magnetron sputtering of metal oxides - vacuum … optics.pdf · plasma assisted reactive magnetron...

Plasma Assisted Reactive Magnetron Sputtering of High Performance Interference Filters

A. Zöller, H. Hagedorn, W. Lehnert, J. Pistner, M. Scherer,

Alzenau

2Photonex 2012; Plasma Assisted Reactive Magnetron Sputtering of High Performance Interference Filters

Outline

� Plasma Assisted Reactive Magnetron Sputtering (PARMS)

� System layout

� Material properties

� Typical interference filter application

� UV coatings

� Defect investigation

� LIDT on HR mirrors

� Conclusion


Plasma Assisted Reactive Magnetron Sputtering

Load lock valve

Dual magnetronProcess module

Turn table

Substrate heater

Plasma source

Substrate



Ar+e-

Magnetron 1

MF Power supply ~

Magnetron 2

Cathode

AnodeAnode

Cathode

Magnetron 2 Magnetron 1

Vt

Plasma stabilization by MF Dual Magnetron Sputtering


System layout

� HELIOS 400 / 800

• 100mm

- 16 substrate carrier

- useful area 12 x 78cm²

= 0,12m²

• 200mm- 12 substrate carrier

- useful area 12 x 314cm²

= 0,38m²


Substrate handling

HELIOS single substrate load lock


Substrate handling

HELIOS substrate transfer


Direct optical monitoring

■ Intermittent direct on-substrate monitoring

Load Lock Valve


Coating materials

�� Low intrinsic compressive coating stress

0,33- 1001,48SiO2

0,5-1802,075HfO2

0,5-702,13ZrO2

0,6- 902,166Ta2O5

0,55- 1502,365Nb2O5

0,4- 1151,67Al2O3

0,45- 3001,48SiO2

Deposition rate[nm/s]

Film stress [MPa]

Ref. index n@ 550nm

Material



Helios magnetron sputtering system with direct monitoring

Coating materials: Nb2O5 / SiO2

Short wave pass filter

OD > 7 @ 750nm-1100nm



0

10

20

30

40

50

60

70

80

90

100

200 300 400 500 600 700 800 900 1000 1100 1200

Wavelength (nm)

Tra

ns

mit

tan

ce

(%

)

Theory_Front+Back

090609-2-4-F+B_P2

090609-2-4-F+B_P3

090609-2-4-F+B_P4

090615-B+F_P9

090615-B+F_P11

� Band pass filter with broad blocking range OD6

Design

Front and backside

coating

H = Nb2O5

L = SiO2

Total layer number

94 / 104

Total thickness

9,4µm / 10.4µm



11-Cavity Bandpass Filter Ta (50% BW=30nm)


Optical Performance of the monitor glass (first run)

(w/o backside AR coating)Coating materials: Ta2O5 / SiO2

0

10

20

30

40

50

60

70

80

90

100

410 430 450 470 490 510

Wavelength (nm)

Tra

nsm

itta

nce

(%

)

Theory

OMS in chamber



13-Cavity Bandpass Filter for life science applications


0,5 dB (89%) BW– 47,7 nm

3dB (50%) BW – 48,0 nm

10dB (10%) BW – 49,2 nm

30dB (0,1%) BW – 53 nm

steepness – >50dB/nm

Highest peak - 0,3dB (95%)w/o backside AR

-40

-35

-30

-25

-20

-15

-10

-5

0

400 420 440 460 480 500 520 540

Wavelength (nm)

Tra

ns

mit

an

ce

(d

B)

1st run

2nd run

Coating materials: Nb2O5 / SiO2

Optical Performance of the monitor glass (w/o backside AR coating)



1-Cavity NBP Filter with Ta2O5/SiO2

Magnetron sputtering with direct monitoring

Optical Performance of the monitor glass (w/o backside AR-coating)

Highest peak – 0,2 dB

3dB (50%) BW – 2,1 nm

Substrates 16

Useful area @ Uniformity <+-0,2%

Diameter 60- 80mm

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1050 1052 1054 1056 1058 1060 1062 1064 1066 1068 1070 1072 1074 1076 1078 1080

Wavelength / nm

Tra

nsm

itta

nce

/ d

B

Absorption:

Single Layer 4 λλλλ /4@1064nm

Ta2O5 < 4ppmSiO2 < 3ppm



Single side coating

H = Nb2O5

L = SiO2

Total layer number

198

Total thickness

20µm

Batch time

app. 13h

4-fold-notch filter, AOI=10°

0

10

20

30

40

50

60

70

80

90

100

420 460 500 540 580 620 660 700 740

Wavelength [nm]

Tra

nsm

itta

nce [

%]

Theory

Pos 3

Pos 4

Pos 5

Pos 7

Pos 9

Pos 10

Pos 11

Spec. Tavg

� Multi notch filter


UV- and VIS Filter Coatings by PARMS

Dispersion n & k of optimized HfO2, ZrO2, and Ta2O5

2

2.05

2.1

2.15

2.2

2.25

2.3

2.35

2.4

2.45

2.5

200 250 300 350 400 450 500 550 600

Wavelength (nm)

Refr

acti

ve I

nd

ex n

0.0E+00

1.0E-04

2.0E-04

3.0E-04

4.0E-04

5.0E-04

6.0E-04

7.0E-04

8.0E-04

9.0E-04

1.0E-03

Exti

ncti

on

k

n Ta2O5 n ZrO2 n HfO2

k Ta2O5 k ZrO2 k HfO2


UV- and VIS Filter Coatings by PARMS

0,5-170λ λ λ λ ≥ 2502,075HfO2

0,5-70λ λ λ λ ≥ 2802,130ZrO2

0,6-90λ λ λ λ ≥ 3252,166Ta2O5

Rate (nm/s)Streß (MPa)k < 1 E- 3n (550nm)Material

Properties of optimized HfO2, ZrO2, and Ta2O5 films


UV- Filter Coatings by PARMS

Al2O3 and SiO2 for UV applications

� Dispersion n & k of optimized Al2O3 and SiO2

1,50

1,55

1,60

1,65

1,70

1,75

1,80

1,85

1,90

200 210 220 230 240 250 260 270 280

Wavelength [nm]

Refr

acti

ve I

nd

ex

n

0,0E+00

5,0E-04

1,0E-03

1,5E-03

2,0E-03

2,5E-03

3,0E-03

3,5E-03

4,0E-03

Exti

ncti

on

k

n SiO2 n Al2O3 k SiO2 k Al2O3


UV Filter Coatings by PARMS

Direct optical monitoring @212nm

- BP Filter 212nm, 6 cavity, 90 layer Al2O3 and SiO2

0

10

20

30

40

50

60

70

80

90

100

200 205 210 215 220 225

Wavelength (nm)

Tra

ns

mit

tan

ce

(%

)

measured in chamber

CWL=212.025

FWHM=7.55nm


UV- Filter Coatings by PARMS

Al2O3 for UV applications

� Mirror for 193nm, Result

Mirror for 193nm based on Al2O3 and SiO2 with HELIOS PARMS

0

2

4

6

8

10

12

14

16

18

20

185 190 195 200 205

Wavelength [nm]

Tra

nsm

itta

nce

[%

]

80

82

84

86

88

90

92

94

96

98

100

Refl

ec

tan

ce [

%]

T Helios R Helios R APS


■ Refractive index n at 550nm vs. power ratio Nb/Si+Nb

Co-sputtering: Intermediate refractive indices

Refractive index vs. power ratio of reactive co-sputtered NbxSiyOz layers

1,4

1,5

1,6

1,7

1,8

1,9

2

2,1

2,2

2,3

2,4

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

Power ratio [Nb/Si+Nb]

Re

frac

tiv

e i

nd

ex

n

n at 550nm

SiO2 Nb2O5


Rugate type Filter with co-sputtering

■ Rugate/notch filter design: λλλλ/4 design

Refractive index profile

1,4

1,5

1,6

1,7

1,8

1,9

2,0

2,1

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41

Number of QWOT

Re

fra

cti

ve

in

de

x a

t 6

00

nm


■ Rugate filter with λλλλ/4 layer design

- Comparison with theory and reproducibility

Rugate type Filter with co-sputtering

HELIOS rugate/notch Filter, comparison of theory with 4 repro runs

0

10

20

30

40

50

60

70

80

90

100

350 400 450 500 550 600 650 700 750 800 850

Wavelength [nm]

Tra

ns

mit

tan

ce [

%] 050607-02 Pos. 2

050607-05 Pos. 2

050608-02 Pos. 2

050608-05 Pos. 2

Rugate Disign-41L

Process time 3h


Defect formation Helios prototype, SiO2

� Defect density of < 5 cm-2 for a longer period achievable

� No onset of defect generation until the end of the target lifetime

� Advanced configuration: Circular SiO2 target, RF-powered


LIDT S-on-1 @ 1064nm SiO2 (RF)

� Single layer 4 L

� Substrate Suprasil


LIDT S-on-1 @ 1064nm SiO2 (RF); Ta2O5(MF)

� HR Mirror (HL)^11 L

� Substrate Suprasil




� Substrate Silicon Wafer


PARMS Coatings @ 1064nm SiO2/Ta2O5

99.991%

90ppm

0.47nm

Reflection

Total loss

(CRD)

Surface roughness

RMS

158 J/cm2

0%- LIDT

@ 1064nm

H 1 on 1

SiO2/Ta2O5

Si-Wafer

/super polished

Coating material

Substrate

HR Mirror

HL^18L

@1064nm

Design


Conclusion

� PARMS has shown within the last 10 years to be

capable to produce the most complex interference filter

with high productivity

� PARMS can produce coatings with high laser damage

threshold and very low total losses

� Using RF sputtering for SiO2 can lower the defect

density significant


Thank you for your attention !

magnetron sputtering of metal oxides - vacuum … optics.pdf · plasma assisted reactive magnetron...

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