Plasma and Dry Micro/Nanotechnologies 4. Deposition Lenka Zajíčková Faculty of Science, Masaryk University, Brno & Central European Institute of Technology - CEITEC lenkaz@physics.muni.cz spring semester 2023 Central European Institute of Technology BRNO I CZECH REPUBLIC rit 4. Deposition 4.1 Introduction to Deposition 4.2 Adsorption 4.3 Surface Diffusion 4.4 Nucleation 4.5 Structure Development 4.6 Thin-Film Deposition Process Steps 4.7 Overview of Deposition Methods Deposition may be considered as six sequential substeps: 1. Adsorption of arriving atoms and molecules on the surface. 2. Diffusion before becoming incorporated into the film. 3. Reaction of adsorbed species with each other and the surface to form the bonds of the film material. 4. Initial aggregation of the film material - nucleation. 5. Development of a structure (morphology) as the film grows thicker. It includes topography (roughness) and crystallography. 6. Diffusional interactions within the bulk of the film and with the substrate Surface Reactions Deposition Deposition j J Downward Desorption Plasma & Dry Technologies Deposition ka Zajíčková 4/40 Consider a molecule approaching a surface from the vapor phase. ► A few atomic distances from the surface molecule begins to feel an attraction -interaction with the surface molecules by van der Waals forces (London dispersion forces): ► molecules/atoms without dipole moments (symmetrical or intert) interact due to oscillating dipoles, i.e. induced-dipole interaction ► polar molecules (permanent dipoles) interact more strongly ► The approaching molecule is being attracted into a potential well - accelerates down the curve until it passes the bottom and is repelled by steeply rising potential. 6 Strong Intermediate Weak Graphene+TMA 2 2 3 4 Distance (a.u.) An illustrative Lennard-Jones potential model for physical adsorption. ► If enough of the molecule's perpendicular component of momentum is dissipated into the surface the molecule cannot escape the well after being repelled =^ physisorption ► fraction of physisorbed molecules - trapping probability S ► reflected 1 — 5 ► S is different from thermal accomodation coefficient 7 introduced previously ► molecule is at least partially accomodated thermally to the surface temperature Ts even when it is reflected ► The physisorbed molecule is mobile on the surface except at cryogenic T - hopping (diffusing) between surface atomic sites. vapor molecule reflection desorption 3 utilization H a incorporation physisorption chemisorption During surface diffusion the molecule ► may desorb after a while by gaining enough energy in the tail of the thermal energy distribution. ► may undergo a further interaction consisting of the formation of chemical bonds with the surface atoms, i.e. chemisorption. The chemisorption reaction probability £ is used in the case of chemisorption on a foreign substrate instead of condensation coefficient ac. ► some of adsorbed species eventually escape back into the vapor phase =^ sticking coefficient Sc - fraction of the arriving vapor that remains adsorbed for the duration of the experiment. vapor molecule reflection desorption T / / 3 utilization n a incorporation physisorption chemisorption ► Sticking coefficient Sc has less fundamental meaning than 5 and £ (or ac) that are determined solely by chemistry and energy. Nevertheless, Sc is very useful in thin film deposition - it is the fraction of arriving vapor incorporated into the film (buried before escaping). ► Utilization fraction 77 of a chemical vapor - fraction of molecules utilized for the deposition =^ r\ can approach unity even when Sc is very low. vapor molecule reflection desorption 3 utilization n a incorporation physisorption chemisorption Chemisorption - sharing electrons, physisorption - dipole interaction. If both adsorption states exist, the physisorption is called precursor state. The precursor model may also be applied to cases where both the adsorption states involve chemical bonding but one is weaker. The precursor model has long been applied to heterogeneous catalysis, thin-film deposition and condensation of molecular vapors. Recent theory indicates that even the condensation of monoatomic vapor such as Al can involve both adsorption states: the precursor state = AI-AI dimer with limited bonding to bulk Al. ► In most CVD reactions, the feed vapors adsorb as molecules that undergo reaction breaking their molecular bonds and form new bonds to surface ► In deposition of compounds from separate vapor sources of each element, adsorbing vapor bonds much more strongly to surface sites occupied by the other element ► Si chemically passivated by H reacts with adsorbates mainly at those few sites that are missing H atom. On the H-passivated sites, adsorbates remain only physisorbed. ► Atomically flat surfaces often bond more strongly with adsorbates at atomic steps. SiH4(g) ----> SiH4(a) Si(c) + 2H2(g) (1) Zn(g) + Se(a) —)• ZnSe(c) and Se(g) + Zn(a) —)• ZnSe(c) (2) Consider hypothetical diatomic gas-phase molecules chemisorbing as two Y atoms: 2Y(g) dissociative chemisorption Y2(q) adsorbing and then dissociative Lifting atomic Y out of its potential well along curve c results in much higher molar potential energy Ep in the gas phase - roughly the heat of formation, AfH, of 2Y(g) from v2(g). The curve a represents activated chemisorption - there is an activation energy Ea to be overcome for Y2{g) to become dissociatively chemisorbed. For deeper precursor well, curve b, chemisorption is not activated though there is still a barrier Erb. Plasma & Dry Technologies 4. Deposition ka Zajíčková 10/40 ► In curve c, Ep is high enough =>* direct chemisorption (without involving precursor state) =>• Eley-Rideal mechanism, i.e. direct reaction between an incoming species and a surface site ► Langmuir-Hinshelwood mechanisms: (i) adsorption from the gas phase, (ii) dissociation of molecules at the surface (iii) reaction among surface species (chemisorbed molecules) +400 - -600 L- of Y2(g) * * „ ■ ■ precursor physisorption dissociative chemisorption Two ways in which vapor can arrive at surface having Ep > 0: ► Gaseous molecules have their Ep raised by becoming dissociated. Solids and liquids have it raised by evaporating. Energy-enhanced deposition processes provide enough energy Ep > Ea ► sputter deposition - arriving species have kinetic energy ~ lOOOkJ/mol and Ep > 0. ► plasma-enhanced deposition - vapor molecules are dissociated in plasma Plasma & Dry Technologies 4. Deposition Lenka Zajíčková 11/40 Thermally controlled deposition In evaporation and CVD, the vapors often adsorb first into the precursor state (curve a, b) ► and chemisorb by overcoming the barrier Er(a,b) ► or desorb by overcoming the heat of physisorption Edrahy these two reactions result in a net rate of chemisorption. First-order chemical reaction Rk = kkns = kkns0Q (3) Rk rate of /cth surface reaction per unit area [m_2s_1] kk rate constant [s_1] ns surface concentration of reactant [m-2] 0 fractional surface coverage by reactant with rate constant following Arrhenius equation: kk "ok exp(--^) u0k frequency factor or pre-exponential factor Ek reaction activation energy [kJ/mol] (4) mass balance for the physisorbed precursor: assuming ns is constant over time (steady state), chemisorption reaction occurs only in the forward direction (not valid for too high T at which film begins to decompose), adsorption occurs on free sites - 0) = Rr + Rd = (kr + kd)ns0G (5) l~i molecular impingement flux [m_^s_1], 5 trapping probability Rr reaction (chemisorption) rate and Rd desorption rate Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 12/40 Sticking Coefficient Using previous relations we obtain for surface coverage 0 0 ^jS/ns0 t~iS/nso + kr + kd and substituing into the chemisorption rate expression (3) V{5kr (6) Rr = krns0Q = t~iS/nso + kr + kd We may now define sticking coefficient Sc more precisely Sc = Rr/V{ In case of small ri5 i.e. small 0 Eq. (7) simplifies to V{5 _ 6 (7) (8) R r = 1 + kd/kr = l~i 1 + "0d "Or exp( Er Ed ) (9) where £ is chemisorption reaction probability. Sc « £ for 0 < 1 but for larger 0, Sc < £. For the special case of film deposition from single vapor having the same composition as the film, £ = ac (condensation coefficient). The assumption of 1st order kinetics is not always valid for a more complicated case of compound-film deposition from multicomponent vapors. For more details refer to book of Donald Smith, chapter 7.3.3. Plasma & Dry Technologies Deposition ka Zajíčková 13/40 Activated adsorptio The ► ► +400 - chemisorption rate Rr governs the rate of film deposition when kr is the same from site to site along the surface Ts is not so high that decomposition or re-evaporation of the film occur. of Y2(g) -600 * * - ■ ■ precursor physisorption dissociative chemisorption Rr = l~i 1 + u0r eXPV RTS ) If Er Ed there is an activation energy Ea = Era - Eda for chemisorption (curve a). For high Ea the film fail to deposit unless 7"s is raised to make exp. term smaller => Rr t for T t The activated case is very common in CVD. If Er : Ed (chemisorption is not activated as in curve b) Rr I for T t Example: Si deposits from SiH4 at elevated (not room) Ts. If 7"s becomes too high, the Si evaporation flux > Rr and deposition stops. The net deposition flux of Si: V r — Rr — (10) Ts window for deposition. Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 14/40 4.3 Surface Diffusion typical kJ/mol 4M U 400 (o) Site 1 phyaiaorption transition aute aite 2 chemiaorption Flux of adsorbate rs [m~1s~1] across the Es barrier between 1 and 2 sites in the x direction Rate of barrier crossing Rs R,= -^ (11) (a is the distance between the sites) Considering Maxwell-Boltzmann distribution 1 nsv Rs= - — 4 a n f _s a kBT 27T/T? (12) n's - surface concentration of adsorbate residing in the transition state. Relation between nfs and r?s? - from statistical physics (next page) Arrhenius law for Rs Plasma & Dry Technologies Deposition ka Zajíčková 15/40 oncentrations in Surface States Relation between n's (concentration in transition states) and ns (concentration in adsorption states)? Z = ^>,e y*r) (13) /7 We-(£) ns ZrZvZt Z - partition function, g,- degeneracy of the energy level, r, v, t rotational, vibrational, translation kinetic energies (electronic excitations are neglected at ordinary T), The Boltzmann factor accounts for the potential energy difference Es (J/mol) between the adsorption-site state ns and the transition state n's ► rotation of molecules is limited by adsorption =^ Z'r = Zr = 1 ► Zvk derived from quantum mechanics for harmonic oscillator ZVk = 1 but vibrational modes are mostly in their ground states at ordinary T ► partition function for translation energy h (14) (15) n's = ns-4exP-(-^:) (16) Plasma & Dry Technologies 4. Deposition Lenka Zajíčková 16/40 Rate of barrier crossing Rs, molecular hopping rate ks ... using absolute-reaction-rate theory (predicts the absolute reaction rate of a chemical reaction from the quantum mechanical description of the potential energy changes during the interaction; cannot provide a quantitative estimation of the diffusion rate but gives an insight into the determining factors) Rs = ns[ -^j-) exp(--^) fis^osexp(--^:) nsks (17) Arhenius expression for the rate constant ks of "chemical reaction". The rate constant ks (s_1) represents the frequency with which an individual adsorbate molecules "hops" to an adjacent site. Thus, the factor u0s = 1013 - 1016 s_1 is NOT the frequency of any vibrational component vk of the adsorbate. The rate of surface diffusion increases exponentially with t T and I Es (activation energy for surface diffusion). Es < Ed, Ec (desorption activation energy of physisorbed or chemisorbed species, respectively) =^ high rate of surface diffusion at film deposition T approaching the onset of re-evaporation, i. e. when exp(— j^) becoming significant = one of principal ways in which substrate T affects film structure. Es/Ec sometimes referred as corrugation ratio, it is lower for metals than for semiconductors due to absence of bond directionality in metals. Plasma & Dry Technologies Deposition ka Zajíčková 17/40 i iTTusion Le Relation between molecular hopping rate ks and the distance which an adsorbate molecule travels during the film deposition: ► classic random-walk problem ► The final locations are more widely dispersed from the starting point with increasing 2 time t. For large number of hops N0, it is Gaussian dispersion exp(—^) characterized by its standard deviation a - here the diffusion length A A = r^/No « a^/No = ay/kTt r is per-hop rms change in the distance from the starting points How A depends on temperature? Two regimes need to be considered separately: ► t is time between adsorption and burial by the next depositing monolayer ► adsorbate is more likely to desorb than to be buried within t Regime 1 - burial time: t = no A = a, ^os^O / Es x -exp (--——) Tr HV 2RTJ where n0 is surface density of adsorption sites (m-^), rr deposition flux (m_2s_1) and ks — Vos exp(-|^) Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 18/40 Diffusion Length - contin. Regime 2- If T is high enough the film re-evaporation (desorption) becomes significant. =^ t is adsorption lifetime. Considering the desoprtion only from chemisorbed state (negligible concentration of precursor state at high 7~): 1 kr U 1 ,Ec exp( —) OC where subscript c denotes the chemisorbed state. Combining both gives A = a ^os / Ec Es exp ( ) z/ OC 2R7 (1 In increased J, 1/T Plasma & Dry Technologies Lenka Zajíčková How is the diffusion length A (obtained from the examination of motion of individual adsorbed molecules) related to the macroscopic quantity - diffusion coefficient? Transport equation 1% = —D dA7s dx l~s, ns have surface units m 1s 1 and m 2 Using analogy to 3D case D = ± vavX, in which the mean free path A is the hop distance a, and the mean speed vav is ksa D=-ksa2 => A = aVfeř = 2^Ďi 4 (19) Thus, we can express D in the Arrhenius form when using this expression for ks D= l^oSa2exp(--|^) = D0exp(— (20) Plasma & Dry Technologies 4. Deposition Len ka Zajíčková 20 / 40 4.4 Nucleation Nucleation is a complication that must often be added to the above described model of chemisorption where we expected that kr is the same from site to site. If nucleation is important, the net deposition flux rr = Rr — f~v is Vr > 0 only for certain active substrate-surface sites, nucleation sites or nuclei of film material which have spontaneously accumulated. Various examples: ► Si chemically passivated by H reacts with adsorbates mainly at those few sites that are missing H atom =^ Rr t at unpassivated Si surface atoms because of I Er ► In deposition of compounds from separate vapor sources of each element, adsorbing vapor bonds much more strongly to surface sites occupied by the other element Zn(g) + Se(a) —)• ZnSe(c) and Se(g) + Zn(a) —)• ZnSe(c) ► atoms of low-reactivity metals often bond much less easily to nonmetallic substrates: Ea of chemical bond of Zn, Cd to glass is very high because of high bond strength between substrate elements =^ Zn, Cd on glass bonds more readily to itself than to the surface =^ formation of nucleus The existence of certain sites which are active in adsorption is common in thin-film processes. Access of precursor to these favored sites can dominate the deposition kinetics. Two types of access ► from vapor phase - Eley-Rideal mechanism ► by surface diffusion - Langmuir-Hinshelwood mechanisms Plasma & Dry Technologies Deposition ka Zajíčková 21 /40 urrace tension 7 ana surrace tree e Concept of surface tension 7 has to be introduced to understand nucleation. The force F required to draw a liquid membrane: F = 2^7 (b is circumference, 2 stands for inner and outer surface). Work FAx to create the membrane of area A = 2bAx is stored as surface energy surface energy per unit area FAx/A -- 7 [N/m] =>- For liquids, surface (free) energy per unit area (J/m2) is equal to surface tension 7. For solids at T > 0 K, the surface Gibbs free energy is reduced by entropy factor G = H — TS which depends on the degree of surface disorder =^ surf, energy is minimized by surface diffusion. In solids, there is an surface energy term A J^- cr,yd£,y in which cr,y is surface stress and de,j surface strain tensor deySy ■- - dA/A. Liquids cannot support such strain because the atoms just rearrange to relax it. Plasma & Dry Technologies 4. Deposition Len ka Zajíčková 22 / 40 Thin-film growt h Nature tends to minimize surface energy 7A ► when wire is lifted far enough, the membrane is in the plane of the ring ► in solids, surface energy minimizes by surface diffusion fundamental process to development of structure in thin films In thin-film growth, both A and 7 are varying: ► A depends on surface topography ► 7 depends on many properties of exposed surface (chemical composition, crystallographic orientation, atomic reconstruction, atomic-scale roughness etc.). It is anisotropic for most crystalline solids. For deposition onto a foreign substrate, nucleation behaviour is strongly influenced by surface tension of substrate, 7S. We also need to consider 71 of the substrate-film interface and 7f of film free surface. Two cases for growth modes: ► A > a, i. e. deposition material can rearrange itself to minimize 7, nucleation is not kinetically limited and approaches equilibrium ► A < a atoms sticks where they land and the growth behaviour is "quenched" For A > a, there are two nucleation situations on the bare substrate ► (a) films wets the substrate because 7f + 71 < 7S =>* smooth growth, atomic layer by layer (Frank-van der Merwe growth). It requires strong enough bonding between film and substrate to reduce 71 ► (b) with insufficient substrate bonding film forms 3D islands (Volmer-Weber growth mode). In extreme case of no bonding at all 71 = 7f + 7S, the film spreading across the substrate would increase the total surface energy by 2^. (a) (6) (O Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 24/40 Growth Modes for A > a (contin.) Third growth mode, Stranski-Krastanov, shown in (c) - growth mode changes from layer to island after a monolayer or two due to a change in the energy situation. s f \ r try*? * t if f^řfřj (a) (b) (c) 3D nucleation is usually undesirable since it leads to rough, nonuniform films (extreme example being the diamond nuclei) How to manipulated with the growth mode? Film wetting for 7f + 71 < 7S- 7i decreases with film-substrate bonding (covalent, ionic, metallic). In general, interfacial bonding is stronger between materials having the same type of bonding. Examples: chemically-active metal, Cr, will bond to glass by breaking Si-0 bond and forming Cr-0 ► Au cannot do this, i.e. does not bond well to glass ► Au forms a strong metallic bond to clean Cr Using intermediate "glue" layer (Cr) which bonds well to both, the film and the substrate, 7/ can be reduced and wetting accomplished. Another good bonding material is Ti. Alternatively, energy-enhanced techniques (plasma treatment, ion bombardment, sputtering) can provide the activation energy for bonding between film and substrate, i.e. reduce 7,. Plasma & Dry Technologies Deposition ka Zajíčková 26 / 40 nucieation -1 two cases Two ways in which 3D nuclei can form ► bonding initiates at active surface sites such as atomic steps, crystal deffects, impurities. At these nucieation sites, the Ea is lower than elsewhere. ► even if there are no active nucieation sites, 3D nuclei can still form at random surface locations because of the interfacial bonding which develops by the spontaneous accumulation of mobile atoms plus arriving vapor into "critical" nuclei which are big enough to be stable (classical nucieation problem) Plasma & Dry Technologies 4. Deposition Lenka Zajíčková 27/40 3D nucleation - how to produce smooth & uniform film? ► concentration of critical nuclei n* has to be t ► and their radius r* I, i.e., less coarse nucleation How to achieve it? ► Using very high vapor arrival rate (supersaturation), at least until the nucleation phase is over and the film is continuous. Coarsening will still occur even with one-atom critical nuclei because atoms and nuclei are mobile on the surface migration and coalescence ► Decrease the substrate T to inhibit surface diffusion freezing the nucleation and coalescence. If arriving species do no thave enough energy to desorb or diffuse they remain where they land - quenched growth mentioned earlier. In this case, the nucleation is kinetically inhibited by the surface-diffusion activation-energy barrier Es Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 28/40 4.5 Structure Development Upon coalescence of the surface nuclei to form a continuous film, the nucleation step of the film deposition is complete and 4th step begins - development of the bulk film structure. The form of the structure changes dramatically with ► the amount of thermal motion taking place during film growth: scales with Ts/Tm (melting point of the film over substrate temperature - in K) - known as homologous or reduced T the amount of additional energy being delivered to the growth surface H.utjHl.rFiU: Figure 6,16 Characteristics of the four basic structural zones and of whiskery in eras section, The ratio of substrate T to film melting T Cr/T^") increases in the direction Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 29/40 4.5 Structure Development quenched growth for Z1 and ZT: ► Z1 occurs at 7"s/7m so low that surface diffusion is negligible, i. e. A < a. Z1 consits of columns typically tens of nm in diameter separated by voids a few nm across. The columns have poor crystallinity (many deffects) or are amorphous. In thicker films, an array of cones with wider voids between them become superimposed upon this structure. The cones terminate in domes at the surface, and the size of the domes increases with film thickness. ► ZT also occurs when A < a. It contains defected columns as Z1 but the voids and domes are absent. ZT is usually associated with energy-enhanced processes. subuLríilL: nguni &15 Characteristics of the fcui basic structural zones and of whislteTa, in croas section, The ratio of substrate T to film melting T Cr/T^j increases in the direction Z1-*ZT-»Z2->Z3- Plasma & Dry Technologies 4. Depositi ion Lenka Zajíčková 30/40 4.5 Structure Development thermally activated rearrangement on or within the film for Z2 and Z3: ► Z2 occurs for Ts/Tm > 0.3, diffusion becomes significant. It consits of columns having tight grain boundaries between them and having a characteristic diameter which increases with 7"S/Tm. Crystalline columns are less defected than in Z1 and ZT, and are often facetted at the surface. The Z2 structure can also accur in amorphous films. The column boundaries are planes of reduced bonding rather than planes of crystallographic discontinuity. ► Z3 occurs at certain instances at 7"S/Tm > 0.5, considerable bulk annealing of the film is taking place durina deposition, more isotropic crystallite shapes. KubuLrfilL: Figuns &1S Characteristics of the four basic structural zones and of whiskers, in croas section, The ratio of substrate T to film melting T CTyTra) increases in the direction Z1-*ZT-»Z2->Z3- Simple model of statistical roughnening caused by statistical fluctuation in the vapor arrival flux: each atom is constrained to stick on the site it lands on (even if it is on top of a pillar) For large enough N (average number of atoms per depositing site) the variation in heights is described by Gaussian distribution with standard deviation a = a\/Kl = \fah where h = aN is average film thickness Note: analogy to dispersion in lateral direction arising from surface diffusion because both are random processes Figure 5.16 Statistical roughening in random ballistic deposition of a 25-atom-thiek film. (Pascal solution courtesy of Jansd Smith-Mickeluon.) Plasma & Dry Technologies Deposition encnea g ka Zajíčková 32/40 (a) |Ah| Aj|Ah| id) ■v. Atomistic processes in quenched-growth structure development (more realistic model): (a) ballistic aggregation (arriving atoms cannot perch on top of each other but rather settle sideways) ► (b) effect of atoms finite size (shadowing low areas) (c) sideways attraction (development of columns) ► (d) oblique shadowing (self-shadowing, incidence over range of 0 occurs for fluid-flow regime Kir?< 1) ► (e) tilt effect ► (f) low sticking coefficient ► (g) void-filling by energetic particle due to enhanced mobility (left) and forward sputtering (right) 'f. if) 2D MD simulation of the deposition of energetic atoms impinging perpendicularly onto a substrate held at 0 K. The horizontal line is substrate interface. Et/Ec = incident energy / adatom potential-well depth ► (a) Et/Ec = 0.02 ► (b) Et/Ec = 0.5 ► {c) Et/Ec = 1.5 Plasma & Dry Technologies Deposition ka Zajíčková 34/40 Rgure 5£0 Twtj-dimeruiional computer simulation of the effect af iubitrat* T on void filling by Btirtact diffusion. (Sonn«: Reprinted from Kef. 22 ty parmissionj Plasma & Dry Technologies Deposition ka Zajíčková 35/40 cess 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). Plasma & Dry Technologies 4. Deposition Lenka Zajíčková 36 / 40 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! Plasma & Dry Technologies Deposition ka Zajíčková 37 / 40 4.7 Overview of Deposition 1 M let hod 1 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 Plasma & Dry Technologies 4. Deposition Lenka Zajíčková 38/40 Overview of Deposition Methods I - evaporative methods vacuum evaporation Coaling c.ir;iLL-.:l ;itnni íegftssiříi; írom Lit hcsietl cojifiLVcioiifl pulsed laser deposition Power supply to heater Vacuum Chamber vacuum evaporation (resistive and electron beam "KZZZZZZ Source Sub&trale * r Varmint Evaporation 3utiilratfl J Electron Beam Rource Vacuum Resistive Healing n * r V ion-beam assisted deposition (IBAD) Component (s) e-beam Evaporator Rotating Substrate Holder a Monitor Energetic Ion Source Vacuum Chamber dual ion-beam deposition ■"■■J IrtJi"i ! .-ľ :;■ --in i