► improved adhesion of further coatings ► immobilization of biomolecules Oregon Green C. Oehr etal., Surf. Coat. Technol. 116-119 (1999) 25-35 F4280/DS110 1.2 Overview of Material Processing Lenka Zajíčková 12/42 Preparation of Films Difference between thin-film and thick-film technology: ► thin-film technology: deposition of individual molecules, film thickness 10nm-10/iim thick-film technology: involves deposition of particles (e.g. painting, silk screening, spin-on-glass coating, plasma spraying) Plasmachemical methods compete with several other approaches on the field of thin film deposition and synthesis of nanostructures Several aspects have to be taken into account: ► functional properties of the deposition ► uniformity of the processes ► step coverage ► conformality ► reproducibility ► simplicity ► price ► etc. IT IT F i|. B. 3 a -d Step coverage and co uforma Lity: (a) poor step coverage, (b) good .step coverage, (c) iioiicoiiformaL layer, a lid (d) con formal Laver F4280/DS110 1.2 Overview of Material Processing Lenka Zajíčková 13/42 Etching/Sputtering Processes ion sputtering ► purely physical approach, removal by energy transfer ► slow process, no selectivity ► ions are directed by electric field, i.e. anisotropic process chemical etching ► purely chemical processes that requires aggressive chemicals and/or elevated temperature for reaction activation ► can be very fast, selective ► chemical reactions with surface are not directed, i.e. isotropic process plasma etching ► combination of physical and chemical approaches ► directional process b) Pro t'i Le for iin isctrap it etch through a photoresist rnuiidc a) Pit file for isotropic etch throujjh a pholorcsisl musk Pfaotoresiät fhotorasiM: J Silicon Hi o tore-.1: i s t Photnre i it Silicon F4280/DS110 1.2 Overview of Material Processing Lenka Zajíčková 14/42 Unique Features of I Plasma Technologies ► dry process, i.e. with low consumption of chemicals, ► offering replacement of toxic and explosive reactants ► environmentally friendly ► preparation of new materials Why? Plasma of laboratory electrical discharge provides environment of ► hot electrons (T « 10000 K) dissociation of molecules into reactive species ► positive ions that can be accelerated by « 100 eV near solid surface sputtering of targets, implantation, modification of surfaces and growing films ► cold neutral gas highly energetic process can be kept in a vessel, heat sensitive materials can be treated (e.g. polymers, even polymer nanofibers) F4280/DS110 Overview of Material Processing ka Zajíčková 15/42 cess Plasma etching anisotropic dry etching: combination of chemistry and effect of ions (reactive ion etching) © i .11 9 Malcrial atom 9 Activated rnütcTLiil ütnm VuLit i le product Maik m *1 ** ****** li ******** Í<£* i "'of 1 \l * . ********* ********** *. *. *. *. *• *, *. *.-. *. ™.p.'.W, TlP^ ••'-V' -. *. *■ ** -. *. *.'.'. V *• *•***■ ■* '»*•*• *»*»T* *»*»*• ■•**** Tm ****** >VV*J**i *»***•"» *•*• **>*•*■** '»*• V«>V f ** ******** ** *.*.-* 'tVm-m ****** *. ** ***. '* ****** ** ****** ** ****** ******** *.*■ *.*. ***.*#*. ***. .*.*,*,*.*.*.*,*.*.*.*,*,-.*.*,*.•.*,*,*.-.*.************» ** w»>>>>wW>*w5 Plasma treatment in 02, NH3, CF4 creation of surface chemical group CNT surface Plasma deposition of thin films plasma enhanced chemical vapor deposition (PECVD) Radicals Oligomers Ions MdUiHlW-M Substrate + electrodes + chamber walls physical vapor deposition (PVD) - dc diode sputtering, magnetron sputtering Ground shield - 1 Anode SÜDstrate J I Plasma Cathode (target) OQOOOOOOOOOOO wale* cooling T F4280/DS110 1.2 Overview of Material Processing Lenka Zajíčková 16/42 Commercial Plasma Reactors Plasma reactors can also look very differently, like plastic boxes :-) Oxford Instruments, PlasmaPro 100 - reactive ion etching Scalable and short process times • Sample size up to 8" wafer • Load lock wafer handling Flexible vapour delivery module for solids, liquid percursors' • Example: Mo(CO)6,MoCI5, W(CO)6 for 2D MoS2, WS2 et Plasma enabled CVD processes • Choice of in-chamber or remote ^. plasma (ICP) source High temperature heated table Oxford Instruments, NanoFab - high T (plasma enhanced) chemical vapor deposition for deposition of carbon nanomaterials and other 2D materials F4280/DS110 1.3 Introduction to Thin Film Deposition ka Zajíčková 17/42 1.3 Introduction to Thin Film Deposition F4280/DS110 1.3 Introduction to Thin Film Deposition Lenka Zajíčková 18/42 Thin-Film I Deposition Process Steps All thin-film processes contain the four (or five) sequential steps. 1. A source of film material is provided. Solid, liquid, vapor or gas source. Solid materials need to be vaporized (by heat or energetic beam of electrons, photons, i.e. laser ablation, or positive ions, i.e. sputtering) - physical vapor deposition (PVD). The methods using gases, evaporating liquids or chemically gasified solids are chemical vapor deposition (CVD) methods. 2. The material is transported to the substrate. The major issue is uniformity of arrival rate over the substrate area. Transport in a high vacuum = straight travelling lines —► importance of geometry. Transport in a (gaseous) fluid = many collisions —► gas flow patterns, diffusion of source molecules through other gases present. 3. The film is deposited onto the substrate surface. It is influenced by source and transport factors and the conditions at the deposition surface. Three principal surface factors: (i) surface condition (roughness, contamination, degree of chemical bonding with the arriving materials and crystallographic parameters in the case of epitaxy), (ii) reactivity of arriving material (sticking coefficient Sc from 1 to less than 10-3) and (iii) energy input (substrate heating, photons, ions, chemical energy). F4280/DS110 1.3 Introduction to Thin Film Deposition Lenka Zajíčková 19 / 42 4. (Optionally, annealing takes place) 5. The final step is analysis of the film. One level of analysis is the determination of functional properties important for given application and optimization of the deposition process for these processes (emphirical approach). A deeper level of analysis involves probing the film structure and composition (better understanding of the overall processes). Analysis of the films after deposition - kind of final process monitoring. However, monitoring is important in all steps! F4280/DS110 1.3 Introduction to Thin Film Deposition ka Zajíčková 20/42 method/processes specification evaporative techniques: thermal (vacuum) evaporation resistive heating flash evaporation arc evaporation exploding-wire technique rf heating electron-beam evaporation pulsed laser deposition (PLD) molecular beam epitaxy (MBE) liquid-phase chemical techniques: electro processes electroplating electrolytic anodization mechanical techniques spray pyrolysis liquid phase epitaxy gas-phase chemical techniques: chemical vapor deposition (CVD) CVD epitaxy metalorganic CVD (MOCVD) low-pressure CVD (LPCVD) atmospheric-pressure CVD (APCVD) atomic layer deposition (ALD) gas-phase physical-chemical techniques (except plasma and ion beam): modifications of CVD hot filament CVD (HFCVD) laser-induced CVD (PCVD) photo-enhanced CVD (PHCVD) electron enhanced CVD F4280/DS110 1.3 Introduction to Thin Film Deposition Lenka Zajíčková 21 / 42 Overview of Deposition Methods I - evaporative methods vacuum evaporation Coaling c.ir;iLL-.:l uLnm iegftssir^i; írom Lit hcsietl cojifiLVcioiifl pulsed laser deposition Power supply to heater Vacuum Chamber vacuum evaporation (resistive and electron beam "KZZZZZZ Source Sub&trale * r V a r. li 11 ni Evaporation 3utiilratfl J Electron Beam Rource Vacuum Resistive Healing n * r V ion-beam assisted deposition (IBAD) e-beam Evaporator Rotating Substrate Holder a Monitor Energetic Ion Source Vacuum Chamber dual ion-beam deposition ■"■■J Irüi"i ! .-ľ :;■ --in i F4280/DS110 1.4 Applications of Thin Films 1.4 Applications of Thin Films F4280/DS110 1.4 Applications of Thin Films ka Zajíčková 25/42 E verview of Applications Related to Particular Properties Optical properties ► Antireflection coating ► Filters (interference coatings) ► Decoration (color, color effects) Thermomechanical properties ► Scratch resistant coatings (hardness) ► Thermal protection/heat barriers ► Tribology (friction control, wear resistant films) (Bio)chemical properties ► Corrosion resistant coatings ► Permeation barriers ► Biocompatible surfaces, not-fouling surfaces (Photo)Electrical properties ► Conductors ► Insulators ► Semiconductor devices (microelectronics) ► Photovoltaic materials (sollar cells) Magnetic properties ► Magnetic storage devices F4280/DS110 1.4 Applications of Thin Films Lenka Zajíčková 26/42 Thin Films for Optical Applications AntirefLection coatings: n n I = r 12 + T23C -i2A 1 + rí2r^{-^ with n2 r llh.UHl _-— *00 450 500 6S0 600 6 SO 700 Wavelength (nm) F4280/DS110 1.4 Applications of Thin Films Lenka Zajíčková 27/42 Thin Films for Optical Applications Interference filters and mirrors: multilayer structure Important - control of film thickness, roughness (interface) and refractive index 2 DC ■1OQ0 0 10QO 2000 3000 4000 Distance from substrate [nm] 300 400 600 B00 1000 1200 1400 Wav&Jength [nm] F4280/DS110 1.4 Applications of Thin Films Lenka Zajíčková 28/42 Thin Films for Optical Applications Interference filters and mirrors: multilayer structure Important - control of film thickness, roughness (interface) and refractive index Mefrod Material Low Medum High ■ .....—"f--------j"'---1---- —_ ... - ■■ TT02:C:H< SiN13:H 1 Ĺ ■ ..........■ ........*...........■.......lij Q —1—..... 1 —j— ---1— — > O SiO^H PPOS PPHC< PPFC" ..... ^^^^^^H ----r- —. .. LU O. m r t j,---------4„._. L-------— --f----- -4- ■—t— i ......y- ■-■ -■ ■"'ŕ..... TtOs Ta2 CL [_____Í.........._____ -------r í ■ .......... ..... í______ . ■ t___ m ní 1_ PET PC SiO? glass PMMA^ SOj quartz ........* ......-i- -I i l ........\ f - i.......—h...... ; : ...i... 1 i ■ —j — co :....... i_. ■ F... -_j--- ---=- - ..... i ■ i 1.2 1,4 1.6 1-8 2-0 2.2 2.4 2.6 Refractive index n ai 550 nm FW. 2. Refractive index tat X = 550 nmi of diiTerenl PFCVD optical film materials; comparison with selected substrate and PVD malenafs. L WĽwilnu and D. Poíiras J. Vac. ScL Technol, A, Vol. 18 2619 F4280/DS110 1.4 Applications of Thin Films ka Zajíčková 29/42 Thin Films for Mechanical Protection Cutting tools: Which properties can be improved? What do we achieve with it? What are the challenges? Hardness - wear resistance, range of materiaLs Friction - wear resistance, cutting speed Thermal stability - cutting speed Heat conductivity - cutting speed Chemical stability - cutting speed and range of materiaLs Color - more attractive for customer Challenges: adhesion, cohesion, thermal expansion, chemical stability Complex shape of the object F4280/DS110 .4 Applications of Thin Films Lenka Zajíčková 30/42 Important - control of film thickness, roughness and uniformity Challenge - measurement of film properties at thickness < 3 nm F4280/DS110 1.4 Applications of Thin Films Lenka Zajíčková 31 /42 Thin Films for Mechanical Protection Tabte 12-1. Mechanical and Therm ni Proper lies of Coming Materials Melting or if Therm J Dcťomposiiicin (Ft) W-i) I i ■ i i. i -1 Therms Frittüre ľ ĺ nifjcrjluru Ů IJensily MihIiiIus Cotflkjtnl CundiKllviiy Toughness Milt rlil CC) l k K-min Ti ■ i ■ i . i 3) (Wra J K 1J 7.H 2 m) 14 .in Si) L 71) WC-ó%Cn 1500 640 5,4 MU ) 1 4 Ti IÉŔ7 251) I2Í) 11 1,1 SO N, SiJ-pc rnlliíys 1200 2I4 12 hl > 100 M. Ohring, The Materials Science of Thin Films F4280/DS110 1.4 Applications of Thin Films ka Zajíčková 32/42 Thin Films for Mechanical Protection Alloys can have properties superior to each component 500X3 4000 3000 ^ 2000 1000 )C řť) * 60 AO 100 Multilayer structures can combine properties of different compounds WOL% Figure 12-5. Microriardness of mined carbides due to solid solution and precipitation hardening I From Ret 3). M. Ohririg, The Materials Science of Thin Films S.E.M. \&m SXJM. i39M Figur* 12-fi. SEM irruícv uf CVD muJli layer iTJilinri fur Liming luol inscrti. (a) Carbide whrtTatc/TiC/TiCN.TiN (5500 x ). Carbide tubstmre TiC Al,0, TiN (3500 x ) iCourtcij of S Wrrthrimcr. ISC AR Ltd.) F4280/DS110 1.4 Applications of Thin Films ka Zajíčková 33/42 Thin Films as Barrier Protection Barrier coatings - permeation barriers J- 10s 1 > I I0U 10 4 * * + \i. DeilitiMn et ul Surface & Cm tings Technology 202 (2 nm thick SiO, film» for *utmus pulse power» -. -11 -i * 4 stun, -MK1 stun, /i V» I'll, 4 ms anJ i,„ 4 100nm ► NEMS - nanoscopic devices with characteristic length < 100nm MEMS/NEMS terms are also now used in a broad sense and include electrical, mechanical, fluidic, optical, and/or biological functions. They are referred to as intelligent miniaturized systems comprising e.g. sensing, processing and/or actuating functions. MEMS/NEMS for ► optical applications -micro/nanooptoelectromechanical systems (MOEMS/NOEMS), ► electronic applications - radio-frequency-MEMS/NEMS or RF-MEMS/RF-NEMS. ► biological applications - BioMEMS/BioNEMS. F4280/DS110 1.5 Fabrication of microstructures/microdevices Lenka Zajíčková 39 / 42 Dimensions of MEMS/NEMS in Perspective MEM5: CharacLerie,lie ler^Lh less Lhán 1 mm, larger Lhán 100 urn NEM5: Lest Lhan 1 00 nm Human hair 50-100 fim DMD 12 jim Molecular gear lOrim-lOOnm L—™ SWCNT LramisLor CaLomO.lůmn DNA 2.Sum i5nTri 0.1 1 10 1 00 1 000 10 000 1 00 000 5vae (nmj MEMS/NEMS examples shown are of a vertical single-walled carbon nanotube (SWCNT) transistor (5 nm wide and 15 nm high), of molecular dynamic simulations of a carbon-nanotube-based gear, quantum-dot transistor, and digital micromirror device (DMD http://www. dip. com) F4280/DS110 1.5 Fabrication of microstructures/microdevices Lenka Zajickova 40/42 Examples of MEMS - gears/motors TYavel direction MEMS motor was developped in lates 1980s using polycrystalline silicon (polysilicon) technology left-top photo shows micro-gears fabricated in mid-1990s using a five-level polysilicon surface micromachining technology (J. J. Sniegowski et al. IEEE Solid-St. Sens. Actuat. Workshop, 178-182 (1996)) - one of the most advanced surface micromachining fabrication process developed to date left-bottom SEM photo - microengine output gear and two additional driven gears gear extreme diameter is approximately 50 micrometers and gear thickness is 2.5 micrometers (J. J. Sniegowski et al.) t F4280/DS110 1.5 Fabrication of microstructures/microdevices ka Zajíčková abrica 41 /42 Two principle approaches can be used for micro/nanofabrication: top-down approach: ► deposition of thin films ► doping ► etching/sputtering (lithography, i.e. through a mask, and nonlitographic fabrication) anisotropic etching of Si ► preparation of surfaces (cleaning, polishing, functionalization) Lithography bottom-up ► building using nanoobjects (atoms, molecules), ► self-assemply of structures Synthetic Chemistry, Genetic Engineering, Top-Down mohla F4280/DS110 1.5 Fabrication of microstructures/microdevices Lenka Zajíčková 42/42 Lithography - process flow Microlithography is a technique that creates microstructures after given geometrical template: ► Lithography is usually applied to shape a thin film =>- deposition of thin film ► Photosensitive material (resist) is coated on the material that should be shaped ► Resist is irradiated through a mask, by projection of UV image or by directed electrons (photolitography or electron lithography) ► Resist development: ► positive resist: soluble in developper at the irradiated places ► negative resits: unsoluble in developper at the irradiated places ► Etching of the film through photoresist pattern ► Rest of the resist is removed Thin film deposition Thin JN Substrate PhoLoies ist coat big & development Mask P bot ores Is Thin film etching Pholoies ist ashing pLiirm plasma lithography patterning with positive resist