coherence scanning interferometry

4/4/2013

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Suresh K. Ramasamy PhDApril 2013

COHERENCE SCANNING INTERFEROMETRY

Part 2. Quantification of errors

SKR CSI 2 ASME TUTORIALS 2012

Z based errors

XY based errors

Part based errors

Summary Table

OUTLINE

“Sometimes I lie awake at night and ask, “Where have I gone wrong?” then a voice says to me, “This is going to make more then one night”

‐ Charles M. Schulz

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SUMMARY TABLE


Dr. Jayaraman Raja

Dr. Brian Boudreau

CSI support: Bala Muralikrishnan (NIST)

Claudiu Guisca (NPL)

Don Cohen (Michigan Metrology)

Jimmie Miller (UNCC)

Manas Lakshmipathy (Zygo)

Peter de Groot (Zygo)

ACKNOWLEDGEMENTS

Sample support:Chris Wichern (Nanofocus)

Laura Shaw (University Erlangen‐Nuremberg)

Rose Peet (RPC Photonics)

Tatsuya Sugihara (Osaka University)

Email id: [email protected]

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QUESTIONS ?

"Things should be made as simple as possible, but no simpler." ‐ Albert Einstein


Z BASED ERRORS

Sequential height repeatability

Scan length (for systems with no reference signal)

Z stage non‐ l inearity

NA correction

Algorithm – peak and phase detection, noise reduction / interpolation

Focus location

Environment changes

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XY BASED ERRORS

Camera non‐ l inear warping error

Sequential repeatability for dimensional measurement

Stage reproducibility/ non‐ l inearity

Stitch errors

Objective and turret repositioning errors


PART BASED ERRORS

Dissimilar materials

Shape of part

AW of parts ‐ ITF

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Z SEQUENTIAL MEASUREMENT REPEATABILITY

Reference Flat Standard

10 sequential measurements

Average – individual data

Average of RMS

0.33 nm


SCAN LENGTH

Step Height Standard

5 scan lengths

All magnifications

100 µm scan is taken as basis

Obj. 50xZoom 0.5x Zoom 1.0x Zoom 2.0x Zoom 0.5x Zoom 1.0x Zoom 2.0x Zoom 0.5x

5 1.811 1.813 1.809 1.813 1.816 1.815 1.81610 1.813 1.812 1.810 1.814 1.816 1.815 1.81720 1.813 1.813 1.812 1.814 1.816 1.814 1.81540 1.811 1.811 1.810 1.814 1.815 1.814 1.81565 1.810 1.810 1.807 1.813 1.814 1.814 1.815

100 1.809 1.809 1.807 1.812 1.813 1.813 1.813150 1.810 1.809 1.806 1.811 1.811 1.811 1.812

5 - - - - - - -10 - - - - - - -20 - - - - - - -40 - - - - - - -65 23.925 23.922 23.937 23.926 23.929 23.927 23.925

100 23.915 23.905 23.922 23.915 23.915 23.913 23.914150 23.907 23.895 23.917 23.907 23.904 23.902 23.904

5 - - - - - - -10 - - - - - - -20 - - - - - - -40 - - - - - - -65 - - - - - - -

100 49.006 49.007 48.989 48.977 48.967 48.966 48.897150 48.995 48.998 48.975 48.963 48.953 48.952 48.886

5 1.0011 1.0021 1.0011 1.0006 1.0015 1.0014 1.001410 1.0019 1.0013 1.0014 1.0010 1.0018 1.0012 1.001920 1.0022 1.0021 1.0025 1.0009 1.0019 1.0008 1.001140 1.0012 1.0008 1.0015 1.0009 1.0010 1.0006 1.001265 1.0005 1.0006 1.0004 1.0005 1.0007 1.0005 1.0008

100 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000150 1.0000 0.9996 0.9996 0.9995 0.9995 0.9994 0.9996

Ste

p H

t 23

.847

µm

Ste

p H

t 49

.094

µm

Rat

io w

rt 1

00µ

m

scan

Scan Length

Obj 2.5x Obj 10x

Ste

p H

t 1.

816µ

m

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Z STAGE NON‐LINEARITY

Reference Flat Standard

Tit led along X axis to cover entire range

(a) Average of 10 msmts. to reduce noise

Z lowered by one fr inge

(b) Average of 10 msmts.

RMS of a ‐b

Z raised by 2 fr inges

(c) Average of 10 msmts.

RMS of a ‐c

Repeat with standard t i l ted in opposite direct ion in X axis

Repeat the same along Y axis

Average of 8 RMS


NA CORRECTION


20 msmts. taken

10x mag is taken as basis

Obj. 50xZoom 1x Zoom 2x Zoom 0.5x Zoom 1x Zoom 2x Zoom 0.5x

1 48.9593 48.9593 48.9624 48.9601 48.9602 48.96182 48.9649 48.9608 48.9635 48.9546 48.9600 48.96213 48.9643 48.9639 48.9612 48.9541 48.9673 48.96264 48.9639 48.9620 48.9667 48.9529 48.9569 48.97105 48.9591 48.9614 48.9639 48.9528 48.9641 48.96936 48.9596 48.9643 48.9634 48.9587 48.9612 48.96677 48.9637 48.9652 48.9627 48.9537 48.9642 48.96118 48.9617 48.9669 48.9630 48.9565 48.9630 48.96609 48.9560 48.9578 48.9658 48.9532 48.9667 48.968410 48.9589 48.9578 48.9714 48.9522 48.9623 48.964611 48.9598 48.9653 48.9653 48.9590 48.9625 48.963512 48.9577 48.9571 48.9662 48.9581 48.9618 48.961813 48.9668 48.9617 48.9614 48.9569 48.9614 48.966614 48.9621 48.9685 48.9620 48.9552 48.9582 48.959315 48.9587 48.9693 48.9673 48.9536 48.9632 48.964816 48.9590 48.9670 48.9666 48.9532 48.9633 48.968617 48.9662 48.9649 48.9664 48.9549 48.9634 48.965418 48.9627 48.9620 48.9687 48.9566 48.9646 48.960419 48.9634 48.9648 48.9659 48.9512 48.9608 48.963820 48.9617 48.9691 48.9645 48.9597 48.9676 48.9655

average 48.9615 48.9635 48.9649 48.9554 48.9626 48.9647std. dev 0.0030 0.0038 0.0026 0.0027 0.0028 0.0032

NAC 1.0001 1.0002 1.0002 1.0000 1.0001 1.0002

Run No.Obj. 2.5x Obj. 10x

Average Step Height in µm

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Normal resolution mode

ALGORITHM INDUCED 1/2

High resolution modeHigh2G resolution mode


ALGORITHM INDUCED 2/2

Edge Transition errors on square wave artifact

-0.12

-0.07

-0.02

0.03

0.08

0.1 0.15 0.2 0.25 0.3

Distance in mm

He

igh

t in

µm

Mode 1 Mode 2 Mode 3

Surface Profile of 150nm Random Surface under different FDA Resolution Modes

-1.5

-1

-0.5

0

0.5

1

1.5

2

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97Z H

eig

ht in

µm

Mode 1 Mode 2 Mode 3

0102030405060708090

100110120130140150160170180190200210220230

Mode 1 Mode 2 Mode 3 Mode 1 Mode 2 Mode 3 Mode 1 Mode 2 Mode 3

30 nm random surface 100 nm random surface 150 nm random surface

Measu

red

Ra v

alu

es in

nm

0

10

20

30

40

50

60

70

80

90

30 nmrandomsurface

40 nm heightsquarewave

60 nmsinusoidsurface

100 nmrandomsurface

150 nmrandomsurface

1000 nmsinusoid surface

De

via

tio

n b

etw

ee

n a

lgo

rith

ms

in n

m

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FOCUS VARIATION


first msmt. with bottom surface in focus

Second msmt. at +25µm above

Critical for cylindrical surface msmts.


ENVIRONMENTAL IMPACTS

Square wave Standard

Combination of XY and Z in one test

Height 1 sigma = 0.002µm, Width 1 sigma = 0.048µm

24.258

24.260

24.262

24.264

24.266

24.268

24.270

24.272

24.274

24.276

24.278

17:5

8:25

18:2

8:52

18:5

9:20

19:2

9:47

20:0

0:14

20:3

0:42

21:0

1:09

21:3

1:36

22:0

2:04

22:3

2:31

23:0

2:58

23:3

3:26

0:03

:53

0:34

:21

1:04

:48

1:35

:15

2:05

:43

2:36

:10

3:06

:38

3:37

:05

4:07

:33

4:38

:00

5:08

:28

5:38

:55

6:09

:22

Time in hr:min:sec

Ste

p H

eight in

µm

51.600

51.650

51.700

51.750

51.800

51.850

51.900

51.950

52.000

Ste

p W

idth

in µ

m

step ht step width

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CAMERA NON‐LINEAR WARP

-100

-80

-60

-40

-20

0

20

40

60

80

100

-120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120

-100

-80

-60

-40

-20

0

20

40

60

80

100

-120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120


XY SEQUENTIAL REPEATABILITY

Standard Deviation in µm of 25 measurementsStandard [0.25µm (dia.), 0.13µm (center)] Autofocus [0.25µm (dia.), 0.19µm (center)]

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

Dia. CX CY Dia. CX CY Dia. CX CY Dia. CX CY Dia. CX CY Dia. CX CY

A B C D E F

Std

. Dev

in µ

m

Without Autofocus With Autofocus

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XY REPRODUCIBILITY

1

52

3

4

7

8

9 11

12

6

10

Range Value over multiple runs

0

1

2

3

4

5

6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Runs

Ra

ng

e in

µm


STITCHING ERRORS

ISO Flatness (nm) (Average difference 8 nm)

4

6

8

10

12

14

16

18

2-1

3-2

4-3

5-4

6-5

7-6

8-7

9-8

10

-9

11-1

0

12-1

1

13-1

2

14-1

3

15-1

4

16-1

5

17-1

6

18-1

7

19-1

8

20-1

9

21-2

0

22-2

1

23-2

2

24-2

3

25-2

4

26-2

5

Run Delta

ISO

Fla

tne

ss

(nm

)

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TURRET REPOSITIONING ERROR


DISSIMILAR MATERIALS

A B A

coherence scanning interferometry

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