Presentation is loading. Please wait.

Presentation is loading. Please wait.

Development of Multi-scale Methodology of High-k oxides Growth

Similar presentations


Presentation on theme: "Development of Multi-scale Methodology of High-k oxides Growth"— Presentation transcript:

1 Development of Multi-scale Methodology of High-k oxides Growth

2 Outline PART 1: Introduction and context PART 2:
First principles investigations of possible growth mechanisms PART 3: Lattice based kinetic Monte-Carlo algorithm (HfO2) PART 4: Exploitation, validation and results

3 Introduction and context
PART 1 Introduction and context High-k oxides: Why? How? Methodology: available approaches overview Multi-scale strategy Our goal: first predictive and generic kMC tool for high-k oxides deposition (ALD first steps, kinetics, process optimization…)

4 Enjeu majeur de la modélisation et de la simulation:
Cfontexte: Croissance d’oxyde à fortes permitivité (high-k) Miniaturisation Nanotechnologie Nouvelles filières Nouveaux matériaux Enjeu majeur de la modélisation et de la simulation: Simulation des structures d’interfaces

5 Simulation des structures d’interfaces
Why high-k oxides ? MOSFET evolution: “scaling” ITRS 2004 Production year Etching width Gate oxide thickness 1997 250 nm 4 – 5 nm 1999 180 nm 3 – 4 nm 2001 150 nm 2 – 3 nm 2002 130 nm 2004 90 nm < 1.5 nm 2007 65 nm < 0.9 nm 2010 45 nm < 0.7 nm Intel Corp. Enjeu majeur de la modélisation et de la simulation: Simulation des structures d’interfaces

6 Why high-k oxides ? To extend Moore’s Law
Problem: high leakage current through the gate. A solution: use a gate oxide of greater permittivity than SiO2. Oxide k SiO2 3,9 Al2O3 ~ 9,8 ZrO2 ~25 HfO2 ~35 Intel Corp.

7 État actuel: Limite physique de l’oxyde du silicium SiO2
Les oxydes minces État actuel: Limite physique de l’oxyde du silicium SiO2 Oxydes candidats Problèmes spécifiques: Stabilité vis-à-vis du silicium Nature et contrôle de la couche d’interface Stabilité de la microstructure Mener un travail de recherche en amont Nouveaux procédés du dépôt Contrôle à l’échelle nanométrique Caractérisation structurale et électrique Coupler: recherches expérimentale & théorique

8 High-k oxides implementation into microelectronics
Materials properties considerations High permittivity Sufficient band offset (to minimize leakage) Low fix charges density (for reliable threshold voltage) Low interface states density (to keep an acceptable mobility in the channel) Low dopant diffusivity (to keep them in the electrode or the channel) Limitation of SiO2 regrowth (which would reduce the capacitance) Amorphous phase or at least few grain boundaries (to minimize leakage) Process considerations Known solution for the gate electrode High-k oxide deposition process compatibility (with other materials, with industrial needs) High-k oxide (itself) compatibility with other CMOS processes (e.g. crystallization problems, dopant diffusivity) Reproducibility Reliability

9 High-k oxides implementation into microelectronics
Process choice: Atomic Layer Deposition (ALD) Phase 1 : Precursor pulse Phase 2 : Precursor purge Phase 3 : Water pulse Phase 4 : Water purge (…)

10 Methodology: available approaches overview
Available experimental data: IR spectroscopy, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), low energy ion scattering (LEIS)… + Macroscopic simulations: feature scale and reactor scale.

11 Oxydes de grille : Stratégie
L’ALD implique des systèmes à états multiples, hors équilibre, des dynamiques non linéaires (par bifurcations). La complexité du problème exige une stratégie multi-échelle. Nanoscopique Ab initio / DFT / DM Mesoscopique MCC Macroscopique Expérimentation Dizaines d’atomes Plusieurs millions d’atomes Expérimentation Technologie… Morphologie, Composition Taux de croissance… Mécanismes réactionnels structures géométriques & électroniques… Notre but : la description des mécanismes physico-chimiques principaux aux échèles nano et meso du dépôt par ALD 11

12 PART 2 Ab initio Calculations of reaction paths during the initial stage of ALD growth of HfO2 Approach: cluster-based DFT *Reactions between the precursors and hydroxylated surface: 1) Decomposition of HfCl4 on the surface 2) Hydrolysis *Particle formation and Chlore Contamination mechanisms

13 Apport de la Modélisation depuis 2002
Les groupes OH sont considérés les sites actifs principaux de la surface (exp.) Mécanismes de base : Addition des ligands à la surface – Musgrave, Elliott, Gavartin, Raghavachari, Jeloaica Echange des ligands avec la surface – Musgrave, Jeloaica, Dkhissi Hydrolyse – Musgrave, Elliott, Jeloaica, Dkhissi Effets de coopérativité – Jeloaica, Dkhissi Contamination/Diffusion (Cl, C, N, H…) - Musgrave, Jeloaica, Dkhissi (non publié) Diffusion de l’Oxygène dans le substrat – non publié 13

14 DFT : elementary mechanisms
Single bond on SiO2 - Incorporation is an endothermic reaction - HCl stays on the surface => purge phase {SiO2}-OH + HfCl4  {SiO2}-O-HfCl3 + HCl Initial reaction pathway and associated barriers in the case of Hf-based precursor exposure on SiO2/Si(100)

15 DFT : elementary mechanisms
Double bond on SiO2 {SiO2}-(OH)2 + HfCl4  {SiO2}-O2-HfCl HCl, 0,29eV 0.17 0,23eV 0,12eV 0.53 0,02eV 0.50 0.52 -0,25eV 0.15 Des calcules quantiques on détermine les mécanismes élémentaires gouvernants les réactions chimiques qui se déroulent durant les différentes phases du dépôt, les configurations atomistiques ainsi que les barrières d’activation qui leurs sont associés. voici un exemple de mécanisme réactionnel que nous avons déterminé dans notre étude par calcul ab initio que je ne détaillerais pas par manque de temps. Je tiens juste a préciser que chaque mécanisme élémentaire peu se dérouler dans un sens ou dans l’autre ce qui traduis la réversibilité du système. Par exemple au mécanisme élémentaire d’adsorption du précurseur on associe le mécanisme opposé de désorption de ce précurseur. -0,40eV -0,50eV - Desorption is as favourable as the first bond formation - Both bond formation are endothermic reaction - Dense structure of the oxide 15 15

16 DFT : hydrolyse d'une liaison Hf--Cl
DFT : elementary mechanisms DFT : hydrolyse d'une liaison Hf--Cl 0.619 0.12 0.916 {SiO2}-O-HfCl3 + H2O  {SiO2}-O-HfCl2(OH) + HCl - La désorption de l'eau est plus favorable que hydrolyse - Hydrolyse est une réaction endothermique 16 16

17 DFT : elementary mechanisms
Hydrolysis, solvatation effect 17

18 DFT : elementary mechanisms
Chlore contamination

19 DFT : elementary mechanisms
Particle formation: MnO2n structure size A. DKHISSI ,

20 Lattice based kinetic Monte-Carlo algorithm (HfO2)
PART 3 Lattice based kinetic Monte-Carlo algorithm (HfO2) Preliminary considerations: space and time scales Lattice based model: how the atomistic configuration is described Temporal dynamics: how the atomistic configuration changes Elementary mechanisms: some examples

21 ≈ ≈ Preliminary considerations:
Space scale: Crystallographic considerations

22 Preliminary considerations:
Time scale: simulation algorithm choice TIME CONTINUOUS KINETIC MONTE-CARLO Attainable phenomenon duration: second Realistic evolution Monte-Carlo steps have time meaning

23 Conventional HfO2 cell on substrate Discrete locating model
Lattice based model Merging different structures into one framework Conventional HfO2 cell on substrate Discrete locating model Si (layer k=1) Hf (k=2 and even layers) Ionic oxygen (k + 1/2) Hf (k=3 and odd layers) 2D cell

24 Lattice based model Other aspects: strands, contaminants…
Example: non-crystalline HfCl3 group, bound to the substrate via one oxygen atom. Non-crystalline aspects: Non-crystalline Hf Non-crystalline O OH strands Cl strands HCl contamination H2O

25 Lattice based model Substrate initialization (example)
Si (100) layer (k=1) + User defined OH and siloxane distributions (random) = Large variety of available substrates

26 Lattice based model Zhuravlev model for substrate initialization
From the Monte-Carlo point of view, OH density is the percentage of sites that have an OH

27 Temporal dynamics Mechanisms and events (definitions)
Mechanism = elementary reaction mechanism with associated activation barrier E≠ Site = one cell within the lattice, located by (i,j,k) indexes and containing occupation fields (can be empty) Event = Mechanism + Site, (depending on the local occupation, can be possible or not, thus must be “filtered”)

28 kMC: Temporal Dynamics
Events occurrence times calculation Occurrence time of event « mechanism m on site (i,j,k) » : where Z is a random number between 0 and 1 Maxwell-Boltzmann statistics derived acceptance for arrival mechanisms (1-precursor and 2-water): Arrhenius law derived acceptance with attempt frequency ν for all other mechanisms:

29 Occurrence of the event of smallest occurrence time
Temporal dynamics Summary: the kinetic Monte-Carlo cycle Occurrence times calculation and comparison Atomistic configuration change Events filtering Occurrence of the event of smallest occurrence time

30 Temporal dynamics ALD cycle + kMC cycle
As the kMC cycle works, ALD parameters change periodically: Phase 1 : Precursor Pulse - duration T1 - temperature Th1 -pressure P1 Phase 2 : Precursor Purge - duration T2 - temperature Th2 Phase 3 : Water Pulse - duration T3 - temperature Th3 - pressure P3 Phase 4 : Water Purge - duration T4 - temperature Th4

31 Mechanisms (some examples)
HfCl4 adsorption (from DFT) E≠ = 0 eV ΔE = eV

32 Mechanisms (some examples)
Dissociative chemisorption (from DFT) E≠ = 0.88 eV ΔE = 0.26 eV

33 Mechanisms (some examples)
Densification mechanisms purpose

34 Mechanisms (some examples)
Densification: interlayer non-cryst./cryst. (from kMC)

35 Mechanisms (some examples)
Densification: multilayer non-cryst./tree (from kMC)

36 Mechanisms: complete list
01 MeCl4 adsorption 02 H2O adsorption 03 MeCl4 Desorption 04 HCl Production 05 H2O Desorption 06 Hydrolysis 07 HCl Recombination 08 HCl Desorption 09 Dens. Inter_CI_1N_cOH-iOH (all k) 10 Dens. Inter_CI_1N_cOH-iCl (all k) 11 Dens. Inter_CI_1N_cCl-iOH (all k) 12 Dens. Inter_CI_2N_cOH-iOH (all k not2) 13 Dens. Inter_CI_2N_cOH-iCl (all k not2) 14 Dens. Inter_CI_2N_cCl-iOH (all k not2) 15 Dens. Intra_CI_1N_cOH-iOH (k=2) 16 Dens. Intra_CI_1N_cOH-iCl (k=2) 17 Dens. Intra_CI_1N_cCl-iOH (k=2) 18 Dens. Intra_CC_1N_cOH-cOH (k=2) 19 Dens. Intra_CC_1N_cOH-cCl (k=2) 20 Dens. Intra_CC_2N_cOH-cOH (k=2) 21 Dens. Intra_CC_2N_cOH-cCl (k=2) 22 Dens. Bridge_TI_2N_tOH-iOH (k=2) 23 Dens. Bridge_TI_2N_tOH-iCl (k=2) 24 Dens. Bridge_TI_2N_tCl-iOH (k=2) 25 Dens. Bridge_TI_3N_tOH-iOH (k=2) 26 Dens. Bridge_TI_3N_tOH-iCl (k=2) 27 Dens. Bridge_TI_3N_tCl-iOH (k=2) 28 Dens. Bridge_TC_3N_tOH-cOH (k=2) 29 Dens. Bridge_TC_3N_tOH-cCl (k=2) 30 Dens. Bridge_TC_3N_tCl-cOH (k=2) 31 Dens. Bridge_TC_4N_tOH-cOH 32 Dens. Bridge_TC_4N_tOH-cCl 33 Dens. Bridge_TC_4N_tCl-cOH 34 Dens. Bridge_TT_3N_tOH-tOH (k=2) 35 Dens. Bridge_TT_3N_tOH-tCl (k=2) 36 Dens. Bridge_TT_4N_tOH-tOH 37 Dens. Bridge_TT_4N_tOH-tCl 38 Dens. Bridge_TT_5N_tOH-tOH 39 Dens. Bridge_TT_5N_tOH-tCl 40 Siloxane Bridge Opening Suggested by… -DFT studies -kMC investigation -Experiments

37 Exploitation, validation and results
PART 4 Exploitation, validation and results Hikad simulation platform ALD first steps Growth kinetics

38 Hikad simulation platform
Main features HfO2, ZrO2 and TiO2 ALD ALD thermodynamic parameters (link with experimental data) Start from an existing atomistic configuration file (Recovery option) Initial substrate atomistic configuration customization Feedback options (log file + automatic configuration/graphic files export) Back up option Evolutivity Steric restriction switch (for big precursors) Mechanisms activation energies Performance Huge substrates compared to ab initio or DFT Up to 1015 events Improved events filtering (SmartFilter option) Shortcuts method preventing fast flip back events (SmartEvents option) Computation effectiveness analysis Analysis Simulation data analysis, even during simulation job Easy and fast browsing through events using bookmarks (find event, ALD phase, ALD cycle...) Atomistic configuration visualisation using AtomEye Snapshots (jpeg, ps or png formats) Configuration analysis (substrate, coverage, coordination...) Batch processing

39 ALD first steps Coverage vs. substrate initialization

40 ALD first steps Coverage vs. substrate initialization
One precursor pulse phase: 100ms, 1.33mbar, 300°C Best start substrates: 50% and Random on dimers

41 ALD first steps Early densifications barrier fit
One precursor pulse phase: 90% OH, 200ms, 1.33mbar, 300°C Criteria: 90% OH => 80% coverage (exp.) => Densifications barriers: 1.5 eV

42 ALD first steps Coverage vs. Deposition temperature
Precursor pulse phase: 50ms, 1.33mbar + purge -Low temperatures: chemisorptions can’t occur -High temperatures: poor OH density => Optimal temperature: 300°C

43 ALD first steps Surface saturation One precursor pulse phase:
1.33mbar, 300°C Saturation: 48% coverage for a 90ms long pulse

44 Growth kinetics Coverage for 10 ALD cycles
Pulse phases: 1.33mbar, 300°C + purges Fast first cycle, then slow growth… 73% coverage saturation = simulation artefact

45 Growth kinetics End configuration
-First layer will never be full nor dense: bridge densifications needed -Hard to achieve 100% substrate coverage, “waiting” for SiOSi openings -“Blocking states” are visible (“trees”)

46 Growth kinetics: speeds
Hard to obtain a reliable and stable growth speed because of blocking effect Steady state regime simulations suffer less Transient regime Steady state regime Vt,exp = 7E+13 Hf/cm²/cycle (TXRF) Vs,exp = 12E+13 Hf/cm²/cycle (TXRF)

47 Growth kinetics: conclusions
ALD cycle Transient regime (Vt) “Waiting” for siloxane bridges openings until full SiO2 coverage. Steady state regime (Vs>Vt) HfO2 growth onto HfOx(OH)y (more OH) Amount of deposited Hf atoms 1st cycle Fast initial Si-OH sites saturation

48 Conclusion Original methodology: - Multi-scale strategy
- First predictive tool at these space and time scales for high-k oxides growth - Generic method: MeO2 oxides (changing barriers), other precursors (using steric restriction switch) Validation and first encouraging results: - Substrate preparation dependence - Optimal growth temperature - Surface saturation - Activation barriers calibration (densifications) - Growth kinetics: hard substrate coverage, but “blocking effect”

49 Perspectives… First: - Reduce blocking effect with new densification mechanisms - Add migration mechanisms, and lateral growth mechanisms to obtain complete substrate coverage and maybe grain boundaries - Study coordination evolution and crystallisation Next: - Simulate thermal annealing (migrations, crystallisation…) - Dopant migration - Standardisation

50 Electronic structure of poly(9,9-dioctyfluorene)
in the pristine and reduced state The electronic structure of the conjugated polymer poly(9,9-dioctylfluorene) and the charge storage mechanism upon doping with lithium atoms have been studied using a combined experimental-theoretical approach. Experimentally, the density of states in the valence band region was measured using ultraviolet photoelectron spectroscopy, and the spectra interpreted with the help of the results of ab-initio calculations

51 Chemical structures of PFO, LPPP and PPP

52 Electronic structure of poly(9,9-dioctyfluorene)
in the pristine state UPS spectra of the valence band region of PFO: The He II radiation (white dots) and synchrotron radiation (black dots) spectra are compared with the theoretical DOVS. The bottom panel shows the corresponding VEH band structure. He UPS spectrum showing the two lowest binding energy features of pristine PFO. Excellent agreement between theory and experiment

53 Comparison between PFO with PPP and LPPP
Comparison of the He I UPS spectra of PFO with PPP and LPPP: experimental spectra and theoretical DOVS VEH theoretical band structures of PFO, LPPP, and PPP.

54

55 Electronic structure of poly(9,9-dioctyfluorene)
in the reduced state Comparison of the VEH theoretical simulations with the experimental results UPS spectra illustrating the doping-induced changes in the valence band region of PFO as a function of Li deposition. Starting from the bottom spectrum ~corresponding to the pristine polymer!, succeeding spectra correspond to increases in lithium deposition. The overall changes in the VB region are displayed in the left panel. The right-hand side provides a magnification of the region close to the Fermi energy.


Download ppt "Development of Multi-scale Methodology of High-k oxides Growth"

Similar presentations


Ads by Google