12011 NCSL International Workshop and Symposium

Prospects of multi-sensor technology for large-area applications in micro- and nanometrology

E. Manske1, G. Jäger1, T. Hausotte2

1Ilmenau University of Technology, 2University Erlangen-Nuremberg

2011 NCSL International Workshop and Symposium08/21/2011 - 08/25/2011, National Harbor

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Outline

1. Motivation

2. Nanopositioning and Nanomeasuring Machine

3. Multi-Sensor Approach

4. Conclusion and Outlook

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Motivation

Micro- and nanotechnology, micro-systems technology, precision optical manufacturing, micro-processing technology

Combination of Nanopositioning and Nanomeasuring Machines

with Multi-Sensor Technology

“Metrology methods must routinely measure near and at atomic scale dimensions” ITRS 2009

• Structures reach atomic dimensions (ITRS)• Structures are becoming more complex • Increasingly larger surface regions• Higher aspect ratios • Increasing requirements for real 3D-measuring tasks

Existing measurement approaches not sufficient

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Nanopositioning and Nanomeasuring Maschine

length and angular measuring systems

nanoprobe

specimen

measuring table(mirror corner)

measuring frame

Signal processing, control, operator system

• Abbe error free measurement in all measuring axes • permanent compensation of all guiding errors • nanoprobes act as zero indicators

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3-D-Abbe-Comparator-Principle

0ioffl

0i

and

0sin ioffi ill

zyxi ,,Extended approach:

with

Ernst Abbe(1840-1905)

The measuring standard and the object to be measured have to be in line. 0offl

“The measuring apparatus is to be arranged in such a way that the distance to be measured is a straight-line extension of the graduation used as a scale”.

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NPM-Machine Approach with Laser Focus Sensor

Metrology frame

x,y,z-stage of the NPM-Machine

(Zero point indicator)

sample

x,y,z-stage of the NPNM-Machine

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Autocollimator for active angular control

Measuring range: 50 arcsec x 50 arcsec

Resolution: 8.10-4 arcsec

Angular deviation of the NPM-machine: < 0.05 arcsec

• automatic control of pitch and yaw angle• measurement of roll angle

Optical fiber

Position sensitivediode

Beam splitterAchromat

Measuring mirror

Bending mirror

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Nanopositioning and Nanomeasuring Maschine

• Large measuring range (referred to atomic force microscopy):

25 mm x 25 mm x 5 mm

• Subnanometre resolution: 0.08 nm

• Nanometre reproducibilityand uncertainty

• Universal applicability ofseveral optical, tactile andAFM probes

NPM-Machine

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Basic components of the Nanomeasuring Machine

Metrology frame(Zerodur)

3D-Stage

Corner mirror

X-interferometerY-interferometer

Abbepoint

Angular sensor Angular sensor

measuring range: 25 x 25 x 5 mm3, resolution: 0.1 nm

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Positioning steps of 1 nm in all axes

17resolution: 0.1 nm

z-axis

y-axis

x-axis

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Measurement Stability of the NPM-Machine

Länge [nm]

2

time/ s

310,5 1,5 2,5 3,5

3

2

4

1

0

z=0,23 nm

y=0,27 nm

x=0,29 nm

3

2

4

1

0

2 310,5 1,5 2,5 3,5

Pos

ition

/ nm

Länge [nm]

2time/ s

310,5 1,5 2,5 3,5

3

2

4

1

0

z =0,06 nm

y =0,09 nm

x =0,08 nm

Pos

ition

/ nm

x-axis

y-axis

z-axis

Stability of positioning (clodsed-loop control)

Stability of interferometers(deactivated drives)

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1. Laser focus probe with CCD camera microscope

Hologram laser unit

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Laser focus probe with CCD camera microscope

Microlens-array: 1 mm x 1 mmLens 25 mm x 25 mm (scanning time: 25 min)

Laser spot

Overview screen(800 µm x 600 µm)

Lateral resolution: 0.6 µm

0.6 µm

Focus probe• Single point sensor• Vertical resolution: < 1nm• High speed scanning: 6 mm/s • Measurement height: up to 5 mm• with standard deviation: ~ 1 nm

0.6 µm

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2. Stylus probe

Disadvantage of optical probes:•Diffraction effects at sharp edges•Optical phase shift errors

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Stylus probe in the NPM-Machine

Measuring Force: 0.9 mNDiamond tipped stylus: 2 µm/ 90°

Pick-up MarSurf MFW 1250

Step height measurement (70 nm)

0.6 µm

R=2 µm

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3. AFM-probe

Disadvantage of stylus probes:Large tip diameter

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Atomic force microscope probe

0.5µm

10nm

10 –

15 µ

m

Focus probe

Cantilever adapter

Piezo translator

Lens

Vertical resolution: < 1 nmLateral resolution: < 10 nmScanning speed: > 10 µm/s

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PTB-calibration

in nm

NMM-results

in nm

difference in nm

Pitchexp.

uncertainty Mode Pitchexp.

uncertainty

3000,37 0,042 1

AC-Mode 3000,350 0,022 2 0,02

DC-Mode 3000,361 0,022 2 0,009

(1 k=2, 2 30 repetitions, k=2)

AFM-Sensor – Pitch-Measurements

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4. White light interference microscope

Mirau interferometer

Area sensor!

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White light interferometer microscope

69 nm

Example:Measuring area: 4 x 4 mm2

Number of fields: 64Measuring time: 23 min.Data points: 21 mill.

In combination of stitching with nanometre accuracy(up to 25 mm x 25 mm)

Vertical resolution: < 1 nmLateral resolution: 0.8 µmZ-scan: 2 mill. data points in 20 s

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Comparison of different probes in the NPMM

Deviation from calibration value: h < ± 0.8 nm

Standard deviation of probes: u < 0.9 nm

67

68

69

70

71

Calibration value * Focus sensor Tactile stylus sensor AFM based on Focussensor

White-lightinterference sensor

Ste

p he

ight

in n

m

* Regarding the whole measuring field

Step height measurement

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-500 0 500 1000 1500 2000 2500 3000 3500 4000 4500-500

-400

-300

-200

-100

0

100

200

300

400

500

µm

µm

Focus sensor

Tactile stylus probe

PTB-Measurement

10 mm

Form measurement at steep flanks

PTB Micro Contour Standard Steep flanks can not be measured neither with laser focus probe nor with stylus probe

M. Neugebauer/ PTB

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5. CCD camera microscope combined with depth from focus method

beam splitter

collimator

light source

CCD camera

objective

Disadvantage of laser focus probe:Single point data collectionLimitation of slope angle

hologram-laser-unit

collimator

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Depth From Focus (DFF) Method

Micro contur standard 25 mm x 360 µm (Dr. Neugebauer/ PTB)90 stitched areas, 54.000 pictures, duration: 2.5 h, storage: 100 GByte

combined with high precision stitching

Single area: 360 µm x 360 µmZ-scan: 20 images/sStitching of single z-scans with nanometre precisionMeasurement of steep slopes (80°) on rough surfacesStandard deviation: up to 50 nm

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focus probe/CCD microscope

white light interference probe

focus lens

stylus

lever pivot

stylus probe AFM probe

cantilever

Mirauobjective

piezo translatorpiezo shaker

beam splitter

collimator

hologramlaser unit

light sourcecollimator

CCD camera

objective

LWDobjective

Multi-sensor approach on the base of laser focus probe

5 sensors on one stage

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Mechanical revolver

• Focus sensor• CCD-camera microscope• White light interference

microscope• Stylus probe

In preparation:• AFM probe• 3-D-MicroprobeMirau objective

Stylus probe

100x Objective

Multi-sensor-arrangement with microscope revolver

Fiducial marks necessary

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Large area AFM scan25 x 25 mm² /10 nm line spacing: 200 years

Cantilever

AFM camera image0.48 mm

0.65

mm

• ~2000 single camera shots (30 min, 3 Gpixel)

25 mm

Stitching (38x52 images)

• automatic stitching

AFM-Scans

• directed AFM scans in small fields of interest

180 nm

Segmentation

and segmentation

NT&D Nanotechnol & Devices

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3-D-Orientation (fast WLI)

• Z-scan (limited by camera: 45 Hz): 3 µm /second• Evaluation time: < 1 second (1032x768 Pixel)

Example: Stitching of 9 x 9 regions: 4 x 3 mm²Measurement points: > 50 Mio., < 25 seconds/ region: 0.5 h

Wafer - overview

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3-D-OrientationWafer 4 x 3 mm²

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3-D-microprobes integrated in NPM-Machine

NPL-probe (IBS Eindhoven)

3 copper beryllium flexures3 capacitive sensorsStiffness: 10 N/m (isotropic)Reproducibility: 4.3 nm

Ball diameter: 300 µmMeasuring force: 0.1 mN Freeform area scan (constant force):

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Multi-orientation Measurement of 3-D microstructures

3-D fiducial elements(ruby balls)

by rotation of the object

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Implementation of a rotary stage in the NPM-Machine

Rotary stage

Measuring table of NPM-machine

Fiducial elements (ruby balls)

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Conclusion

• Five different probing systems (with nanometre resolution) integrated in the NPM-machine

• Multi-sensor application on the base of a microscope revolver• Several measurement strategies for large area scans, steep

flanks and undercuts proposed and tested

Outlook

• Automatic probe charger (motorized revolver)• Improvement of fiducial mark technology• Improvement of large field measurements

Further developement:

••

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Acknowledgement

DFG: special research centre SFB 622: Nanopositioning and Nanomeasuring Machines

EU-FP6-project: NanoCMM, especially SIOS Messtechnik GmbH

all co-workers at Ilmenau University of Technology

SFB 622