MODELING ELECTRONEGATIVE PROCESSES IN PLASMAS*

Transcription

1 MODELING ELECTRONEGATIVE PROCESSES IN PLASMAS* Pof. Mak J. Kushne Unvesty of Illnos 1406 W. Geen St. Ubana, IL USA Septembe 003 * Wok suppoted by the Natonal Scence Foundaton Semconducto Reseach Cop and 3M Inc, NEGPLASMA_0903_01

2 AGENDA Physcs of electonegatve plasmas What s dffeent? Modelng stateges fo electonegatve plasmas. Examples fom low pessue systems Examples fom hgh pessue systems Concludng emaks NEGPLASMA_0903_0 Unvesty of Illnos Optcal and Dschage Physcs

3 MODELING ELECTRONEGATIVE PLASMAS Ths could be a vey shot talk.. Thee s nothng fundamentally dffeent about modelng electonegatve plasmas fom electopostve plasmas. You ust need to account fo all the physcs.. The bette you awaeness of the physcs, the moe accuate you model wll be. Howeve.. NEGPLASMA_0903_03 Unvesty of Illnos Optcal and Dschage Physcs

4 MODELING ELECTRONEGATIVE PLASMAS Modelng electonegatve plasmas s all about plasma chemsty. To some degee, all electopostve plasmas look alke. To model electonegatve plasmas well, one must addess the unque molecula physcs of you feedstock gases, the fagments and poducts. Ths s what we also call physcal chemsty; the physcs of bonds n molecules. The bette you awaeness of the physcal chemsty, the moe accuate you model wll be. Let's begn wth how the bonds n molecules detemne you negatve on plasma chemsty. NEGPLASMA_0903_03A Unvesty of Illnos Optcal and Dschage Physcs

5 DISSOCIATIVE ATTACHMENT The maoty of negatve ons fomed n low pessue plasmas ae by dssocatve exctaton of molecula speces. e AB A B- ε = electon theshold enegy T = knetc enegy of fagments EA(B) = Electon affnty of B Potental Enegy U(R) ε The molecule s excted to ethe a eal o vtual state whch has a cuve cossng wth a dssocatve state. The fagments may be poduce wth sgnfcant knetc enegy. e o Dssocatve State Bound State AB A B A B - EA(B) Intanuclea Sepaaton (R) NEGPLASMA_0903_04 Unvesty of Illnos Optcal and Dschage Physcs

6 THERMAL DISSOCIATIVE ATTACHMENT If the dssocatve cuve cuts though the bottom of the bound state potental well (= o ), electons of zeo enegy can ntate the dssocatve attachment. Example: e Cl Cl Cl- NEGPLASMA_0903_05 Ref: Chstophoou, J. Phys. Chem. Ref. Data 8, 131 (1999) Unvesty of Illnos Optcal and Dschage Physcs

7 INELASTIC DISSOCIATIVE ATTACHMENT Dssocatve cuve ntesects potental well at > o. Consevaton of momentum ( =0) esults n a fnte theshold enegy. Example: e CF 4 F-, CF 3 -, F - Potental Enegy U(R) CF4 e Dssocatve States CF3 F CF3 - F CF F - CF3 F - o Intanuclea Sepaaton (R) NEGPLASMA_0903_06 Ref: Chstophoou, J. Phys. Chem. Ref. Data 5, 1341 (1996) Unvesty of Illnos Optcal and Dschage Physcs

8 3-BODY NON-DISSOCIATIVE ATTACHMENT When the attachment s non-dssocatve (e.g., e O O -) a 3 d body s usually equed to dsspate the momentum of the ncomng electon. The actual attachment pocess s a sees of 1 st and nd ode events. e O ( O ) * k1 ( O ) τ e O * Attachment Autodetachment ( ) * k O M O M Stablzaton NEGPLASMA_0903_07 Unvesty of Illnos Optcal and Dschage Physcs

9 3-BODY ATTACHMENT: EFFECTIVE -BODY RATE The effectve two body ate coeffcent demonstates the low pessue egme whee stablzaton s slow; and the hgh pessue lmt whee autodetachment s not mpotant. d [( ) ] * O = [][ e O ] k ( O ) [( ) ] * [][ e O ] O d [ O ] = ( O ) dt dt k' = 1 k 1 Mk τ [ ] * [ ] [][ ] [( ) ] * e O k1mk * Mk O [][ e O ] k1 1 Mkτ Mk τ 1 Mk τ 0 k' NEGPLASMA_0903_08 Unvesty of Illnos Optcal and Dschage Physcs

10 3-BODY ATTACHMENT: EFFECTIVE -BODY RATE k1 Hgh Pessue Lmt O : k 1 = 3 x cm 3 s -1, τ = 0.1 ns, k 5 x cm 3 s -1 Hgh pessue lmt eached at 4 atm k (-body) Mk >> 1/τ (Collsonal stablzaton domnates) Fall-off Regme (Autodeatchment domnates) Almost always acceptable to use 3-body ate coeffcent k3 e O M k 3 k 1 k O τ.3 10 M 30 cm 6 s 1 Pessue Fo (C 4 F 8- )*, τ = 1 µs, and the hgh pessue lmt s at 0.3 To. NEGPLASMA_0903_09 Itkawa, J. Phys. Chem. Ref. Data 18, 3 (1989) I. Saues, J. Chem. Phys. 71, 3016 (1979). R. L. Woodn, J. Chem. Phys. 7, 43 (1980). Unvesty of Illnos Optcal and Dschage Physcs

11 T(gas) DEPENDENCE OF DISSOCIATIVE ATTACHMENT Many ate coeffcents fo dssocatve attachment have a stong dependence on gas tempeatue due to vbatonal-otatonal exctaton of molecule. Potental Enegy U(R) ε > 0 Bound State Vbatonal Exctaton ε = 0 Dssocatve Cuve Potental Enegy U(R) Bound State ε ε 1 Vbatonal Exctaton ε < ε 1 Dssocatve Cuve o Intanuclea Sepaaton (R) o Intanuclea Sepaaton (R) NEGPLASMA_0903_10 Intenal enegy nceases ε: dk/dt gas < 0 Intenal enegy deceases ε: dk/dt gas > 0 Unvesty of Illnos Optcal and Dschage Physcs

12 T(gas) DEPENDENCE OF DISSOCIATIVE ATTACHMENT NEGPLASMA_0903_11 e N O N O- (P. Chanty, J. Chem. Phys. 51, 3369 (1969)) e C 4 F 10 C 4 F 10 - (L. Chstophoou, Cont. Plasma Phys. 7, 37 (1987)) Unvesty of Illnos Optcal and Dschage Physcs

13 ION PAIR FORMATION Although not usually a lage souce of negatve ons, on-pa fomaton typcally occus at hghe electon eneges. Example: e CF 4 CF 3 F- e CF 3 F - Coss Secton (A ) CF 3 F - R. A. Bonham, Jpn. J. Appl. Phys. 33, 4157 (1994) Electon Enegy (ev) NEGPLASMA_0903_1 Unvesty of Illnos Optcal and Dschage Physcs

14 LOSS PROCESSES: ION-ION NEUTRALIZATION Negatve ons ae consumed n the volume of plasmas pmaly by on-on neutalzaton A- B A B (o A* B o A B*) Requement: (Ionzaton Potental) B > (Electon Affnty) A Snce the Coulomb foces between ae long ange; atomc stuctue of the coe s not tebly mpotant. Rate coeffcents geneally depend on IP, EA, educed mass and scale as T Typcal values 10-7 cm 3 s -1 (300K) J. T. Moseley, Case Studes n Atomc Physcs 5, p. 1 (1975) NEGPLASMA_0903_13 Unvesty of Illnos Optcal and Dschage Physcs

15 LOSS PROCESSES: ASSOCIATIVE DETACHMENT Assocaton of small adcals to fom paent molecules can be acceleated by detachment as the lbeated electon caes off excess momentum O- O O e, k = x cm 3 s -1 O O U(R) O Do EA O O - Requement: Bond Enegy (D o ) > Electon Affnty O - R NEGPLASMA_0903_14 Unvesty of Illnos Optcal and Dschage Physcs

16 LOSS PROCESSES: CHARGE EXCHANGE Potental Enegy U(R) Just as postve ons undego chage exchange f enegetcally allowed (A B A B, IP(A) > IP(B)), negatve ons undego chage exchange. A- B A B- CF3 CF3 - o EA(CF) EA(F) CF F CF - F CF F - Intanuclea Sepaaton (R) Requement: EA (B) > EA(A) Example: CF - F CF F- Pocess could be stablzed. F CF ( CF ) 3 τ F ( CF ) CF ( ) * k CF M CF M 3 * k1 3 * 3 NEGPLASMA_0903_15 Unvesty of Illnos Optcal and Dschage Physcs

17 SECRET FOR MODELING ELECTRONEGATIVE PLASMAS: DO NOTHING SPECIAL Most appoxmaton methods fo electonegatve plasmas beakdown somewhee along the way and eque fxes. Includng all the physcs eally helps.fo example: dn dt do dt e = = n e 1 onzaton n e 1 onzaton do = neok dt attachment φ = q µ NE D q E = ε o O O k k e ecombnaton e ecombnaton - on-on neutalzaton n n O N O O O ( O O n ) e k k k n O k e attachment O O k - on-on neutalzaton φ O tanspot φ e tanspot φ O tanspot NEGPLASMA_0903_16 Unvesty of Illnos Optcal and Dschage Physcs

18 TRANSPORT OF NEGATIVE IONS In pncple, negatve ons ae smply heavy, cold electons (T I << T e ) and obey the same knetc and tanspot laws. In pactce, N- cannot clmb the plasma potental bae ceated by ambpola felds and so ae tapped n the plasma. Fo conventonal plasmas, N- ae almost exclusvely lost by volumetc pocesses. NEGPLASMA_0903_17 Unvesty of Illnos Optcal and Dschage Physcs

19 AMBIPOLOAR TRANSPORT WITH NEGATIVE IONS Unvesty of Illnos Optcal and Dschage Physcs NEGPLASMA_0903_18 In ambpola tanspot, typcally used wth global models, the total flux of chaged patcles leavng the plasma s zeo. = = = = = e e e e e A A dft ambpola fee dffuson A dft ambpola fee dffuson A e e dft ambpola e e fee dffuson e N n N N D n D N D E E N N D E N N D E n - n D µ µ µ Λ Λ Λ φ φ φ µ Λ φ µ Λ φ µ Λ φ Snce D e >> D I, the ambpola electc feld typcally acceleates postve ons, slows electons (and negatve ons)

20 AMBIPOLAR TRANSPORT WITH NEGATIVE IONS Poblem: Snce.. D >> D, T >> T, >> e I e I µ e µ I, then E A >> kti qλ whch usually esults n the unphyscal esult. φ - D = N - µ N E A Λ < 0 Many wok-aounds (all appoxmatons). One example s: E A = f ( N,N,n,D,D,D ) e neglect φ e < 0 φ > 0 good soluton NEGPLASMA_0903_19 Unvesty of Illnos Optcal and Dschage Physcs

21 ELECTRONEGATIVE CORE Low pessue plasmas have coes whch can be domnated by negatve ons; suounded by bounday egons and sheaths whee negatve ons ae excluded. PIC smulaton of plane paallel O plasma (10 mto) Ref: I. Kouznetsov, Plasma Souces Sc. Technol. 5, 66 (1996) NEGPLASMA_0903_0 Unvesty of Illnos Optcal and Dschage Physcs

22 HYBRID PLASMA EQUIPMENT MODEL MAGNETO- STATICS MODULE MATCH BOX-COIL CIRCUIT MODEL ELECTRO- MAGNETICS FREQUENCY DOMAIN ELECTRO- MAGNETICS FDTD σ(,z) J(,z,φ) ID(cols) B(,z) E(,θ,z,φ) B(,θ,z,φ) ELECTRON MONTE CARLO SIMULATION ELECTRON BEAM MODULE ELECTRON ENERGY EQUATION BOLTZMANN MODULE NON- COLLISIONAL HEATING ON-THE-FLY FREQUENCY DOMAIN Es(,z,φ) N(,z) S(,z,φ) Te(,z,φ) µ(,z,φ) CONTINUITY MOMENTUM ENERGY LONG MEAN FREE PATH (MONTE CARLO) SPUTTER MODULE POISSON ELECTRO- STATICS AMBIPOLAR ELECTRO- STATICS SIMPLE CIRCUIT MODULE SHEATH MODULE S(,z,φ) Es(,z,φ) Φ(,z,φ) s(,z) Φ(,z,φ) V(f),V(dc) MONTE CARLO FEATURE PROFILE MODEL IAD(,z) IED(,z) PLASMA CHEMISTRY MONTE CARLO SIMULATION MESO-SCALE MODULE SURFACE CHEMISTRY MODULE EXTERNAL CIRCUIT MODULE VPEM: SENSORS, CONTROLLERS, ACTUATORS SNLA_010_39 Unvesty of Illnos Optcal and Dschage Physcs

23 Unvesty of Illnos Optcal and Dschage Physcs ELECTROMAGNETICS MODULE AVS01_03 The wave equaton s solved n the fequency doman usng spase matx technques: Conductvtes ae tenso quanttes: ( ) ( ) t J E t E E E = σ ε µ µ 1 1 ))) ( ( )exp( ( ), ( t E t E ω ϕ = ( ) m m z z z z z z z m m n q m q E B B B B B B B B B B B B B B B B B B B B B B q m ν σ ν ω α σ α α α α α α α α α α α ν σ σ θ θ θ θ θ θ θ, / 1 = = = = Σ v

24 Contnuum: 3 ELECTRON ENERGY TRANSPORT 5 n ekte / t = S ( Te ) L( Te ) ΦkTe κ ( Te ) Te SEB whee S(T e ) = Powe deposton fom electc felds L(T e ) = Electon powe loss due to collsons Φ = Electon flux κ(t e ) = Electon themal conductvty tenso S EB = Powe souce souce fom beam electons Powe deposton has contbutons fom wave and electostatc heatng. ( t) f ε,, Knetc: A Monte Calo Smulaton s used to deve ncludng electon-electon collsons usng electomagnetc felds fom the EMM and electostatc felds fom the FKM. SNLA_010_41 Unvesty of Illnos Optcal and Dschage Physcs

25 Unvesty of Illnos Optcal and Dschage Physcs PLASMA CHEMISTRY, TRANSPORT AND ELECTROSTATICS Contnuty, momentum and enegy equatons ae solved fo each speces (wth ump condtons at boundaes). AVS01_ 05 Implct soluton of Posson s equaton: ( ) ( ) = Φ q t - - s N q t t φ ρ ε S N t N = ) v ( ( ) ( ) ( ) ( ) B v E m N q N v v kn T m t N v µ = 1 ( ) m m v v N N m ν ( ) ) ( ) U ( U Q E m N q N P t N ω ν ν ε ε = ± B B s T k R N N T T k R N N m m m E m N q 3 ) ( 3 ν

26 DEMONSTRATION OF CONCEPTS: SOLENOID ICP Demonstate concepts wth low pessue solenodal nductvely coupled plasma. Naow tube poduces hgh T e and lage negatve-on tappng plasma potentals. 1-d adal cuts ae taken though maxmum n negatve on densty He/O = 90/10, mto, sccm, 50 W Speces: He, He*, He O, O ( 1 ), O ( 1 Σ), O,O -, O, O( 1 D), O( 1 S), O, O - NEGPLASMA_0903_1 Unvesty of Illnos Optcal and Dschage Physcs

27 SOLENOID ICP: He/O = 90/10, 50 mto, 50 W Hgh specfc powe deposton n a naow tube and hgh plasma densty poduces a lage and unfom T e. The esultng plasma potental > 30 V. NEGPLASMA_0903_ Unvesty of Illnos Optcal and Dschage Physcs

28 SOLENOID ICP: He/O = 90/10, 50 mto, 50 W [e] extends to boundaes, [O-] s estcted to the coe of the plasma. T(O-) does not exceed an ev and so s not able to clmb the plasma potental. The dstbuton of postve ons (domnated by O ) s less unfom than electons as M shelds O - n the cente of the plasma. NEGPLASMA_0903_3 Unvesty of Illnos Optcal and Dschage Physcs

29 SOLENOID ICP: He/O = 90/10, 50 mto RADIAL PROPERTIES 3 egons defne the plasma. Electonegatve coe Electopostve halo Sheath NEGPLASMA_0903_4 Unvesty of Illnos Optcal and Dschage Physcs

30 SOLENOID ICP: He/O = 90/10, 50 mto vs T(O - ) T(O-) = T(gas) T(O-) = 0 x T(gas) Atfcally constanng T(O-) estcts (o expands) the egon of plasma accessble to negatve ons. NEGPLASMA_0903_5 Unvesty of Illnos Optcal and Dschage Physcs

31 SOLENOID ICP: He/O = 90/10, 50 W vs PRESSURE In spte of nceasng plasma potental, voltage dop n the cente of the plasma s not that dffeent, and so extent of O- s about the same T(O-) also nceases wth deceasng pessue. NEGPLASMA_0903_6 Unvesty of Illnos Optcal and Dschage Physcs

32 ICP: COMPLEX GEOMETRY AND CHEMISTRY Inductvely coupled plasmas fo mcoelectoncs fabcaton often use complex electonegatve gas mxtues. Etch selectvty s obtaned fom egulatng thckness of polyme layes. Example case: 10 mto, 1000 W, 100 sccm A/C 4 F 8 /CO/O =73/7.3/18/1.8 NEGPLASMA_0903_7 Unvesty of Illnos Optcal and Dschage Physcs

33 A/C 4 F 8 /CO/O ICP: ELECTRIC FIELD, POWER, POTENTIAL Plasma peaks on axs wth pull towads peak n powe deposton whee postve ons ae domnantly fomed. NEGPLASMA_0903_8 10 mto, 1000 W, 100 sccm A/C 4 F 8 /CO/O =73/7.3/18/1.8 Unvesty of Illnos Optcal and Dschage Physcs

34 A/C 4 F 8 /CO/O ICP: [e], [N ], [N - ] [e] nea maxmum n plasma potental. Negatve ons sheld postve ons at the low and hgh values. Catephoess dsplaces negatve ons towads boundaes. NEGPLASMA_0903_9 10 mto, 1000 W, 100 sccm A/C 4 F 8 /CO/O =73/7.3/18/1.8 Unvesty of Illnos Optcal and Dschage Physcs

35 A/C 4 F 8 /CO/O ICP: [A ], [F - ] Negatve ons, tapped n the plasma, flow towads peak of plasma potental whee they undego on-on neutalzaton. Postve ons lagely flow to boundaes. NEGPLASMA_0903_30 10 mto, 1000 W, 100 sccm A/C 4 F 8 /CO/O =73/7.3/18/1.8 Unvesty of Illnos Optcal and Dschage Physcs

36 A/C 4 F 8 /CO/O ICP: [C 4 F 8- ] C 4 F 8 -, beng heave and less moble, s moe susceptble to beng tapped n small local extema of the plasma potental. These tappng zones ae often the pecuso to dust patcle fomaton. 10 mto, 1000 W, 100 sccm A/C 4 F 8 /CO/O =73/7.3/18/1.8 NEGPLASMA_0903_31 Unvesty of Illnos Optcal and Dschage Physcs

37 MOMENTUM TRANSFER: CATAPHORESIS Due to the lage Coulomb scatteng coss secton, thee s effcent momentum tansfe between postve and negatve ons. Lage flux of postve ons movng towads boundaes pushes negatve ons n the same decton. dφ dt ( v ) =... Φ N σm v Ths s a patculaly mpotant pocess when negatve ons ae chaged dust patcles ( on-dag ) NEGPLASMA_0903_3 Unvesty of Illnos Optcal and Dschage Physcs

38 CATAPHORESIS IN ICPs When the flux of postve ons s lage and electonegatvty (N - /N ) small, momentum tansfe fom N to N - can be mpotant. A/Cl =50/50, 100 sccm, 500 W, 10 mto NEGPLASMA_0903_33 Unvesty of Illnos Optcal and Dschage Physcs

39 CATAPHORESIS IN ICPs The Coulomb momentum tansfe coss secton between N - and N scales nvesely wth enegy. σ = Ψ 3 kψ = 6 ( K ) 3 ln Λ cm kt I, 1 η v v Ion dag s theefoe senstve to tempeatue and speed of nteacton; deceasng n mpotance as both ncease. A/Cl =50/50, 100 sccm, 500 W, 10 mto NEGPLASMA_0903_34 Unvesty of Illnos Optcal and Dschage Physcs

40 CHARGING DAMAGE IN MICROELECTRONICS FABRICATION In mcoelectoncs fabcaton, tenches ae etched nto slcon substates Ions ave wth vetcal taectoes. Electons ave wth boad themal taectoes. The top of the tench s chaged negatve; the bottom postve. Ion taectoes ae petubed by electc felds n the tench. Plasma nduced damage such as notchng, bowng, mcotenchng can then occu. Chage n the bottom of the tench can be neutalzed acceleatng negatve ons nto the wafe NEGPLASMA_0903_ Bowng Mco Tenchng Postve Ions Notchng Induced Cuents Unvesty of Illnos Optcal and Dschage Physcs

41 PULSED PLASMAS FOR NEGATIVE ION EXTRACTION Dung cw opeaton of ICPs, negatve ons cannot escape the plasma. By pulsng the plasma (tun powe on-off), dung the off peod (the afteglow ) The electon tempeatue deceases Plasma potental deceases Negatve on fomaton (usually) nceases Negatve ons can escape NEGPLASMA_0903_36 Unvesty of Illnos Optcal and Dschage Physcs

42 The deal gas mxtue s low attachng at hgh T e (powe-on) and hghly attachng at low T e (powe-off) A/Cl mxtues have these popetes. Dssocatve attachment coss secton peaks at themal eneges. e Cl Cl Cl- Rapd attachment occus n the afteglow. Electon mpact coss sectons fo Cl. Ref: J. Olthoff, Appl. J. Phys. Chem. Ref. Data, 8, 130 (1999) Unvesty of Illnos NEGPLASMA_0903_37 PULSED PLASMAS: A/Cl GAS CHEMISTRIES Optcal and Dschage Physcs

43 GLOBAL MODELING: PULSED A/Cl ICPs Spkng of T e occus at leadng edge of powe pulse as electon densty s low poducng apd onzaton. Rapd themalzaton n afteglow tuns off onzaton; nceases attachment. A/Cl = 70/30, 15 mto, khz, 0% duty cycle. NEGPLASMA_0903_38 Unvesty of Illnos Optcal and Dschage Physcs

44 GLOBAL MODELING: PULSED A/Cl ICPs Rapd attachment n the afteglow poduces an on-on plasma; chage balance s met by negatve ons, not electons. Ambpola felds dsspate and negatve ons can escape. A/Cl = 70/30, 15 mto, khz, 0% duty cycle. NEGPLASMA_0903_39 Unvesty of Illnos Optcal and Dschage Physcs

45 REACTOR AND CONDITIONS 5 cm Gas Feed Uppe Electode Assembly 5-tun spal col Quatz Wndow 11.6 cm 4.05 cm 16.5 cm Electode Extenson Smulatons wee pefomed n a GECRC Standad Lowe Electode Insulato Peak nput powe : 300 W Pulse epetton fequency : 10 khz Pessue : 0 mto NEGPLASMA_0903_40 Pump Pot Inlet gas flow ate : 0 sccm A, A/Cl = 80/0 Unvesty of Illnos Optcal and Dschage Physcs

46 -D DYNAMICS IN A/Cl : PLASMA POTENTIAL AND Cl - FLUX VECTORS As the pulse begns, the peak plasma potental mgates to unde the cols. A/Cl = 80/0, 0 mto, 300 W, 10 khz/50% As the steady state s eached, the peak plasma potental moves towads the cente. Cl - flux vectos pont towads the peak plasma potental when plasma potental s lage. It takes about 5 µs fo the ons to move fom pephey to the cente. When the plasma s tuned off, Cl - flux vectos evese, pontng towads boundaes. NEGPLASMA_0903_4 Anmaton Slde -3 V 35 V Unvesty of Illnos Optcal and Dschage Physcs

47 -D DYNAMICS IN A/Cl : Cl - DENSITY Dung powe on, the plasma potental peaks theeby "compessng" the [Cl - ] A/Cl = 80/0, 0 mto, 300 W, 10 khz/50% At steady state, [Cl - ] "ebounds" as the plasma potental deceases Due to neta, [Cl - ] does not espond to changes n plasma potental mmedately. When the plasma s tuned off, the [Cl - ] nceases due to a hghe ate of dssocatve attachment at low T e. Late, the plasma potental falls and [Cl - ] speads NEGPLASMA_0903_41 1 x 10 9 cm -3 Anmaton Slde 3 x cm -3 Unvesty of Illnos Optcal and Dschage Physcs

48 [e] vs PULSE REPETITION FREQUENCY (PRF) Electon Densty (10 11 cm -3 ) Powe On 10 khz 0 khz 5 khz 5 khz Non-monotonc behavo n peak [e]. Lowe PRF esults n hghe ate of dssocaton due to hghe T e poducng less dssocatve attachment Tme (µs) NEGPLASMA_0903_43 A/Cl = 80/0, 0 mto, 300 W, 10 khz, 50% duty cycle Unvesty of Illnos Optcal and Dschage Physcs

49 [Cl-] vs PULSE REPETITION FREQUENCY (PRF) Cl - Densty (10 11 cm -3 ) Powe On 10 khz 0 khz khz 5 khz Tme (µs) [Cl - ] nceases at plasma tun on as the Cl - ons move to the cente of plasma; and then decease as ecombnaton occus. When powe s emoved, [Cl - ] nceases wth dop n T e, and then deceases as Cl- dffuses to walls. NEGPLASMA_0903_44 A/Cl = 80/0, 0 mto, 300 W, 10 khz, 50% duty cycle Unvesty of Illnos Optcal and Dschage Physcs

50 Postve on and electon flux (10 15 cm - s -1 ) FLUXES TO SUBSTRATE: DUTY CYCLE Electon and Postve on flux Cl - Cl - e e Tme (µs) Cl - flux(10 14 cm - s -1 ) Postve on and electon flux (10 15 cm - s -1 ) Duty cycle : 10% A fnte tme s equed to tanston to on-on plasma n the afteglow wth a low plasma potental. Fo a gve epetton ate, smalle duty cycles (longe afteglow) poduces longe pulses of Cl- fluxes to the substate. NEGPLASMA_0903_45 A/Cl = 80/0, 0 mto, 300 W, 10 khz Electon and Postve on flux Cl - Cl - 10 e e Tme (µs) Duty cycle : 50% 10 Cl - flux(10 14 cm - s -1 ) Unvesty of Illnos Optcal and Dschage Physcs 8 6 4

51 ELECTRONEGATIVE PLASMAS: ATMOSPHERIC PRESSURE The vast maoty of atmosphec pessue plasmas havng sgnfcant electonegatvty ae pulsed, tansent o flamentay. What changes at atmosphec pessue? Avalablty of 3 d body nceases ates of assocaton eactons; and s the bass of excme fomaton. Xe Cl M XeCl ( B) M Xe Cl hν Knetcs ae local n that tanspot fo negatve s not tebly mpotant. Due to hghe gas denstes, ates of attachment ae hghe, makng tanstons to on-on plasmas moe apd. Statonay negatve ons povde local sheldng of postve ons, patculaly n afteglow stuatons. NEGPLASMA_0903_46 Unvesty of Illnos Optcal and Dschage Physcs

52 PLASMA SURFACE MODIFICATION OF POLYMERS Unteated PP To mpove wettng and adheson of polymes atmosphec plasmas ae used to geneate gas-phase adcals to functonalze the sufaces. Polypopylene (PP) Plasma Teated PP He/O /N Plasma M. Stobel, 3M UTA_110_08 Massnes et al. J. Phys. D 31, 3411 (1998). Unvesty of Illnos Optcal and Dschage Physcs

53 FUNCTIONALIZATION OF POLYPROPYLENE Unteated PP s hydophobc. Inceases n suface enegy by plasma teatment ae attbuted to the functonalzaton of the suface wth hydophlc goups. Cabonyl (-C=O) Alcohols (C-OH) Peoxy (-C-O-O) Acds ((OH)C=O) The degee of functonalzaton depends on pocess paametes such as gas mx, enegy deposton and elatve humdty (RH). At suffcently hgh enegy deposton, eoson of the polyme occus. UTA_110_13 Unvesty of Illnos Optcal and Dschage Physcs

54 REACTION PATHWAY e e e e N HUMID-AIR PLASMA e e O N N H HO OH O O O O 3 NO O BOUNDARY LAYER O NO OH, HO OH OH, O OH H O O C C C C C C C C C O LAYER 1 POLYPROPYLENE H C C C C C C C C C C LAYER OH C C C C C C C C C C C LAYER 3 RAJESH_AVS_0_05 Unvesty of Illnos Optcal and Dschage Physcs

55 POLYMER TREATMENT APPARATUS TYPICAL PROCESS CONDITIONS: Web speed : m/mn Resdence tme : a few s Enegy deposton : J cm - Appled voltage : 10-0 kv at a few 10s khz Gas gap : a few mm GROUNDED ELECTRODE FEED ROLL PLASMA POWERED SHOE ELECTRODE COLLECTOR ROLL ~ HIGH-VOLTAGE POWER SUPPLY RAJESH_AVS_0_04A Unvesty of Illnos Optcal and Dschage Physcs

56 COMMERCIAL CORONA PLASMA EQUIPMENT Tantec Inc. RAJESH_AVS_0_04 Unvesty of Illnos Optcal and Dschage Physcs

57 HIGH PRESSURE PLASMA SIMULATION: non-pdpsim -d ectlnea o cylndcal unstuctued mesh Implct dft-dffuson fo chaged and neutal speces Posson s equaton wth volume and suface chage, and mateal conducton. Ccut model Electon enegy equaton coupled wth Boltzmann soluton fo electon tanspot coeffcents Optcally thck adaton tanspot wth photoonzaton Seconday electon emsson by mpact Themally enhanced electc feld emsson of electons Suface chemsty. Monte Calo Smulaton fo seconday electons Compessble Nave Stokes fo hydodynamc flow Maxwell Equatons n fequency doman NEGPLASMA_0903_47 Unvesty of Illnos Optcal and Dschage Physcs

58 DESCRIPTION OF MODEL: CHARGED PARTICLES, POTENTIAL Contnuty wth souces due to electon mpact, heavy patcle eactons, suface chemsty, photo-onzaton and seconday emsson. N t v = φ Chaged patcle fluxes by modfed Shafette-Gummel expesson fo dft-dffuson. Assumng collsonal couplng between ons and flow feld, v f, advectve feld s ncluded: S αd( n n exp( α x )) 1 1 ϕ 1 =, α = qµ ( ( 1 exp( α x ) x Φ Φ ) v f Posson s Equaton fo Electc Potental: ε Φ = ρ V ρ S ECOIL_0803_ Unvesty of Illnos Optcal and Dschage Physcs

59 DESCRIPTION OF MODEL: CHARGED PARTICLE SOURCES Photoonzaton: v v N ( ) σ N ( )exp v S = P ( ) v v 4π Electc feld and seconday emsson: S S =, Volumetc Plasma Chage: ρv = t ( q ) φ Suface and n Mateal Chages: ρ ( ( )) S = qφ 1 γ σ ( Φ ) t E = AT exp ( ) 1/ Φ W 3 ( q E/ ε ) kt S v v λ 0 d, v ( ) 3 S = γ φ E ECOIL_0803_3 Unvesty of Illnos Optcal and Dschage Physcs

60 DESCRIPTION OF MODEL: ELECTRON ENERGY, TRANSPORT COEFFICIENTS Electon enegy equaton mplctly ntegated usng Successve- Ove-Relaxaton: ( n ε ) e t = E n e 5 Nκ εϕ λ T e, = qφ e Electon tanspot coeffcents obtaned fom -tem sphecal hamonc expanson of Boltzmann s Equaton. Ion tanspot coeffcents obtaned fom tabulated values fom the lteatue o usng conventonal appoxmaton technques. ECOIL_0803_5 Unvesty of Illnos Optcal and Dschage Physcs

61 DESCRIPTION OF MODEL: SECONDARY ELECTRONS-MONTE CARLO SIMULATION Tanspot of enegetc seconday electons s addessed wth a Monte Calo Smulaton. MCS s peodcally executed to povde electon mpact souce functons fo contnuty equatons fo chaged and neutal patcles. Algothms n MCS account fo lage dynamc ange n mesh esoluton, electc feld, and eactant denstes. ECOIL_0803_7 Unvesty of Illnos Optcal and Dschage Physcs

62 DESCRIPTION OF MODEL: MCS MESHING Select egons n whch hgh enegy electon tanspot s expected. Supempose Catesan MCS mesh on unstuctued flud mesh. Constuct Geens functons fo ntepolaton between meshes. ECOIL_0803_8 Unvesty of Illnos Optcal and Dschage Physcs

63 ELECTROMAGNETICS MODEL The wave equaton s solved n the fequency doman. 1 E µ = t ( εe ) ( σe J ) t antenna All quanttes ae complex fo to account fo fnte collson fequences. Solved usng method of Successve-ove-Relaxaton ECOIL_0803_30 Unvesty of Illnos Optcal and Dschage Physcs

64 COMPRESSIBLE NAVIER STOKES Flud aveaged values of mass densty, mass momentum and themal enegy densty obtaned n usng unsteady algothms. ( ρc T ) t ρ = ( ρv ) ( nlets, pumps ) t ( ρv) = NkT ρvv µ t p = ( ) ( ) ( κ T ρvc T ) P v R H p f q N v E E ECOIL_0803_31 Unvesty of Illnos Optcal and Dschage Physcs

65 DESCRIPTION OF MODEL: NEUTRAL PARTICLE UPDATE Tanspot equatons ae mplctly solved usng Successve-Ove- Relaxaton: ( t t) = N ( t) N ( t t) N v f D NT SV N T Suface chemsty s addessed usng flux-n/flux-out bounday condtons wth eactve stckng coeffcents SS = ( ) φ γ S S ECOIL_0803_6 Unvesty of Illnos Optcal and Dschage Physcs

66 ATMOSPHERIC PRESSURE LINEAR CORONA Demonstate concepts of pulsed atmosphec pessue electonegatve plasma wth lnea coona dschage as used n polyme functonalzaton. Devce s functonally a delectc bae dschage. Dschage s ntated by feld emsson fom cathode. Dy A N /O = 80/0, -15 kv, mm gap NEGPLASMA_0903_48 Unvesty of Illnos Optcal and Dschage Physcs

67 LINEAR CORONA: NEGATIVE ION DYNAMICS Dssocatve attachment (e O O - O) has a 5 ev theshold enegy. Occus domnantly n hgh E/N egons. 3-body non-dssocatve attachment (e O M O - M) has no theshold. Occus wth fequency 4 x 10 8 s -1 ( ns lfetme) n atmosphec pessue a. O - chage exchanges wth O (O - O O - O -, k = 1.5 x cm 3 s -1 ). Wth maxmum O densty (4 x cm -3 ), lfetme s 0.1 µs (not vey mpotant). O - assocates by deattachment wth O (O - O O e, k = x cm 3 s -1 ). Wth maxmum O densty (4 x cm -3 ), lfetme s 0.1 µs (not vey mpotant). Negatve ons ae faly stable (and mmoble) untl on-on neutalzaton [k(effectve- body)= 5 x 10-6 cm 3 s -1, lfetme 10 s ns]. NEGPLASMA_0903_54 Unvesty of Illnos Optcal and Dschage Physcs

68 LINEAR CORONA: [e], E/N Electon densty bdges gap sustaned by onzaton poduced by chage enhanced E/N. Electons spead on delectc web as chage accumulates. N /O = 80/0, -15 kv, 100 ns (log-tme) NEGPLASMA_0903_49 Unvesty of Illnos Optcal and Dschage Physcs

69 LINEAR CORONA: [e], E/N Electon densty bdges gap sustaned by onzaton poduced by chage enhanced E/N. Electons spead on delectc web as chage accumulates. N /O = 80/0, -15 kv, 100 ns (log-tme) Anmaton Slde NEGPLASMA_0903_50 Unvesty of Illnos Optcal and Dschage Physcs

70 LINEAR CORONA: POTENTIAL, CHARGE Chage densty sustans E/N at font of avalanche. Electc potental s shelded fom the gap by chagng of the delectc web. N /O = 80/0, -15 kv, 100 ns (log-tme) NEGPLASMA_0903_51 Unvesty of Illnos Optcal and Dschage Physcs

71 LINEAR CORONA: POTENTIAL, CHARGE Chage densty sustans E/N at font of avalanche. Electc potental s shelded fom the gap by chagng of the delectc web. N /O = 80/0, -15 kv, 100 ns (log-tme) Anmaton Slde NEGPLASMA_0903_5 Unvesty of Illnos Optcal and Dschage Physcs

72 LINEAR CORONA: TOTAL POSITIVE ION DENSITY Postve ons: N, N 4, N, O, O. Heavy ons at atmosphec pessue ae nealy mmoble dung shot duaton of pulse. Loss s domnantly by local pocesses (e-on ecombnaton, on-on neutalzaton). N /O = 80/0, -15 kv, 100 ns (log-tme) Anmaton Slde NEGPLASMA_0903_53 Unvesty of Illnos Optcal and Dschage Physcs

73 LINEAR CORONA: NEGATIVE IONS O -, O - Rapd conveson of e to O - by 3-body pocesses poduces an on-on plasma n afteglow. Nealy mmoble negatve ons (µ= cm /V-s, v dft = 10 5 cm/s) ae lagely consumed whee fomed by on-on neutalzaton. N /O = 80/0, -15 kv, 100 ns (log-tme) NEGPLASMA_0903_55 Unvesty of Illnos Optcal and Dschage Physcs

74 LINEAR CORONA: NEGATIVE IONS O -, O - Rapd conveson of e to O - by 3-body pocesses poduces an on-on plasma n afteglow. Nealy mmoble negatve ons (µ= cm /V-s, v dft = 10 5 cm/s) ae lagely consumed whee fomed by on-on neutalzaton. N /O = 80/0, -15 kv, 100 ns (log-tme) Anmaton Slde NEGPLASMA_0903_56 Unvesty of Illnos Optcal and Dschage Physcs

75 CONCLUDING REMARKS As you develop you models fo electonegatve plasmas (o any type plasma) Constuct you models as GENERALLY as possble. Neve, neve, neve hadwe any speces o chemcal eacton mechansm n you code. Read all optons, speces, mechansms as nput fom WELL MAINTAINED AND DOCUMENTED DATABASES. Develop STANDARDS fo nput, output, use of databases and vsualzaton whch ALL of you codes obey. DOCUMENT, DOCUMENT, DOCUMENT!!! Evey nput-vaable, evey output-paamete, evey pocess. Have offcal vesons. ARCHIVE, ARCHIVE, ARCHIVE!!! Example cases, documentaton, best pactce, offcal veson. A compute knowledgeable peson should be able to un cases n a day. NEGPLASMA_0903_57 Unvesty of Illnos Optcal and Dschage Physcs

76 ACKNOWLEDGEMENTS Postdoctoal Reseach Fellows: D. Alex Vasenkov D. Wenl Collson Gaduate Students (past and pesent) Pamod Subamonum Raesh Doa D. Shane Staffod Fundng Agences Natonal Scence Foundaton Semconducto Reseach Cop. 3M Inc. NEGPLASMA_0903_58 Unvesty of Illnos Optcal and Dschage Physcs