1. Atomic, Molecular and Optical Data requirements for plasma processing 20 th ESCAMPIG, Novi Sad, July 13 – 17, 2010 Nigel Mason The Open University UK

2. Workshop on data needs for plasma physics Session to discuss fundamental processes and applications in plasma processing This talk will review our knowledge of the fundamental processes Discuss what we know and what we don’t know. and comment on the critical need for DATA BASES

3. ESCAMPIG 2010 At this meeting a wide range of plasmas will be discussed.

4. Technological plasmas in semiconductor industry, CVD, magetrons and pollution abatement

5. Related to Nanotechnology

6. Biophysics and medical applications

7. Plasmas cover a wide range Divide into three categories; Low pressure Atmospheric plasma Fusion plasma

8. However, in order to understand all of these, we require knowledge of the fundamental processes – physical and chemical !

9. So how do we collect such data ?

10. Look at the plasma !

11. So how do we collect such data ? Look at the plasma ! Optical spectroscopy (and IR and UV !)

12. So how do we collect such data ? Optical Spectroscopy Identify chemical species; May gain knowledge of Gas Temperature; Electron Temperature E fields (U Czarnetski and S Hamaguchi CARS for atmospheric pressure plasmas)

13. Optical Spectroscopy What data do we need ? Absorption spectra Emission spectra Einstein coefficients but also …

14. OpticalSpectroscopy What data do we need ? Branching ratios (cascade) Stark & Doppler broadening Temperature dependence Quenching rates

15. Optical Spectroscopy What data do we need ? And what we cant measure (easily) Dark states (forbidden transitions) Short lived radicals Dust Anions

16. So how do we collect such data ? Charged species Electrons Ions

17. Electrons Measure electron flux and temperature Langmuir probe Thompson Scattering Some problems in reactive/corrosive gases And limited temporal resolution

18. Ions Measure ion flux and composition Measure ion mobility – not distinct Mass spectrometry – hard to do in situ. fragmentation patterns, kinetic energy effects (radicals ?)

19. Dynamics and Chemistry Need to build models/simulations to test observations

20. Dynamics and Chemistry Need to build models/simulations to test observations Only as good as data you put into them (even if you know the physical parameters)

21. Ideal is to have the ‘Virtual factory’

22. Plasma modelling and database assessment

24. What data is needed ?

25. Plasma modelling and database assessment What data is needed ? Electron impact processes Energy resolved cross sections Average temperature dependent rate coeffs Dissociation/ionisation processes (including DEA, DR) Collisions with fragments (eg CF 3 and CF 2 ) Emission cross sections for diagnostics SURFACE REACTIONS

26. Plasma modelling and database assessment So how good is the data base ?

27. So where are we now in electron studies ? Electron – atom scattering Really quite good now at least for light atoms Elastic, excitation (including resonances) Ionisation

28. Elastic Scattering - rare gases Cho, McEachran, Tanaka, Buckman JPB 37 4639 (2004)

29. So where are we now in electron studies ? Electron –molecule interactions Very poor c.f. atoms Difficulty is complexity of target New processes – dissociation – drives chemistry

30. So where are we now in electron studies ? Electron –molecule interactions Total cross sections; Accurate to some 5% (allow for forward scattering) Lowest energies few meV !

31. Total cross sections for electron scattering Szmytkowski and collaborators

32. So where are we now in electron studies ? Electron –molecule interactions Elastic cross sections; Accurate to some 10% - good standards Angular range – can now measure 0 to 180 So momentum transfer cross section data are improving

33. Elastic scattering - H 2 O Cho, Park, Tanaka, Buckman JPB 37 625 (2004)

34. So where are we now in electron studies ? Electron –molecule interactions Inelastic cross sections; Vibrational (but resolution and deconvolution) Excitation – very poor despite importance Transmission effects Rotational excitation…

35. Vibrational excitation Energy loss spectra

36. Vibrational excitation - HCOOH

37. So where are we now in electron studies ? Electron –molecule interactions Ionisation; Better data sets (cf Theory – Kim (BE) and Deutsch Maerk ) But Kinetic effects in products

38. Dissociative Electron Attachment (DEA) Production of Negative Ions in Plasmas ABC + e - ABC # - A (*) - + BC A (*) - + B + C Resonance  ~ 10 -14 s So where are we now in electron studies ?

39. Negative ions in plasmas Many commercial plasma/etchant gases are electronegative E.g. The fluorocarbons, chlorine and oxygen (H 2 in fusion plasmas) Negative ions may be major negative charge carrier (> ‘free‘ electron flux) e.g. in CF 4 and oxygen plasmas 10x electron

40. So where are we now in electron studies ? Dissociative Electron Attachment – Question as to how establish cross section Few/no standards Kinetic effects in products Zero energy peaks !

41. So where are we now in electron studies ? Electron –molecule interactions Dissociation to neutrals particularly radicals Ground state products – in its infancy Still testing methodologies No standard Kinetic effects in products

42. So where are we now in electron studies ? Electron –molecule interactions Dissociation to excited states Fluorescence– lots of data but Detector calibrations Role of cascade Kinetic energy – Doppler broadening

43. Summary electron molecule database Lots of data But few complete and self consistent datasets (N2 best --- Loureiro) Need to bring database together and cross reference. Combine expt with theory on-line calcns (Quantemol J Tennyson) Emol database under development

44. What about other processes ? Ion molecule and Neutral reactive chemistry Similar problems Reported rate coefficients may differ by orders of magnitude, depends on temperature, pressure (three body effects)

45. What about clusters ? Important in atmospheric pressure plasmas Particularly the role of water/humidity ! Indeed key role in atmospheric discharges (Kushner Bubbles and biological systems)

46. 12.09.2015 Mass analysis of ions in atmospheric plasma (Hiden)

47. Mass analysis of ions in atmospheric plasma --- coronal discharge in air All are clusters no monomers

50. So cluster chemistry dominates ! And key role of water !!! Anions made by dissociative electron attachment to molecular oxygen O - in region near wire (glow region) and O 2 - in drift region

51. So cluster chemistry dominates ! And key role of water !!! Clusters formed Anions cluster to water molecules easily

52. What about surfaces ? Introduce role of heterogeneous chemistry

53. Characterisation of surface processing Effects of Plasma Processing Parameters on the Surface Reactivity of OH(X2Π) in Tetraethoxysilane/O 2 Plasmas during Deposition of SiO 2 K. H. A. Bogart, J. P. Cushing and R. Fisher

54. Surface Processes Surfaces exposed to plasmas experience bombardment by energetic ions, electrons, neutrals, and photons. The detail in which we understand the effects of such bombardment varies widely depending on the particular process. The goal of fundamental surface studies, both theoretical and experimental, should be to provide insight and data for process simulation and/or reactor design. Examples of the data needed are cross sections and rate constants for energy transfer, reaction, emission, surface diffusion, implantation, reflection, disordering, and recombination. All these processes affect material properties, and all are affected by exposure to the non equilibrium, low-energy plasma. http://www.nap.edu/openbook.php?record_id=1875&page=R11

55. Open Questions Surface studies How to define a cross section on a surface Role of molecular orientation Role of morphology Shift in energy levels and electronic states !

56. Water ice Note : Blue shift in the solid phase

57. Comparison of gas and solid phase Methylamine Note absence of low lying bands in solid phase

58. Sputtering For physical sputtering and energy transfer, the most important properties of the projectile and target are their masses and their interaction potentials. This relative simplicity combined with a wealth of experimental data on sputtering has facilitated the development of sophisticated theories and simulation tools.

59. Etching feature characterisation An understanding of the transfer of energy between surface and ion and the modification of the sidewall surface is needed to model the feature profile and to predict the dependence of etch and deposition rates on microstructure. Little is known about the surface chemistry and physics at atmospheric pressure and high temperature (greater than 800°C), which are typical conditions for rapid deposition of diamond and superconducting films.

60. Beam Surface Experiments Much of our fundamental understanding of surface processes occurring during etching and deposition comes from well-controlled plasma simulation experiments in which beams of ions, electrons, neutrals, and photons are directed either at well- characterized surfaces. The beams are typically analyzed using mass spectrometry. The surface chemistry is usually diagnosed using XPS, AES etc

61. Published in: K. H. A. Bogart; J. P. Cushing; Ellen R. Fisher; J. Phys. Chem. B 1997, 101, 10016-10023. DOI: 10.1021/jp971596o Copyright © 1997 American Chemical Society

62. Synergy of ion and neutral chemistry Experiments have clearly demonstrated synergy between ion bombardment and neutral chemistry in plasma etching The etching rate with combination of ion and reactive neutrals exceeds the sum of the individual etch rates for ion sputtering and neutral reaction.

63. Extending surface studies Beam-surface studies have been focused largely on etching reactions, But there is perhaps an even greater need for experimental simulation of plasma deposition processes. E.g. diamond and diamond-like film deposition from methane and other hydrocarbon plasmas. With appropriate free radical and ion beams, sticking probabilities are key data

64. What about sticking coefficients ? Method to Determine the Sticking Coefficient of O 2 of Deposited Al During Reactive Magnetron Sputtering, Using Mass Spectrometry W P. Leroy, S Mahieu, R Persoons, D Depla (2009) Plasma Processes and Polymers 0.1002/ppap.200932401 Coefficient of 0.107 ± 0.032 for O 2 on deposited aluminium during reactive magnetron sputtering. Mass spectrometry used to measure local, effective O 2 partial pressure during sputtering, combined with electron probe microanalysis of the oxygen content in deposited layers, we calculate the sticking coefficient.

65. Chemical surface transformations using electron induced reactions/ DEA produces products that subsequently react on the surface E.g. Irradiate film of NF 3 and CH 3 Cl Form CH 3 F Electron Induced surface chemistry

66. e-e- F-F- CH 3 Cl CH 3 F Cl-

67. Basic e - -molecule interactions Resonances E 0 dependence Control via e - -induced chemistry developing electron lithography e - -induced chemistry Cross sections Typical reactions and products Reaction sequences Surface functionalization Reactions at the interface of materials Modification of materials properties - structural - electrical - permeability - optical

68. Anions and dust/aerosol formation ? Anions are known to be precursors of dust formation in plasmas (eg fluorocarbon plasmas etching Silicon wafers) or in silane plasmas but we k now little on heterogeneous chemistry on dust Key to Titan aerosol chemistry ?

69. So how to assemble necessary databases ? Vital but How is it assembled and updated ? How is data selected ? Who pays ? One data base or several ?

70. Any database must fulfill several basic pre-requisites. It should be comprehensive with a full listing of experimental and, where applicable, theoretical results. Often it is assumed that the most recent results are the most accurate – this is often not the case since often both experimentalists and theoreticians publish ‘ calibration data ’ when designing new apparatus/codes. This data is used to illustrate the general operational performance of their system prior to conducting research on new systems. Such ‘ calibration data ’ is seldom of the same rigorous quality as the original data against which it is compared Replacing such ‘ calibration data ’ in a data base for older data is therefore often a mistake and is not the intention of the authors.

71. Any database must fulfill several basic pre-requisites. Any database that aims to be adopted by an applied community should include a list of recommended values. These may be subject to compilers ’ bias (often the choice of which data set to adopt is a question of ‘ gut feeling ’ based on the experience and personal knowledge of the authors providing the data). Therefore it is necessary to have some method by which databases may be compared with one another.

72. Summary of database needs Develop database that community has ownership of Access is easy for posting data Discussion is easy ! Provides up to date summary of data and recommendations

73. VAMDC is funded under the “Combination of Collaborative Projects and Coordination and Support Actions” Funding Scheme of The Seventh Framework Program. Call topic: INFRA-2008-1.2.2 Scientific Data Infrastructure. Grant Agreement number: 239108.

74. VAMDC will provide a scientific data e-infrastructure enabling easy access to A+M resources Http://www.vamdc.org/

75. Virtual Atomic and Molecular Data Centre (VAMDC) aims to build a secure, documented, flexible and interoperable e- science environment-based interface to the existing AM data. The VAMDC will be built upon the expertise of existing AM databases, data producers and service providers with the specific aim of creating an infrastructure that is easily tuned to the requirements of a wide variety of users The project will cover the building of the core consortium, the development and deployment of the infrastructure and the development of interfaces to the existing AM databases as well as providing a forum for training potential users

76. VAMDC does not collect or commission data but… Will be a ‘one stop shop’ access to databases (currently some 17 are planned) Wants to know what data is needed and the format it is most usefully presented in ; hence supports these meetings and discussions WHAT DO YOU NEED ? Survey will follow this meeting !

78. Brussels -Negociation - S1 - 23/01/2009 VAMDC - Brussels - Nov 08

79. Brussels -Negociation - S1 - 23/01/2009 Main Objectives Atomic & Molecular data underpins a wide range of basic and applied research and industrial development VAMDC will provide the extensible scientific data infrastructure enabling cost effective, European wide access to the increasingly large, distributed and complex A+M resources VAMDC will provide flexible interfaces to A+M resources supporting improved producer/consumer linkages Existing European wide grid (EGEE), network (GEANT) and application (Euro-VO) infrastructures form the effective baseline platform to create the VAMDC infrastructure VAMDC will extend these infrastructures to support common access to A+M data thus placing this primary data at the heart of the scientific progress

80. Brussels -Negociation - S1 - 23/01/2009 Main Objectives of the Proposal We will deliver an electronic infrastructure which is general, flexible and useful for collecting and accessing A&M data. In order to demonstrate those properties we will: implement VAMDC interface for accessing major existing databases containing heterogeneous data and aimed at different users demonstrate data queries across multiple DBs that are focussed on specific research topic(s) demonstrate data publishing/quality control process for major A&M data producers involve wide user and producer communities in those test applications of VAMDC

81. Funding 3 million Euros for 42 months from July 1 st 2009 to develop this data base Meetings with major user communities will be held (including the plasma community) Operational and sustainable by end of project