FC250 Nano- and microtechnologies chapter 1. Introduction Lenka Zajíčková Přírodovědecká fakulta & CEITEC, Masarykova univerzita, Brno lenkaz@physics.muni.cz spring semester 2017 Central European Institute of Technology ^ U*I# i BRNO | CZECH REPUBLIC ^*SL*f^ FC250 Nano- and microtechnologies: Outline - chapter 1. Introduction • 1.1 Fields of Expertise, Suggested Literature • 1.2 Approaches in Micro/Nanotechnologies • 1.3 Overview of Top-Down Fabrication • 1.4 Plasma Technologies 9 1.5 Examples of Bottom-Up Fabrication o 1.5 Fabrication of micro- and nanodevices FC250 Nano- and microtechnologies: 1.1 Fields of Expertise, Suggested Literature ka Zajíčková 3/37 1.1 Fields of Expertise, Suggested Literature Nanotechnology definition: ► Any technology on a nanoscale that has applications in the real world, (from Handbook of Nanotechnology) ► Research and technology development at the atomic, molecular, or macromolecular levels, in the length scale of approx. 1-100 nm range, to provide a fundamental understanding of phenomena and materials at the nanoscale and to create and use structures, devices, and systems that have novel properties and functions because of their small and/or intermediate size. The novel and differentiating properties and functions are developed at a critical length scale of matter typically under 100 nm. (after National Science and Engineering Technology Council NSET, Feb 2000, www.nsf.gov/crssprgm/nano/reports/omb_nifty50.j sp) 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. ► 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 Thin Film Deposition Techniques (Materials and Processing Technology), by Krishna Seshan, (Noyes Publications 2002) ► Handbook of Plasma Immersion Ion Implantation and Deposition, Wiley 2000 ► Handbook of Nanotechnology (Springer 2010), B. Bushan FC250 Nano-and microtechnologies: 1.1 Fields of Expertise, Suggested Literature Lenka Zajíčková 6/37 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 FC250 Nano-and microtechnologies: 1.1 Fields of Expertise, Suggested Literature Lenka Zajíčková 7/37 ► 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 FC250 Nano- and microtechnologies: 1.1 Fields of Expertise, Suggested Literature Lenka Zajíčková 8/37 Scientific Papers 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 FC250 Nano- and microtechnologies: 1.1 Fields of Expertise, Suggested Literature Len ka Zajickovä 9/37 Related courses ► F7360 Characterization of surfaces and thin films (in English, spring semester 2018) ► FB100 Plasmachemical processes (in English, fall semester) ► F3390 Micro- and nano-structures preparation (spring semester) ► F4280 Thin Films Deposition and Surface Modification Technologies (spring semester) FC250 Nano- and microtechnologies: .2 Approaches in Micro/Nanotechnologies ka Zajíčková 10/37 1.2 Approaches in Micro/Nanotechnologies FC250 Nano- and microtechnologies: 1.2 Approaches in Micro/Nanotechnologies Lenka Zajíčková 11 / 37 1.2 Approaches in Micro/Nanofabrication 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) ► preparation of surfaces (cleaning, polishing, functionalization) Lithography bottom-up ► building using nanoobjects (atoms, molecules), self-assemply of structures ;om-Up Top-Dow Synthetic Chemistry, Genetic Engineering,... FC250 Nano- and microtechnologies: Overview of Top-Down Fabrication ka Zajíčková 12/37 1.3 Overview of Top-Down Fabrication ► Lithography ► Etching/Sputtering Processes ► Preparation of Films ► Doping ► Surface Treatment FC250 Nano- and microtechnologies: 1.3 Overview of Top-Down Fabrication Lenka Zajíčková 13/37 Basics of Lithography 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 Tbl oft Substrate Pholoies ist coat tag & development Photo its ist ashing plasma lithography patterning with positive resist FC250 Nano- and microtechnologies: 1.3 Overview of Top-Down Fabrication Lenka Zajíčková 14/37 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 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) Several aspects have to be taken into account: ► functional properties of the deposition ► uniformity of the processes ► step coverage conformality ► reproducibility ► simplicity ► price ► etc. FC250 Nano- and microtechnologies: 1.3 Overview of Top-Down Fabrication Lenka Zajíčková 16/37 Thin-Film Process S 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). FC250 Nano- and microtechnologies: 1.3 Overview of Top-Down Fabrication Lenka Zajíčková 17/37 Thin-Film Process S Steps 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! FC250 Nano- and microtechnologies: Overview of Top-Down Fabrication ka Zajíčková 18/37 ... process of introducing impurity atoms into a semiconductor region in a controllable manner in order to define the electrical properties of this region. ► All electronic and optical semiconductor devices incorporate dopants as a crucial ingredient of their device structure. ► The doping with donors and acceptors allows to modify the electron and hole concentrations in Si in a very large range from 1013cm-3 up to 1021 cm-3. ► The carrier concentration can also be varied spatially quite accurately which is used to produce pn-junctions and built-in electric fields. n-doped silicon p-doped silicon 'miss i ^electron Periodic Table of the Elements H IIA III A 3A IVA 4A VA 5A 6A V IIA 7A 2 He LI at Be S ib 6 C 7 N ' on S JL 1ü Ne Via SS. ä 3 Die 3B IVB 1B 5 VB 5B e VIB GB VDB 7B 8 9 — VIII— a 10 ii IB 1B 12 IIB 2B 13 Al_ "Si 16 P 16 S "ci_ "Ar I" _ K 'skat 21 Sc 22 Ti V "Cr 2E Mn 26 Fe 1 IBLHft Co Ni 28 Cu 30 Zn Ga 32 Ge As 14 Se 35 Br 36 Kr 3Rb 40 Zr 41 Nb 42 Mo Jc 44 Ru 45 Rh 46 Pd 47 48 Cd 49 In 50 Sn Sb 12 Je 53 1 54 Xe 55 _ Cs SSs. 56 Ba 57-71 72 Hf 73 Ta 74 W 75 Re Os Ir 78 Pt , MM Au 80 ho 81 TI 82 Pb 83 i 14 Po 85 At es Rn 87 "ka 39-103 104 .51. 10S Db 106 Sg 107 Bh 108 hb 109 _Mt Ds Rg 112 rCn_ 113 114 IIS Uut Uuq Uup 116 Uuh Üus Uuo Series B7 68 La Ce Ba , Pr 60 Nd 61 62 Pm Sm 63 Eu 64 Gd 65 Tb 66 67 Dy Ho as Er 69 Tm 70 71 Yb Lu A ethics Sari as B9 90 Ac Th SS. SSB 01 _ Pa 92 93 94 Np Pu SG Am SE Cm 97 Bk 9S 99 Cf_ _Es_ 100 Fm 101 Md 102 103 No Lr FC250 Nano- and micro-technologies: urtace I reatmen Overview of Top-Down Fabrication 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 FC250 Nano- and microtechnologies: 1.4 Plasma Technologies Lenka Zajíčková 20 / 37 1.4 Plasma Technologies FC250 Nano- and micro-technologies: 1.4 Plasma Technologies Lenka Zajíčková 21 12,7 Unique Features of Plasma Technologies 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) Plasma processing: ► is a dry process, i.e. with low consumption of chemicals, ► provides combined effect of physical processes (ions, UV photons), chemistry (radicals, excited species) ► offers replacement of toxic and explosive reactants ► enables preparation of new materials FC250 Nano- and micro-technologies: 1.4 Plasma Technologies Lenka Zajíčková 22/37 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 FC250 Nano- and micro-technologies: 1.4 Plasma Technologies Lenka Zajíčková 23/37 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 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 FC250 Nano- and micro-technologies: 1.5 Examples of Bottom-Up Fabrication ka Zajíčková 24/37 1.5 Examples of Bottom-Up Fabrication FC250 Nano- and micro-technologies: 1.5 Examples of Bottom-Up Fabrication Len ka Zajíčková 25/37 Carbon-Based Nanomaterials - formed by sp^C sp2-C bonding (one valence electron in pure p state and the other three in hybrid orbitals) enables synthesis of several interesting carbon nanomaterials due to planar bond structure Formation of 3 sp2 hybrid orbitals: combination of 1 /3s and 2/3p - trigonal planar bonding directions with angles of 120° unhybridized p orbital Copyright 199fl by John Wiley and &sna Ire. All nqhts nasarved. FC250 Nano- and microtechnologies: 1.5 Examples of Bottom-Up Fabrication Lenka Zajíčková 26 / 37 .HOOH. .... Different chirality of SWNT: - prepared 1991 by hjima 3 (a) armchair (b) zigzag (c) chiral (n,m) FC250 Nano- and micro-technologies: 1.5 Examples of Bottom-Up Fabrication Lenka Zajíčková 27/37 Growth of Carbon Nanotubes Widely-accepted growth mechanisms for CNTs: (a) tip-growth model, (b) base-growth model. (a) (b) Metal Substrate JL Growth stops (i) (ii) m*.i^ — ^ tV]X-'Mlh~,T1~:1T 2. Etch oxid e for pMQSFET p-type substrate 3. Diffuse n-well ox.- p-type OLibstJčits In-well J 4. Etch oxide for nMOSFET l>-tyi5eiiih5tič(te ^ji-well J 5. Grow gate oxide ZD_ iMYiJeiubstiďte 6. Deposit polysiicon ^-^=0= p-type SLibstJčitŕ In-well J 7. Etch polysilicon and oxide °*n i i ■==■ r~~ p-typesubstrabe - 8. Implant sources and drahs . „ .. Wwell J p-typesuhstrete - 9. Grow nitride r=i i i f=i r~ p-type substrate 10. Etďi nitride p-type substrate ii-well_J 11. Deposit metal p-type substrate 12. Etch metal p-type su b strate FC250 Nano- and micro-technologies: 1.5 Fabrication of micro-and nanodevices Lenka Zajíčková 33/37 Back-end-of-line (BEOL) Structure Legend: SEM view of three levels of copper interconnect metallization in IBM's CMOS integrated circuits (Photograph courtesy of IBM Corp., 1997) FC250 Nano- and microtechnologies: 1.5 Fabrication of micro- and nanodevices Lenka Zajíčková 34/37 Technology Nodes in Microelectronics Technology node - process sequence for manufacturing a chip Marketing Takes Over Engineering Definitions Drawn gate length Ldiawn ~ Width specified by layout engineer Actual gate length Laclua| Actual physical width of gate material Effective gate length LEffe(.t|V(, ~ Over etch shortens physical width of gate Effective gate length Leffative ~ Dopant migration shortens effective gate length Actual Gate Length Pitch Counts Year Node Half-pitch Gate length* 2009* 32 52 23 2007» 45 6fl 33 2005* 65 90 32 90 90 37 100 100 45 zrjDic 130 150 65 mv* ISO ?3D 140 1997«* 250 250 200 1995 ^ 350 35P 350 1992 d 500 500 500 ♦ HeftsMewldlhlsdelined as1hephySi 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. FC250 Nano- and microtechnologies: 1.5 Fabrication of micro- and nanodevices Lenka Zajíčková 36/37 Dimensions of MEMS/NEMS in Perspective MEMS: C harac Istí l Líc ler^Lh leu lhan 1 rnrn, larger than 100 urn N EM 5: Lsll Lhari 1 00 nm C aLom 0.1 ů urn 0.1 DM D 12 fim Q uari Lurn-do L LrarisiiLor 300rim Red blood cell S fim Molecular gear lOnm-lOOTum 1 5WCNT Lrantitlor DNA 2.5n rn 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) FC250 Nano- and micro-technologies: 1.5 Fabrication of micro- and nanodevices Lenka Zajíčková 37/37 Examples of MEMS - gears/motors ***zrw&&**^ zkum ^- 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.) 1,