Surface Engineering PJM1

Surface Engineeringwith Ion Beams and Plasma Jets

Plasma Source

Optic

Axel Schindler and Thomas ArnoldLeibniz Institute of Surface Modification, Leipzig, Germany www.iom-leipzig.de

Leibniz-InstitutfrOberflchenmodifizierung

ManufacturingTechnologies to Support Large Science ProjectsParis, France 25th - 26th November 2010 1

Leibniz-Institute for Surface Modification - IOM -

Field of work:

NonThermalModificationofSurfacesand Thin Films andThin Film DepositionWith the help ofElectron-, Ion-, Plasma- and UV-Photon-Beams

Staff:48 permanent~ 90 in projects (2..3 y.)

~ 140 employees in total

Annualbudget:~ 6 Mio. Basic Financing

+ ~ 3...5 Mio. Projects + Orders~ 9...11 Mio. in total

e 1 5Permoserstra04303Leipzig;Germany

Tel:+49 341 235 2308Fax:+49 341 235 2313e-mail:[email protected]: -

http://www.iomleipzig.de

Board of Directors:Prof.Dr.B. RauschenbachNN



Chemical Department

Physical Department

~ 50 %Scientists

bersichtOutline

News on Ion Beam Figuring - IBFOther ion beam surface processing techniquesAtmospheric Plasma Jet Machining - PJM

3Leibniz-InstitutfrOberflchenmodifizierung

ManufacturingTechnologies to Support Large Science ProjectsParis, France 25th - 26th November 2010

iE x p e r t i s e o f I O M i i n l - i

ultra-precision surface processing

...applied to optics

> Ion Beam Figuring>IonBeam

Planarization

> Ion Beam Smoothing> Ion Beam Patterning

> Ion Beam ProportionalTransfer

IOMs R&D activities inIon Beam and Plasma Jet Surface Processingmore than 35 years experience in (R)IBE - PT since 1986 in IBF for optics fabricationSince 1993 in PACE and PJM for optics fabrication



> Ion BeamAssisted Deposition

> Low EnergyIon Implantation

> Plasma Jet CNCmachining etching anddeposition

OpticIon Source

PlasmaSource

Optic

4

Expertise of IOM in ultra-precision surface processing

> Basic Research and Development of: -Processing

- Software

- Components- Systems

References:

... and others

5

Effective wavelength range

Spatial wavelength size of surface features [m]

10-110-210-310-410-510-610-710-8

Ion beam and Plasma jetdeterministic figuring

?

Ion beamnano structuring/

smoothing

Surface topology Mid Spatial Frequency Roughness -MSFR HighSpatialFrequencyRoughnessHSFRm

100mm 160m 1m

Optical / tactileprofilerInterferometry

Leibniz-Institutfr Oberflchenmodifizierung

White light andMicro-interferometer


AFMSEM

6

Space Optics ion beam finished by IOMSOFIA Secondary mirror IBF in IOM 2001: 352 mm SiC, 39 nm rms



Ion beam-figuring of synchrotron-optics

Plano-Elliptical Focusing Mirror250

> 40 mm Kaufman-Source> Hot Filament-Neutralisation> 800 V / 20mA

100

50

0

200

Profi

lhohe

mnrn/

150

Ausgangsflche1.Bearbeitung3.Bearbeitung2.Bearbeitung

0 50 100 150 200

mm

42m

SR beam spotsand horizontalIntensity profiles

SR Spot size(FWHM)

17mSurface status

RMS(arcsec]

PV(arcsec]

RMS(nm]

PV(nm]

FWHM(mm]

initial state 1.49 5.02 47.3 191.1

1 st run 0.44 2.43 13.3 58.1 4

2 nd run

3 rd run (finalstate)

0.26 1.51 2.9 14.3 4

0.1380138 0.85 1.4 8.8 2

1,49 arcsecbefore



110100908070605040302010

Synchrotron beam line grating by large area uniform dwell time etching

X-ray grating specification

Pitch = pDuty cycle = t/pEtching depth =h

pt

Si-Si-subsratesubstrate

h

190mm

Parameter type 1 type 5Substrate size 90mm x 30mm - 40mm thick 200mm x 30mm - 30mm thickLine Density 700 l/mm 700 l/mm 1400 mm-1 1400 mm-1

track 1 track 2 track 1 track 2Energy range 10 - 20 eV 15 - 25 eV 150-400 eV 600-1600 eVGroove depth 10% 900 A 800 A 130 to 140 A 55 to 60 ADuty cycle (groove/period) 0.55 0.55 0.55 to 0.6 0.55Useful area 80 x 10mm2 80 x 10mm2 110 10 mm2 190 10 mm2



New ideas for improving ion beam figuring performances

Disadvantages of standard dwell time ion beam figuring usingcw ion beam:

1. Fixed beam size constrains effectivefiguring to spatial wavelength equal orlarger then about the beam size,

1. CW ion beam current regime togetherwith the maximum motion velocityand upper limits of the dynamics

(accell. + decell.) of the mechanicalmotion system cause inefficiency withrespect to local depth resolution (steep

surface gradients) and the waste materialremoval at the zero surface errorposition,

1. Only sequential processing of surfacesby raster scan and no parallel processing.



Ion source technology = key for UPSPBase source: 40 mm RF Source, Hidden Hot Filament Neutralisation

100mm

2mm 1mm 0.5mm

Working distance [mm]: 55 15 10 6

Removal spotFWHM [mm]: 8 2.1 1.10.6



Motion ControlAxes-controller,-amplifier(Aerotech)

New!IBF using motion synchronized PWM ion beam control

Initial and FinalSurface Data tmech , tpwm

CNanotec

Parameter

DtCalc

CAM-Table

Beam Profile Data

Beam on /off

PWM (EIA485) Uacc

Beam switching-Parameters:f = 10 kHz;

tpuls = 2 ... 98 s-* PWM = 2 ... 98%

3-(5-)Axes-

Beam switching unit

UbeamIon source


PC I/O: Firewire


3-(5-)Axes-Motion System

12

Improved ion beam figuring using PWM of a RF-ion sourceParametersofaxis-system:

Max. axis velocity vmax : 40 mm/sMin.dwell time tmin : 2 ms5 nmRange for PWM = 2...98%

Max.accelerationamax :0.5 m/s2Assumed time for5 nmacceleration ta: 2 ms

Ar ion beam:hRemoval rate r: 2 nm/sFWHM:1.5mmhVolume removal rate: 3,06*10-4mm3/min

Results:Principlevmaxv* max= >90vmax

I = f(TV) Base removal dwell time+PWM: 0,02 IEIR-19Dcessing time-dwell timPtiM:= 10% 50% 90% 3:46 Processing time dwell time+PWM: 2:25

IBF-Simulation for dwell time scanning + synchronized PWM[nm][nm]InitialAfter IBF

StandardIBF+ PWM

4 Reduction of the Base removal to 2 %4 Reduction of the Processing time to 64%

5V:motion synchronized, PiAlivisbeam control enables:

At = 100s=const. Base removal dwell time: 1,27

I = const

Standard IBF

Local distribution of the PWM- dwell timesLocal distribution of the mechanical dwell times

Leibniz-InstitutManufacturingTechnologiestoSupportLargeScienceProjectsfr OberflchenmodifizierungParis,France25th-26thNovember2010

minimal material removal[ms]

in certain cases strong reduction of the processing time low acceleration /deceleration precision figuring of partial areas of the surface

of the axes system

[ms]

Effective dwell time distribution

13

New! Segmented grid linear ion source with PWL controlled ion beam

PWM = 0.02 ... 0.98 %tpulse= 0.05 ... 0.2 msf = 0.5 ... 20 kHz

Scholze et al. Rev.Sci.Instrum.77, 03C107 (2006)





Ion beam profile shaping of a linear ion source by PWM

400 600 800 1000 1200 1400 1600

1/m

A

600

400

200

800

0

'Beam'Accj

2,8

2,6

2,4

2,2

2,0

1,8

1,6

1,4

mA/cm

2

UBeam / V

Total ion current 'Beam, ion current density at the maximum of the beam crosssection jand the ion current measured on the accelerator grid 'Acc in dependence of thebeam votage UBeam of the linear ion source.

Different beam profiles along the segmented ion source axis by PWMof every segment measure by a Faraday-cupline arraywith30 cups,distance200mm.

1.000.750.500.25

0.000200 400 600Length[mm]

1.20.90.60.3

0.00200 400 600

Length [mm]

0.600.450.300.15

0.000200 400 600Length [mm]

Ion

curr

ent

dens

ity[m

A/cm

2 ]

15

Modular2.45Ghzdrivenionsourcewithsegmentedgridsystemfor ion beam PWM control of each single gridsegment.

Efficient IBF of systematic surface shape distortions

Y [mm] (distance from the edge of the lens)

Optimizedparameterof linear ionbeamsource(e.g. length 1m):

Ion source position: parallel to the edge of an optic withsystematic edge contour error

Systematic edge error = 3.6 m PVIon beam FWHM = 9.9 -11.9 mmRemoval rate at 1 mAcm-2 = 1 nm/s (=3.6 m/h)Resulting etching time 1hResidual error (rms) = 250 nm

X [mm] (parallel to the edge)

Part of the systematic edge figure error

- In situ PWM ion beam shaping of a linearsegmented grid ion source enables:

- efficient surface figuring of large optics esp. forsystematic surface errors

- after continuing development probably efficientfiguring arbitary shaped surfaces

mean edge cross sectionoptimized gassian ion beam profileresidual error of the edge cross section

2500

2000

1500

1000

500

0

profile

heigh

t[nm]

0 5 10 15 20

A

Simulation study

[nm]4500

4000

3500

3000

2500

profi

leheig

ht[nm

]2000

-60 -40 -20B 0 20 40 60

4500

4000

3500

3000

2500

2000

1500

1000

500

0

edge error profile parallel to the edge



Ion beam smoothing of ion beam etched ZerodurMulti step process with Si coating step (patented by Schott)

Zerodur surface after IBFcoated with Si thin filmafter smoothing

10-410-310-210-1

105

Rq = 0.142 0.007 nm3nm

0nm

10-1

250nm

104

103

102

101

pow

ersp

ectra

lden

sity

PSD

[nli

100

-1]spatial frequency f [nm


Leibniz-Institutfr Oberflchenmodifizierung

Ion beam smoothing of a SiC surfaceIon beam direct smoothing - IBS Ion beam planarization - IBP(a): Rq = 2.15 nm

(c): Rq = 0.54 nm

750 nm

750 nm

(b): Rq = 0.81 nm

750 nm

8 nm

0 nm

(a): Rq = 4.16 nm

2000 nm 2000 nm

(b): Rq = 0.88 nm10 nm

0 nm

106

1st step: photo resist layer 5080nm spray coating105

2ndstep Ark, 700eV, 200mAcm-2, iia 30

10-110-310-210-1

104

103

102

PSD

[nm

4]

101

100

(d)

SiC as polishedIBS step#1IBS step#2

spatial frequency f [nm-1]

Ark, Eion =800eV, jion =250 mAcm2, simultaneous sample rotation, a) beforeIBS, b) 1st step iia 70, c) 2nd step iia 0

Leibniz-InstitutManufacturing Technologies to Support Large Science ProjectsfrOberflchenmodifizierungParis, France 25th - 26th November 2010

18

Nano optics made by nature... and ... by ion beamInP-surfacestructure after ion beam bombardment

500 nm500 m

Faceteye of a moth

10 m

Facets

1 m

Structuredfacet surface



Self-assembling nanostructures by ion beam bombardment

Eion = 2000 eV, Xe+ Si

500 nm

ion = 25 ion = 26

Ion beam direction

F. Frost, ... Appl. Phys. Lett. 92, 063102 (2008); Appl. Phys. Lett. 88, 173115 (2006)





Anti reflecting surface by self assembling nano-structures

IBE-nano structureson GaSb surface,Au-coated

Reflectivity Measurement: Dr. M. Schubert, Uni Leipzig

Ar+-Ion Beam(500 eV)

GaSb

z=100nm

1000nm 125nm

Refle

ctivit

y[%]

100

40

20

80

60

200 300 400 500 600 700 800 900 1000

GaSb IBE nano structured + AuGaSbpolished + Au

Wavelength [nm]

polished

~ 5 cm

nano-structured

Precision Atmospheric Plasma Jet Machining (PJM)



Introduction - Plasma Jet Machining (PJM)PJM a fast and highly efficient technology for surface figuring(100-1000 faster than ion beam figuring)

Reactive plasma jet etching / deposition / surface modification Deep asphere fabrication, figure error correction Process in ambient air, normal pressure No mechanical forces applied to surface Sub-surface damage free Capability of sub-surface damage removal

Lithography Telescopes Space Optics Synchrotron Radiation



Plasma Jet Machining (PJM) - PrincipleCentral gas inlet

(e.g. Ar + CF4 )

-Chemical reaction onsurface:

Si + 4F SiF4

Plasma jet source

Plasma jet

Lens

Chemical material removal Gaussian jet tool function Process in normal environment (air) No vacuum

Materials: silicon, fused silica, SiC,ULE, (Zerodur)

G. Boehm, W. Frank, A. Schindler, et al. , Plasma jet chemical etching - a tool for the figuring of optical precision aspheres, PrecisionScience and Technology for Perfect Surfaces, eds. Y.Furukawa, Y. Mori & T. Kataoka , The Japan Society for Precision Engineering, Tokyo(1999) 231-236 (Proc. of the 9th ICPE, Osaka/Japan, 29.08.-01.09.1999)



Shieldgas (e.g.N2)

Grounded shieldHF

Pipe electrode

Extended shield

Plasma jet(ions + electrons + neutrals)

Radical jet(e.g.Atomic fluorine F)

F

Substrate

2.45 GHz Plasma jet sources of IOM

High-power source Compact source Mini source

Mass ca. [kg]: 15 2 0.1

Power max [W] :

PJM - high rate removal on workpiece edges

Simulation studyProblem: reduced removal on workpiece edges at mechanical sub-aperture techniques

X[mm]

Sim strategy: Approximation of edge cross section profile by discrete Gaussian grooves

Parameters: Horizontal position of groove, scan velocity

Constraints: Velocity (temperature) dependent FWHM and removal rate

Plasma jet edge machining

Heigh

t[pm

]

2.5

0.5

1.5

2

00 2 4 6 8 10 12 14 16

1

Typical edge cross section



PJM - high rate removal on workpiece edgesResults

Velocity [mm/s] Grooveposition[mm]

6.5049 -1.000

9.2770 0.9020

7.9587 2.6521

8.8137 4.9964

12.1257 7.4343

19.3919 9.9505

X [mm]

00

0-0 Re

sidua

lerro

r[pm

]I

-_

--

He

ig

ht

[p

m]

-0.02

-0.030 2 4 6 8 10 12 14 16

2.5

0.5

.03

.02

.01

.01

1.5

2

00 2 4 6 8 10 12 14 16

0

1

Theoretical residual error

RMS: 0.009 m

X [mm]

edge profile

grooves

Assumed material: fused silica

- Volume removal rate: 2.5 mm3/min

- Effective correction rate: 1.6 mm/s- Plasma jet machining is a potential technology

for effective treatment of edges

32Leibniz-Institut Manufacturing Technologies to Support Large Science ProjectsfrOberflchenmodifizierungParis, France 25th - 26th November 2010

Nanometer PJM shape correction with sub-mm spatial resolution

Fused Silica Concave Asphere, 134 mm

Processing Parameter: Plasmajet Gaussian fit FWHM 0.67 mm Removal Rate 0.0014 mm3/min Pixel size 146 m Average Scan Velocity 6 mm/s Overall Machining time 4h 10 min

Base Removal 8.1 nm 5-Axes-CNC-Plasma-Jet-Figuring

35 nm 35 nm

0nm 0 nm

Before PJMRMS 2.81 nm, PV 32.77nm

After PJM CorrectionRMS 1.20 nm, PV 17.71 nm



Summary - PJM

PJM is very efficient for deterministic surface shaping with nanometric

accuracy andhigh spatial resolution

PJM works at atmospheric pressure

PJM requires less polishing afterwards because no SSD occur

PJM covers a wide range of applications like- Fabrication of aspheres and free forms with lateral dimensions from 5 to 500 mm and machining

depths up to some millimeters

- Reduction of figure and/or mid spatial errors (> 0.5 mm) -Damage layer removal and surface preparation

PJM works currently on Fused Silica, ULE, Silicon, Silicon Carbide, and Zerodur



AcknowledgementsT. Hnsel, A. Nickel, F. Frost, R. Fechner, G. Bhm, H. Paetzelt, F. Pietag, D. Flamm, D. Hirsch, H. Neumann, I. Herold, H.Beck, P. Hertel, G. Gleisberg, E. Salamatin, K. Ohndorf, A. Mill, T. Freyer, H. Bucsi, S. Daum, P. Seidel, M. Eichentopf,H. Neumann, F. Scholze, S. Mieler, J. Meister

Thanks for Collaboration

IBF and PJM device and equipmentdevelopment and manufacturing

Financial support by:

Project-No.:13N16011 and 13 N 7016/0 and

+ Project-No.: 5950/914

Young Researchers Group:Ultra precision manufacturing usingatomic particle beams

contractsFOR 365/1-1/2;SCHI 434/11-1

is gratefully acknowledged.Leibniz-Institut Manufacturing Technologies to Support Large Science ProjectsfrOberflchenmodifizierungParis, France 25th - 26th November 2010 35

Thank You !Major Equipment for Ion Beam Figuring and Plasma Jet Machining at IOM

5-Axes Ion BeamFiguring Machine

ISARA400TactileCMMavailable 2011

Aspheric StitchingInterferometer (ASI)

5-AxesAtmosphericPJMFiguring Machine

Ion Source Machine1-Axis 60 cm Linear Variable Beam

Diameter RF Ion source



Surface Engineering PJM1

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