F4280 Technologie depozice tenkých vrstev a povrchových úprav 1. Introduction Lenka Zajíčková Přírodovědecká fakulta & CEITEC, Masarykova univerzita, Brno lenkaz@physics.muni.cz jarní semestr 2017 Central European Institute of Technology BRNO I CZECH REPUBLIC F4280 Technologie depozice a povrchových úprav: ka Zajíčková 2/40 utl line - c hapter' ntrod uction • 1.1 Fields of Expertise, Suggested Literature • 1.2 Overview of Material Processing 9 1.3 Introduction to Thin Film Deposition 9 1.4 Applications of Thin Films • 1.5 Fabrication of microstructures/microdevices F4280 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature ka Zajíčková 3/40 1.1 Fields of Expertise, Suggested Literature F4280 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature Lenka Zajíčková 4/40 What Expertise is Necessary? Material processing requires knowledge of processes: ► gas kinetics (for processes from vapor/gas phase) ► film growth (general views like adsorption, desorption, utilization etc.) ► interaction of ions with solid (for ion beam and plasma techniques) ► chemistry (for chemical and plasmachemical methods) ► 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 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature an Lenka Zajíčková 5/40 ► 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 ka Zajíčková F4280 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature ooks Focused on Specific Processes and Technologies 6/40 ► 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 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature Lenka Zajíčková 7 / 40 ► 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 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature cientific Papers ka Zajíčková 8/40 There are several electronic information resources http://knihovna.sci.muni.cz/: ► databases of scientific publications that collect information independently on the publisher and often contain links to full texts ► Web of Science Scopus ► INSPEC ► databeses of scientific publications from given publisher - always connected with full texts but the download must not be for free (depends on the institutional domain, e. g. sci.muni.cz), some journals are "open access" (authors pay for the publication) ► Science Direct ► lOPscience ► PROLA F4280 Technologie depozice a povrchových úprav: 1.1 Fields of Expertise, Suggested Literature Len ka Zajíčková 9/40 Related courses ► F4160 Vakuová fyzika 1 (jarní semestr) ► F6450 Vakuová fyzika 2 (podzimní semestr) F5170 Úvod do fyziky plazmatu (podzimní semestr) ► F7241 Fyzika plazmatu 1 (podzimní semestr) ► F7360 Charakterizace povrchů a tenkých vrstev (jarní semestr 2018) ► FB100 Plazmochemické procesy ► F3390 Výroba mikro a nanostruktur (jarní semestr) FC250 Nano- a mikrotechnologie (jarní semestr 2017) ► atd. F4280 Technologie depozice a povrchových úprav: 1.2 Overview of Material Processing ka Zajíčková 10/40 1.2 Overview of Material Processing F4280 Technologie depozice a povrchových úprav: urtace i reatmen 1.2 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 Technologie depozice a povrchových úprav: 1.2 Overview of Material Processing Lenka Zajíčková 12 / 40 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. Fig. B.Sa-d Step coverage and conformality: (a) poor step coverage, (b) good step coverage, (c) Qonconfonnal layer, mid (d) con format tayer F4280 Technologie depozice a povrchových úprav: 1.2 Overview of Material Processing Lenka Zajíčková 13/40 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 b) \?n\\ ilc for an i >io1 kj p ic etch through a photoresist mask ► directional process a) ťio f j le for isotropic etch throujjh a p ho tu it s ist musk Photoresist Photoresist J Silicon fll-. ■ I. ■■ -_■ -\-\ Photo re*; i s1 Silk oo F4280 Technologie depozice a povrchových úprav: 1.2 Overview of Material Processing Lenka Zajíčková 14/40 Unique Features of 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 Technologie depozice a povrchových úprav: 1.2 Overview of Material Processing ka Zajíčková 15/40 Plasma Processing Methods Plasma etching anisotropic dry etching: combination of chemistry and effect of ions (reactive ion etching) ©L u, 9 ľ-'..i:.: ľ I item 9 . V." 11 ■- .i ľ.1-.! 111 _ 11 -_-11:11 ate m VuLlilcproduĽl V "* V *#■ V '* *# Plasma treatment in 02, NH3, CF4 creation of surface chemical group CNT surface Plasma deposition of thin films plasma enhanced chemical vapor deposition (PECVD) SiH3 Ions Si3H3 Radicals Oligomers Ions physical vapor deposition (PVD) - dc diode sputtering, magnetron sputtering 1 Anode I Substrate ] Ground shield - Cathode (target) I Q y Q O O O O O O O O O Q Walep coohng T F4280 Technologie depozice a povrchových úprav: 1.2 Overview of Material Processing ka Zajíčková 16/40 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 mod for solids, liquid percursorsf • Example: Mo(CO)6,MoCI5, W(CO)6 for 2D MoS 2, WS2 etd 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 Technologie depozice a povrchových úprav: 1.3 Introduction to Thin Film Deposition ka Zajíčková 17/40 1.3 Introduction to Thin Film Deposition F4280 Technologie depozice a povrchových úprav: 1 1.3 Introduction to Thin Film Deposition Lenka Zajíčková 18/40 Thin-Film 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 Technologie depozice a povrchových úprav: 1.3 Introduction to Thin Film Deposition Lenka Zajíčková 19/40 in-Mim 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, is important in all steps! gas-phase physical-chemical techniques (except ion beam and plasma processes), method/processes specification evaporative techniques: thermal (vacuum) evaporation resistive heating flash evaporation arc evaporation exploding-wire technique laser evaporation rf heating electron-beam evaporation 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 Technologie depozice a povrchových úprav: 1.3 Introduction to Thin Film Deposition ka Zajíčková 21 /40 ervie method/processes specification plasma techniques: sputter deposition PECVD in low temperature discharges plasma processing in high temperature discharges dc sputtering rf diode sputtering magnetron sputtering dc discharge rf capacitively coupled plasma (CCP) rf inductively coupled plasma (ICP) microwave ECR deposition microwave resonantor reactor atmospheric pressure dielectric barrier discharge (DBD) atmospheric pressure glow discharge (APGD) atmospheric pressure surface barrier discharge etc. vacuum arc dc torch microwave torch etc. ion beam techniques: sputter deposition ion beam sputtering reactive ion beam sputtering ion deposition ion beam deposition ionized cluster beam deposition (ICB) dual processes ion beam assisted deposition (IBAD) dual ion beam sputtering F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films 1.4 Applications of Thin Films F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films Lenka Zajíčková 23/40 ► 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 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films ka Zajíčková 24/40 Thin Films for Optical Application« AntirefLection coatings: n < = >'i2 + r&e -i2A 1 + ruraar-'2* with rv/ = j and a = 0: V »i "3 + "a / with nx = 1 (air) an c «2 = v^š ^ R = 0! 100 TH r 50 1m JflWP ml ' 1Ü(tnm \ /l 0 nun 0 25 0. ŕ 0.35 1.0 1 .5 J n U J 0 3.5 4.0 4.5 S. 0 5. 5 ľ*1-1 6,5 7.0 6,0 4 0 iO 2,0 1.0 0.0 AR Coating Types -V typo It* Liyer MRI; f IIi.iii;! / __■ 40Ü 450 500 550 600 650 700 Wavelength (nm) F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films Lenka Zajíčková 25/40 Interference filters and mirrors: multilayer structure n h Important - control of film thickness, roughness (interface) and refractive index e x ■i Ľľ ■1O0O O 1000 2000 3000 4000 Distance from substrate (nm] 200 400 600 600 1000 1200 1400 Wav^ength [nm] D92-B F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films Lenka Zajíčková 26/40 Thin Films for Optical Applications Interference filters and mirrors: multilayer structure Important - control of film thickness, roughness (interface) and refractive index Method Malena > Ü LU CL > Cl (D -Q try Low Medům Higr Tug TaZ°5 SiM, 3;H PP05 PPHC so^f PPFC TÍO2 ZrOj Al203 StOs MflF2 PET PC SiO? glass PMMA íl- -í-.......— '• í 4- -L i- ■f-i- 1.2 1.4 1-6 1-8 2-0 2.2 2.4 Refractive index n at 560 nm 2-6 Fir.. 2- Refractive index iat A = 550 nm> of different PFCA D optical film materials; comparison with selected substrate and P\'D maleriaJs. L Muri I n li and D. Poílras j. Vac. Sc L Technol. A, Vol. 16 2619 F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films Lenka Zajíčková 27/40 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 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films ka Zajíčková 28/40 Thin Films for Mechanical Protection Re ad/Write head Disk write coil GMR read element carbon c Ö a. 100 frif 30 -20 10 : 5 '-3 - :; magnetic spacing lubncant carbon^. CoClPt Magnetic layer substrate Magnetic spacing -j_1_l_j_l—l—L 5 10 20 50 100 Storage density (Gbits/in.2) year 2000 function: corrosion protection and triboLogy enhancement Important - control of film thickness, roughness and uniformity Challenge - measurement of film properties at thickness < 3 nm 200 2005: 150 Gbit/in2 F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films Lenka Zajíčková 29/40 Thin Films for Mechanical Protection Table 12-1, Mediisnica! and Therm li I Pioperlics of Coating MutcriiiJs Melt i r j; it Tlie mul Dcťoinpnsiijcin taparmon Thermut ľl dl Hli Ľ 1 v' ilipculurĽ Hiif dnuwi jj 1 Jensiily Mii' il. ■ Cmflkiidl ton d u t tidily Toughness Milt rial PO ik ■ ■ m, J> ■ \ • i ■ ' !) on 1 c■ '> f (-cm 'l (kN-rnm J) (10 *K b) IWm J K 1J [.....L 21 Hl) 231)0 7.85 3.9H ft.S - 2.5 3.5 1HŮ7 1101) 1250 s.» 4.25 MU 9 ?i67 111 U I.'-IHI í 7i 20« 8.U 1.9 4-12 too, 1700 HOD 3.2? 151 fi.^ 2 < 1 C (Diamond) 38on 153 L OH t 11110 U 3.Ů2 15.7 720 4,0 Maltrlaiji High-SpjťťJ SlL v L 140 U 0(10 T,S 2.^ u 14 Síl 17í) 1500 640 5,4 MU ] 1 4 Ti IÚĚ7 43 120 11 13 «0 1280 7,9 214 12 62 > 100 M. Ohríng.The Materials Science of Thin Films F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films ka Zajíčková 30/40 Thin Films for Mechanical Protection Alloys can have properties superior to each component f*C Multilayer structures can combine properties of different compounds 0 20 40 60 «0 100 WOt % Figure 12-5. Mitrohardncss of nined carbide* due to solid solution and precipitation hardening (From Ref. 5). M. Ohring, The Materials Science of Thin Films TV Flguri 134. SEM imj^rv uf CVD muJli lavr r iiiílinsi fur Luľjnu tut'l invert!, (a) Carfcidc ™hs«™wr/TtC/TiCNŕTiN (5500 x ). (bi Carfcidí tubstme TiC AljO, TiN 0500 X ) (Ccmrtciy of S Wrrthrimcr. ISCAR LlJ i F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films ka Zajíčková 31 /AO Thin Films as Barrier Protection Barrier coatings - permeation barriers inno >om iooo -won Pf w Fig. J. Pcrmcabon ate* of Ml nm thick SiO, h Im» for vbtkhi1* [ml*- |n-.^.rs 600 WsPi3000 WM pl«sma cumliiions *hmikso ■* *cm. *OJ-400 ran, f Vi Pi. t.m 4 ire and t..a 40 m v F4280 Technologie depozice a povrchových úprav: 1.4 Applications of Thin Films Lenka Zajíčková 32/40 Thin Films as Barrier Protection Barrier coatings - permeation barriers Practical problem: Bottels are filled at pressure of ~ 6 bar! I'i^nri' 7. srm micrograph K of sioT films on pft after ? h etching in CCP cnygtrn plasma. Important: adhesion, microstructure (defects), elasticity, biocompatibility F4280 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices 1.5 Fabrication of microstructures/microdevices F4280 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices ka Zajíčková 34/40 Microelectronics - Fabrication of Integrated Circuits Increase of integration: ► Small-Scale Integration (SSI) few transistors on chip, ► Medium-Scale Integr. (MSI) hundreds of transistors on chip (end of 60ties), ► Large-Scale Integration (LSI) 10 000 transistors on chip (70ties), ► Very Large-Scale Integr. (VLSI) 100 000 transistors on chip (begining of 80ties), 1 000 000 000 in 2007 AMD-AthJon Am486 I._: H|i.„. i. HL.- 0,35^(1,300,000) 0,15^(9,000,000) JW TSj.....1 Microprocessor Transistor Counts 1971-2011 & Moore's Law c 13 O o O -t—' C/3 'cß £Z 03 2,600,000,000-, 1,000,000,000- 100,000,000 10,000,000- 1,000,000- 100,000- 10,000-2,300 curve shows transistor count doubling every two years 8008» "j «MOS 6502 4004»/RCA 1802 16-Core SPARC T3 Six-Core Core i7^ Six-Core Xeon 7400 • 10-Core Xeon Westmerg-EX Dual-Core Itanium 29 AMD K10 POWER6' Itanium 2 with 9MB cache• _ /z\ ^Six-Core Opteron 2400 6#y \. 8-core POWER7 Quad-core z196 Quad-Core Itanium Tukwila 8-Core Xeon Nehalem-EX AMD K10« Core i7 (Quad) J Core 2 Duo 1971 0,lSjj(J7vOOO,000) liůmmJ 1980 1990 Date of introduction Source - www.wikipedia.org 2000 2011 F4280 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices ka Zajíčková 35/40 Microelectronics - Fabrication of Integrated Circuits ► Front-end-of-line (FEOL) structure: complementary metal-oxide-semiconductor (CMOS) technology is the dominant semiconductor technology for microprocessors, microcontrollers, static RAM and other ICs NMOS PMOS BS D S DB nwell CMOS uses complementary and symmetrical pairs of p-type and n-type metal oxide semiconductor field effect transistors (MOSFETs) for logic functions. p-wibstrate ► Back-end-of-line (BEOL) structure: interconnect metallization, Cu instead of Al and low-k materials are used to decrease the R and C, i.e. BEOL delay. SEM view of three levels of copper interconnect metallization in IBM's CMOS integrated circuits (Photograph courtesy of IBM Corp., 1997.) Global Intermediate --< Passivation Dielectric ■ Etch Stop Layer - Dielectric Capping Layer Copper Conductor with Bamer/Nucleation Layer Metal 1 —C P Pre-Metal Dielectric Tungsten Contact Plug Metal 1 Pitch The acronym MEMS/NEMS (micro / nanoelectromechanical systems) originated in the USA. The term commonly used in Europe is microsystem technology (MST), and in Japan it is micro/nanomachines. Another term generally used is micro/nanodevices. ► MEMS - microscopic devices with characteristic length < 1 mm and > 100 nm ► NEMS - nanoscopic devices with characteristic length < 100 nm 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 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices Lenka Zajíčková 37 / 40 Dimensions of MEMS/NEMS in Perspective MEMS: C harac le-ri l Líc ler^Lh len lhan 1 mm, larger Lhan 100 nm NEM5: Lsll Lhan 1 00 nrn C aLom 0.1 ůnm 0.1 DMD 12 u.m QuanLum-doL LransiiLor 300nm Red blood cell S fim Molecular gear lOnrn-lOOTirn 1 5WCNT Lrantitlor DNA 2.5ti tti 15flm 1 10 100 1000 10 000 Human hair 50-100 fim 100 000 Siie (nm) 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 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices Lenka Zajíčková 38/40 Examples of MEMS - gears/motors ***zrw&&**^ zkum +- TYavel dinecJion 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.) 1- F4280 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices Lenka Zajíčková 39/40 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 Bottom-Up Top-Down Synthetic Chemistry, Genetic Engineering, F4280 Technologie depozice a povrchových úprav: 1.5 Fabrication of microstructures/microdevices ka Zajíčková 40/40 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 ThltifU Substrate Pholoies isl coat ing & development Photo its ist ashing plasma lithography patterning with positive resist