MODELING OF INTEGRATED PLASMA PROCESSING: PLASMA PHYSICS, PLASMA CHEMISTRY AND SURFACE KINETICS

Transcription

1 MODELING OF INTEGRATED PLASMA PROCESSING: PLASMA PHYSICS, PLASMA CHEMISTRY AND SURFACE KINETICS Mak J. Kushne Depatment of Electcal and Compute Engneeng Ubana, IL May 2003 CFDRC_0503_01

2 AGENDA Integaton n Plasma Pocessng Modelng Requements: Plasma Physcs Plasma Chemsty Suface Knetcs Integated pocess modelng of etchng and cleanng of poous slca; and metal deposton fo nteconnect wng. Concludng Remaks CFDRC_0503_02

3 COLLISIONAL LOW TEMPERATURE PLASMAS Patally onzed plasmas ae gases contanng neutal atoms and molecules, electons, postve ons and negatve ons. These systems ae the plasmas of evey day technology. WALL PLUG POWER CONDITIONING ENERGETIC ELECTRONS e E ELECTRIC FIELDS COLLISIONS WITH ATOMS/MOLECULES A EXCITATION, IONIZATION, DISSOCIAITON (CHEMISTRY) PHOTONS RADICALS IONS LAMPS LASERS ETCHING DEPOSITION Electons tansfe powe fom the "wall plug" to ntenal modes of atoms / molecules to "make a poduct, vey much lke combuston. The electons ae hot (seveal ev o 10-30,000 K) whle the gas and ons ae cool, ceatng non-equlbum plasmas. CFDRC_0503_03

4 COLLISIONAL LOW TEMPERATURE PLASMAS Thustes Lghtng Spay Coatngs Mateals Pocessng UTA_1102_05 Dsplays

5 PLASMAS IN MICROELECTRONICS FABRICATION The stkng mpovement n the functonalty of mcoelectoncs devces esults fom shnkng of ndvdual components and nceasng complexty of the ccuty UTA_1102_29 Ref: IBM Mcoelectoncs Plasmas ae absolutely essental to the fabcaton of mcoelectoncs.

6 PLASMAS IN MICROELECTRONICS FABRICATION Plasmas play a dual ole n mcoelectoncs fabcaton. Fst, electon mpact on othewse uneactve gases poduces neutal adcals and ons. These speces then dft o dffuse to sufaces whee they add, emove o modfy mateals. UTA_1102_30

7 PLASMAS IN MICROELECTRONICS FABRICATION Second, ons delve dected actvaton enegy to sufaces fabcatng fne havng exteme and epoducable toleances µm Featue (C. Cu, AMAT) UTA_1102_31

8 APPLIED MATERIALS DECOUPLED PLASMA SOURCES (DPS) PLSC_0901_06

9 f BIASED INDUCTIVELY COUPLED PLASMAS Inductvely Coupled Plasmas (ICPs) wth f basng ae used hee. < 10s mto, 10s MHz, 100s W kw, electon denstes of cm SOLENOID DOME HEIGHT (cm) 0 GAS INJECTORS BULK PLASMA f BIASED SUBSTRATE WAFER PUMP PORT RADIUS (cm) s COILS s POWER SUPPLY ADVMET_1002_10 POWER SUPPLY

10 PHYSICAL PROCESSES IN REACTOR 26 SOLENOID (magnetostatcs) DOME (suface chemsty, sputte physcs) HEIGHT (cm) 0 BULK PLASMA (plasma hydodynamcs, knetcs, chemsty, electostatcs, electomagnetcs) GAS INJECTORS (flud dynamcs) f BIASED SUBSTRATE WAFER COILS (electomagnetcs) PUMP PORT RADIUS (cm) POLYMER (suface chemsty, sputte physcs) M + e WAFER Seconday emsson (beam physcs) E-FIELD (sheath physcs) s PROFILE EVOLUTION (suface chemsty, sputte physcs, electostatcs) s POWER SUPPLY (ccuty) POWER SUPPLY (ccuty) CFDRC_0503_04

11 GOAL FOR PROCESS MODELING: INTEGRATION Plasma pocessng nvolves an ntegated sequence of steps, each of whch depends on the qualty of the pevous steps. CFDRC_0503_05

12 GOAL FOR PROCESS MODELING: INTEGRATION To addess these complextes, modelng platfoms must ntegate: Plasma Physcs Plasma Chemsty Suface Knetcs CFDRC_0503_06

13 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_0102_39

14 ELECTROMAGNETICS MODEL EIND_0502_10 The wave equaton s solved n the fequency doman usng spase matx technques (2D,3D): Conductvtes ae tenso quanttes (2D,3D): ( ) ( ) t J E t E E E + + = + σ ε µ µ ))) ( ( )exp( ( ), ( t E t E ω +ϕ = ( ) m e 2 o m 2 z 2 z z z 2 2 z z z m o m n q m q E j B B B B B B B B B B B B B B B B B B B B B B 1 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 = + = = =, / v

15 ELECTROMAGNETICS MODEL (cont.) The electostatc tem n the wave equaton s addessed usng a petubaton to the electon densty (2D). E = ρ ε = q n ε e, n e σ E = q / 1 + τ ω J e Conducton cuents can be knetcally deved fom the Electon Monte Calo Smulaton to account fo non-collsonal effects (2D). ( ( ) (, t) = J ( ) exp( ( ω t + φ ( ))) = qn ( ) v ( ) exp ωt + φ ( ) o v e e v EIND_0502_11

16 Contnuum (2D,3D): 3 2 ELECTRON ENERGY TRANSPORT 5 n ekte / t = S + 2 ( 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 (2D,3D): 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_0102_41

17 PLASMA CHEMISTRY, TRANSPORT AND ELECTROSTATICS Contnuty, momentum and enegy equatons ae solved fo each speces (wth jump condtons at boundaes) (2D,3D). AVS01_ 05 Implct soluton of Posson s equaton (2D,3D): ( ) ( ) + = + 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 ( ) j j j j m m j v v N N m j ν + ( ) ) ( ) U ( U Q E m N q N P t N ω ν ν ε ε + = ± j j B j j j j B j j j j s T k R N N T T k R N N m m m E m N q 3 ) ( ν

18 WALK THROUGH: A/Cl 2 PLASMA FOR p-s ETCHING The nductvely coupled electomagnetc felds have a skn depth of 3-4 cm. Absopton of the felds poduces powe deposton n the plasma. Electc Feld (max = 6.3 V/cm) A/Cl 2 = 80/20 20 mto 1000 W ICP 2 MHz 250 V bas, 2 MHz (260 W) EIND_0502_05

19 A/Cl 2 ICP: POWER AND ELECTRON TEMPERATURE ICP Powe heats electons, capactvely coupled powe domnantly acceleates ons. Powe Deposton (max = 0.9 W/cm 3 ) Electon Tempeatue (max = 5 ev) EIND_0502_06 A/Cl 2 = 80/20, 20 mto, 1000 W ICP 2 MHz, 250 V bas, 2 MHz (260 W)

20 A/Cl 2 ICP: IONIZATION Ionzaton s poduced by bulk electons and sheath acceleated seconday electons. EIND_0502_07 Beam Ionzaton (max = 1.3 x cm -3 s -1 ) A/Cl 2 = 80/20, 20 mto, 1000 W ICP 2 MHz, 250 V bas, 2 MHz (260 W) Bulk Ionzaton (max = 5.4 x cm -3 s -1 )

21 A/Cl 2 ICP: POSITIVE ION DENSITY Dffuson fom the emote plasma souce poduces unfom on denstes at the substate. Postve Ion Densty (max = 1.8 x cm -3 ) EIND_0502_08 A/Cl 2 = 80/20, 20 mto, 1000 W ICP 2 MHz, 250 V bas, 2 MHz (260 W)

22 PLASMA PHYSICS (Ae we gettng t ght?) CFDRC_0503_07

23 FORCES ON ELECTRONS IN ICPs vθ B R, B Z B R Eθ δ vθ x B R λs Es Inductve electc feld povdes azmuthal acceleaton; penetates 1 2 (1-3 cm) δ = ( m ( e µ n ) 2 e Electostatc (capactve); penetates (100s µm to mm) Non-lnea Loentz Foce o e F 2 λ S 10λ D, λd = kte ( 8πnee ) = v θ B f 1 ( ) 2 EIND_0502_09

24 ANAMOLOUS SKIN EFFECT AND POWER DEPOSITION Collsonal heatng: λ mfp < δ skn, J e (, t) = σ, Anomalous skn effect: (, t) E( t) Ref: V. Godyak, Electon Knetcs of Glow Dschages EIND_0502_12 J e λ mfp (, t) = σ F = > δ (, ', t, t' ) E( ', t' ) v skn B Electons eceve (postve) and delve (negatve) powe fom/to the E-feld. E-feld s non-monotonc. d ' dt'

25 ICP CELL FOR VALIDATION Expements by Godyak et al ae used fo valdaton. The expemental cell s an ICP eacto wth a Faaday sheld to mnmze capactve couplng. V. Godyak et al, J. Appl. Phys. 85, 703 (1999) EIND_0502_18

26 ELECTRON DENSITY: A, 10 mto, 200 W, 7 MHz 4 3 [e] cm EXP. R =0 cm (x 0.75) EXP. R =4 cm (x 0.75) HEIGHT (cm) Ref: V. Godyak, Pvate Comm. On axs peak n [e] occus nspte of off-axs powe deposton. Model s about 30% below expements. Ths lkely has to do wth detals of the sheath model. EIND_0502_19

27 ELECTRON TEMPERATURE: A, 10 mto, 200 W, 7 MHz 4 ELECTRON TEMPERATURE (ev) 3 2 EXP. R =0 cm EXP. R =4 cm HEIGHT (cm) Ref: V. Godyak, Pvate Comm. The hgh themal conductvty and edstbuton of enegy by e-e collsons poduces nealy unfom tempeatues. T e peaks unde the cols whee powe deposton s lagest. EIND_0502_20

28 EEDs ALONG THE CENTERLINE OF THE REACTOR Godyak (1998), z=5.0 cm Model, z=0.5 cm Model, z=5.0 cm Model, z=10.0 cm EED (ev -3/2 ) W, =0.0 cm The electon enegy dstbutons show a b- Maxwellan fom, whch s typcal fo low-pessue nductvely coupled plasmas Enegy (ev) CFDRC_0503_08 A, 10 mto, 6.78 MHz, 200 W

29 COLLISIONLESS TRANSPORT ELECTRIC FIELDS We couple electon tanspot to Maxwell s equatons by knetcally devng electon cuent. j( ) exp( ω( t to )) da = q v exp ω t t k k k ( ) ( ( )) E θ dung the f cycle exhbts extema and nodes esultng fom ths non-collsonal tanspot. k o Sheets of electons povde cuent souces ntefeng o enfocng E θ fo the next sheet. Axal tanspot esults fom foces. v B f ANIMATION SLIDE CFDRC_0503_09 A, 10 mto, 7 MHz, 100 W

30 POSITIVE POWER DEPOSITION: POSITIVE AND NEGATIVE The end esult s egons of postve and negatve powe deposton. NEGATIVE SNLA_0102_19 A, 10 mto, 7 MHz, 100 W

31 POWER DEPOSITION vs FREQUENCY The shote skn depth at hgh fequency poduces moe layes of negatve powe deposton of lage magntude. Ref: Godyak, PRL (1997) 6.7 MHz (5x W/cm 3 ) A, 10 mto, 200 W 13.4 MHz (8x W/cm 3 ) SNLA_0102_32 MIN MAX

32 TIME DEPENDENCE OF THE EED Tme vaaton of the EED s mostly at hghe eneges whee electons ae moe collsonal. Dynamcs ae domnantly n the electomagnetc skn depth whee both collsonal and nonlnea Loentz Foces) peak. The second hamonc domnates these dynamcs. SNLA_0102_10 A, 10 mto, 100 W, 7 MHz, = 4 cm ANIMATION SLIDE

33 TIME DEPENDENCE OF THE EED: 2 nd HARMONIC Electons n skn depth quckly ncease n enegy and ae launched nto the bulk plasma. Undegong collsons whle tavesng the eacto, they degade n enegy. Those suvvng clmb the opposte sheath, exchangng knetc fo potental enegy. Seveal pulses ae n tanst smultaneously. SNLA_0102_11 A, 10 mto, 100 W, 7 MHz, = 4 cm Ampltude of 2 nd Hamonc ANIMATION SLIDE

34 CONSEQUENCES OF ELECTRON DYNAMICS IN ICPs The consequences of electon dynamcs wee nvestgated fo A/N 2 gas mxtues. e - + A A + + e - + e -, ε = 16 ev Hgh theshold eactons captue modulaton n the tal of the EED. e - + N 2 N 2 (vb) + e -, ε = 0.29 ev Low theshold eactons captue modulaton of the bulk of the EED. Base case condtons: Pessue: 5 mto Fequency: MHz A / N 2 : 90 / 10 Powe : 650 W CFDRC_0503_ Electon densty (10 11 cm -3 )

35 SOURCES FUNCTION vs TIME: THRESHOLD Ionzaton of A has moe modulaton than vbatonal exctaton of N 2 due to modulaton of the tal of the EED. Ionzaton of A 6 x x cm -3 s -1 Exctaton of N 2 (v) 1.4 x x cm -3 s -1 ANIMATION SLIDE SNLA_0102_26 MIN MAX

36 HARMONICS OF A IONIZATION: FREQUENCY At lage ω, non-lnea Loentz foces ae small, and so hamonc content s also small. At small ω, both non-lnea Loentz foces and hamonc exctaton by the electc feld ae lage. CFDRC_0503_27 A/N 2 =90/10, 5 mto Sn / S S4 S1, S3 S Fequency (MHz) Hamonc Ampltude/Tme Aveage

37 PLASMA CHEMISTRY (Ae we gettng ths ght?)

38 REACTION MECHANISMS FOR PLASMA ETCHING Recpes fo plasma etchng of delectc mateals (e.g., SO 2, S 3 N 4 ) often contan mxtues of many gases such as: A, C 4 F 8, O 2, N 2, CO The fluoocabon donos ae often hghly dssocated, theeby equng databases fo both feedstocks and the fagments. Fo pedctve modelng, eacton mechansms must be developed fo abtay mxtues and wde anges of pessues. CFDRC_0503_11

39 C 4 F 8, C 2 F 4 CROSS SECTION SETS The fst step n developng a eacton mechansm s complaton of electon mpact coss secton sets. CFDRC_0503_12 Ref: V. McKoy and W. L. Mogan

40 ICP CELL AND [CF 2+ ] FOR C 4 F 8, 10 mto An ICP eacto pattened afte Oehelen, et al. was used fo valdaton. Reacto has a metal ng wth magnets to confne plasma. CF 2+ s one of the domnant ons n C 4 F 8 plasmas due to lage dssocaton. The majo path fo the CF 2+ s: C 4 F 8 + e C 2 F 4 +C 2 F 4 + e C 2 F 4 + e CF 2 +CF 2 + e CF 2 C 4 F 8, 10 mto, 1.4 kw, MHz SRC_2003_AVV_2 + e CF 2+ + e + e

41 [n e ] and T e FOR C 4 F 8, 10 mto Electon densty peaks at cm -3. The peak n T e occus n the skn laye due to collsonless electon heatng by the lage electc feld. T e s athe unfom n the bulk plasma whee electons themalze though e-e collsons. SRC_2003_AVV_3 C 4 F 8, 10 mto, 1.4 kw, MHz

42 I P (PROBE CURRENT) IN ICPs SUSTAINED IN A, O 2 I (ma) Exp. wthout magnets Calc. Exp. wth magnets Calc. o Powe (W) A, 10 mto O 2, 10 mto Magnetc confnement s geneally moe effectve n electonegatve plasmas wth a lage vaety of ons. CFDRC_0503_13

43 I P VERSUS POWER FOR ICPs IN C 4 F 8, A/C 4 F 8, O 2 /C 4 F 8 I (ma) Exp. 10 mto wthout magnets Calc. Exp. wth magnets Calc. C 4 F Powe (W) % O addtve 2 The dffeences n I P wth and wthout magnets nceases wth powe due to nceased non-lnea Loentz foce. I P nceases wth A addton n A/C 4 F 8 compaed to A/O 2 due to hghe dssocaton of C 4 F 8 and lowe electonegatvty. I (ma) % A addtve Exp. A/C F Calc. 4 8 Exp. O /C F Calc W, 20 mto CFDRC_0503_ MHz, -100 V pobe bas.

44 ION COMPOSITION IN C 4 F 8, A/C 4 F 8 Optmzaton of pocessng condtons on, fo example, powe ctcally depends on the composton of the adcal and on fluxes. CFDRC_0503_22 10 mto, MHz

45 EFFECT OF MAGNETS ON [CF + ] Wthout magnets [CF + ] has a maxmum at the edge of the classcal skn depth whee the electon mpact onzaton s the lagest. The statc magnetc felds boaden the poducton of [CF + ] n the adal decton. A/C 4 F 8 =20/80, 3 mto, MHz, 400 W. SRC_2003_AVV_9

46 MERIE REACTOR The model eacto s based on a TEL Desgn havng a tansvese magnetc feld. K. Kubota et al, US Patent 6,190,495 (2001) MJK_GEC02_09

47 TEL-DRM: A / C 4 F 8 / O 2 Wth eacton mechansms developed fo A / C 4 F 8 / O 2 and mpoved ablty to model MERIE systems, paametezatons wee pefomed fo TEL-DRM lke condtons. A / C 4 F 8 / O 2 = 200/10/5 sccm, 40 mto, 1500 W. SRC03_31

48 TEL-DRM: A / C 4 F 8 / O 2 The lage vaety of on masses poduces vastly dffeent IEADs. A / C 4 F 8 / O 2 = 200/10/5 sccm, 40 mto, 1500 W. SRC03_32

49 SURFACE CHEMISTRY (The most ll defned but pehaps most mpotant step.) CFDRC_0503_15

50 SELECTIVITY IN MICROELECTRONICS FABRICATION: PLASMAS AND POLYMERS Fabcatng complex mcoelectonc stuctues made of dffeent mateals eques exteme selectvty n, fo example, etchng S wth espect to SO 2. Monolaye selectvty s equed n advanced etchng pocesses. These goals ae met by the unque plasmapolyme nteactons enabled n fluoocabon chemstes. Ref: G. Tmp UTA_1102_32

51 FLUORCARBON PLASMA ETCHING: SELECTIVITY Selectvty n fluoocabon etchng eles on polyme deposton. Electon mpact dssocaton of feedstock fluoocabons poduce polymezng adcals and ons, esultng n polyme deposton. e + A/C4F8 CFn, M + CFn, M + COFn, SFn CFn, M + SFn CFx Polyme CFx Polyme SO2 S Compound delectcs contan oxdants whch consume the polyme, poducng thnne polyme layes. Thcke polyme on non-delectcs estct delvey of on enegy (lowe etchng ates). ADVMET_1002_04

52 FLUORCARBON PLASMA ETCHING: SELECTIVITY Low bas: Deposton Hgh bas: etchng Etch Rate (SO 2 > S) Polyme Thckness (SO 2 < S) G. Oehlen, et al., JVSTA 17, 26 (1999) ADVMET_1002_05

53 SURFACE KINETICS: FLUOROCARBON PLASMA ETCHING S/SO 2 C x F y passvaton egulates delvey of pecusos and actvaton enegy. Chemsopton of CF x poduces a complex at the oxde-polyme nteface. 2-step on actvated (though polyme laye) etchng of the complex consumes the polyme. Actvaton scales nvesely wth polyme thckness. Etch pecusos and poducts dffuse though the polyme laye. Plasma C x F y Passvaton Laye C x F y F CF 4 CF n CF n I + SFn, CF n CO 2 CF x I +, F CO 2 I +, F SFn In S etchng, CF x s not consumed, esultng n thcke polyme layes. SO 2 SO 2 SO 2 SF x CO 2 SF x UTA_1102_34

54 MONTE CARLO FEATURE PROFILE MODEL (MCFPM) The MCFPM pedcts tme and spatally dependent pofles usng enegy and angulaly esolved neutal and on fluxes obtaned fom equpment scale models. Abtay chemcal eacton mechansms may be mplemented, ncludng themal and on asssted, sputteng, deposton and suface dffuson. Enegy and angula dependent pocesses ae mplemented usng paametc foms. Mesh centeed dentfy of mateals allows bual, ovelayes and tansmsson of enegy though mateals. SCAVS_1001_08

55 Etch Rate (nm/mn) ETCH RATES AND POLYMER THICKNESS Etch ates fo S and SO 2 ncease wth nceasng bas due, n pat, to a decease n polyme thckness. The polyme s thnne wth SO 2 due to ts consumpton dung etchng, allowng fo moe effcent enegy tansfe though the laye and moe apd etchng Expement Model SO Self-Bas Voltage (-V) S Polyme Layes C 2 F 6, 6 mto, 1400 W ICP, 40 sccm λ Polyme SO2 S Self-Bas Voltage (-V) Tansfe Coeffcent (λ) Exp. Ref: T. Standaet, et al. J. Vac. Sc. Technol. A 16, 239 (1998). ADVMET_1002_15

56 POLYMERIZATION AIDS SELECTIVITY Less consumpton of polyme on S elatve to SO 2 slows and, n some cases, temnates etchng, povdng hgh selectvty S Inteface SO Etch Depth (µm) TIME (mn) ADVMET_1002_16

57 TAPERED AND BOWED PROFILES In hgh aspect ato (HAR) etchng of SO 2 the sdewall of tenches ae passvated by neutals (CF x, x 2) due to the boad angula dstbutons of neutal fluxes. PR SO2 Ethe tapeed o bowed pofles can esult fom a non-optmum combnaton of pocessng paametes ncludng: Degee of passvaton Ion enegy dstbuton Radcal/on flux composton. BOWED TAPERED ADVMET_1002_17

58 PROFILE TOPOLOGY: NEUTRAL TO ION FLUX RATIO Pofles depend on ato of polyme fomng fluxes to enegy actvatng fluxes. Small atos poduce bowng, lage atos tapeng. Contollng ths ato though gas mxtue (e.g., A/C 2 F 6 ) enables specfcaton of pofle topology. A/C2F6 = 0/100 20/80 40/60 60/40 Photoesst SO2 Φn / Φon Wb / Wt 4 Φn/Φon A Facton Wb / Wt Φn/Φon= 12 CFDRC_0503_

59 LOW-K DIELECTRICS As featue szes decease and devce count nceases, the damete of nteconnect wes shnks and path length nceases. Lage RC-delay lmts pocesso pefomance. To educe RC-delay, low delectc constant (low-k) mateals ae beng nvestgated. UTA_1102_35 L. Petes, Sem. Intl., 9/1/1998

60 POROUS SILICON DIOXIDE Poous SO 2 (xeogels) have low-k popetes due to the lowe mass densty esultng fom (vacuum) poes. Typcal poostes: 30-70% Typcal poe szes: 2-20 nm Poous SO 2 (P-SO 2 ) s, fom a pocess development vewpont, an deal low-k delectc. Extensve knowledge base fo fluoocabon etchng of conventonal non-poous (NP-SO 2 ). No new mateals (though most P-SO 2 contans some esdual ogancs) Few new ntegaton equements ADVMET_1002_07

61 WHAT CHANGES WITH POROUS SO 2? The openng of poes dung etchng of P-SO 2 esults n the fllng of the vods wth polyme, ceatng thcke layes. Ions whch would have othewse ht at gazng o nomal angle now ntesect wth moe optmum angle. An mpotant paamete s L/a (polyme thckness / poe adus). Adapted: Standaet, JVSTA 18, 2742 (2000) ADVMET_1002_18

62 ETCH PROFILES IN SOLID AND POROUS SO 2 Poous SO 2 s beng nvestgated fo lowpemttvty delectcs fo nteconnect wng. In polymezng envonments wth heavy sdewall passvaton, etch pofles dffe lttle between sold and poous slca. UTA_1102_36 Poston (µm) Sold Poston (µm) Poosty = 45 % Poe adus = 10 nm The open sdewall poes quckly fll wth polyme. ANIMATION SLIDE

63 ETCHING OF POROUS SO 2 Etch ates of P-SO 2 ae geneally hghe than fo non-poous (NP). Examples: 2 nm poe, 30% poosty 10 nm poe, 58% poosty Hghe etch ates ae attbuted to lowe mass densty of P-SO 2. CHF 3 10 mto, 1400 W Exp: Oehlen et al. Vac. Sc.Technol. A 18, 2742 (2000) ADVMET_1002_23

64 PORE-DEPENDENT ETCHING To solate the effect of poes on etch ate, coected etch ate s defned as Etch Rate (ER) p = poosty If etchng depended only on mass densty, coected etch ates would equal that of NP- SO 2. 2 nm poes L/a 1 : C-ER > ER(SO 2 ). Favoable yelds due to non-nomal ncdence may ncease ate. 10 nm poes L/a 1 : C-ER < ER(SO 2 ). Fllng of poes wth polyme decease ates. ADVMET_1002_24 coected = ER egula (1- p), Etch Rate (nm/mn) C - Coected C-2 nm Non poous C-10 nm Self Bas (V)

65 EFFECT OF POROSITY ON BLANKET ETCH RATES Etch Rate (nm mn -1 ) ~ Regula Coected 2 nm poes Poosty (%) Etch Rate (nm mn -1 ) Regula Coected 10 nm poes Poosty (%) 2 nm poes: Etch ate nceases wth poosty. 10 nm poes: Polyme fllng of poes educes etch ate at lage poostes. ADVMET_1002_25

66 OXYGEN PLASMA CLEANING OF POLYMER Afte etchng, the polyme must be emoved fom the featue. O 2 plasmas ae typcally used fo polyme stppng, usually dung photoesst mask emoval. Unlke hydocabon polymes whch spontaneously eact wth O, fluoocabon polymes eque on actvaton fo etchng. Polyme + Enegetc Ion Actvated Polyme Ste (P*) P* + O Volatle Poducts Removal of polyme fom poous mateals s dffcult due to shadowng of on fluxes caused by the poe mophology. UTA_1102_38

67 EFFECT OF PORE RADIUS ON CLEANING 1.0 Facton of Resdual Polyme nm Tme (Ab Unts) Lage poes ae moe dffcult to clean due small vew angle of on fluxes. Lowe fluxes of less enegetc ons educe actvaton and lengthen cleanng tme. UTA_1102_39 ANIMATION SLIDE 4 nm 16 nm

68 TOWARDS INTEGRATED PROCESS MODELING (The last step metal deposton.) CFDRC_0503_17

69 IONIZED METAL PHYSICAL VAPOR DEPOSITION (IMVPD) IMPVD s a technque to depost seed layes and bae coatngs, and fll tenches. A flux of both neutal and metal atoms moe unfomly poduce depostons wthout fomaton of vods. CFDRC_0503_18

70 Cu IMVPD: REACTOR SCALE MODELING CFDRC_0503_19 40 mto A 1 kw ICP 0.3 kw Magneton -25 V bas

71 EFFECT OF PORE RADIUS ON Cu DEPOSITION Suogate study fo seed laye deposton and bae coatng. Vods ae ceated at the poe suface o ntated due to the pesence of poes. NP SRC03_AS_17 4 nm 10 nm 16 nm ANIMATION SLIDE Pesence of vods ae ponounced fo bgge poes.

72 MERIE Fluoocabon plasma etchng of poous SO 2 26 SOLENOID DOME ICP O 2 plasma cleanng of PR and polyme. HEIGHT (cm) 0 GAS INJECTORS BULK PLASMA f BIASED SUBSTRATE WAFER COILS PUMP PORT RADIUS (cm) s POWER SUPPLY s POWER SUPPLY IMPVD of Cu seed laye CFDRC_0503_22

73 MERIE: ION FLUXES AND ENERGIES Ion Fluxes (cm -2 s -1 ) C 2 F + 4 (10 15 ) A + (10 16 ) C 3 F 5 + (10 15 ) CF + (10 14 ) CF 3 + (10 14 ) Radus (cm) Ion Enegy (ev) CF + A + C 2 F Ion Angle A/O 2 / C 4 F 8 = 200/5/10 sccm 2000 W 40 mto CFDRC_0503_23 Due to hgh dluton and low factonal dssocaton, domnant ons ae A +, C 2 F 4 +

74 MERIE: POROUS SO 2 ETCH Moe apd etchng wth poous SO 2 esults n less mask eoson and bette pofle contol, but moe polyme fllng of poes. CFDRC_0503_24

75 ICP: POROUS SO 2 AND PHOTORESIST CLEAN Longe cleanng tmes ae equed wth moe poous mateals to emove polyme whch s shaded fom on flux. CFDRC_0503_25

76 IMPVD: Cu SEED LAYER DEPOSITION Thcke seed layes ae equed wth lage poes to cove ove (o fll) gaps esultng fom open stuctues. CFDRC_0503_26

77 CONCLUDING REMARKS Integated plasma pocess modelng eques addessng a wde ange of physcal phenomena. The lage vaety of gas mxtues, eacto geometes, plasma souces and mateals motvates development of genealzed modelng platfoms wth few a po assumptons. The fundamental modelng challenges ae no dffeent than n expemental ntegaton: If a sngle module (pocess) s valdated (optmzed) n solaton, wll t stll be vald (optmum) when ntegated wth othe steps? CFDRC_0503_20

78 ACKNOWLEDGEMENTS D. Alex V. Vasenkov D. Gottleb Ohelen M. Avnd Sankaan M. Pamod Subamonum Fundng Agences: 3M Copoaton Semconducto Reseach Copoaton Natonal Scence Foundaton SEMATECH CFDRC Inc. CFDRC_0503_21