nanostation 300: system for scanning probe metrology on larger … · - system for spm metrology on...

Physikalisch-Technische Bundesanstalt, Braunschweig und BerlinWorking group 5.22 in cooperation with Surface Imaging Systems

Nanostation 300: System for scanning probe metrology on larger objects

Travel range: 300 mm x 550 mm; el.-magnetic linear direct drives

Feedback control by encoder systems with < 10 nm resolution

Position deviations after correction of reproducible errors: < 1 µm

Objectives:

- System for SPM metrology on 300 mm objects

- Sample navigation: opt. microscopes and SPM

- Automatic measurement incl. tip reconstruction

- Use of air bearing x-y-stage and stable granite base

- Flexibility with respect to different SPM modi

- System upgradeable: 6 axis piezo scanning stage

- System upgradeable: x-y-laser interferometry

Nanostation 300 in PTB clean room centre Nanostation 300: SPM z-stability

SPM tip reconstruction

Microscopic structure localisation

SPM contact mode measurements on etched Si (111) faces

Use of non-contact SPM mode with EBD C-needle cantilever:

Control paramater setting influences obtainable edge resolution

Wrong setting of control parameters can damage sensitive tips

Edge measurement requires application of dedicated scanning modi

Different microscopes for structure localization:

Coarse ( and fine microscope (0.7

High resolution microscope: 85 µm x 65 µm, 117 nm pixelsize

Optical feature localisation to define batch AFM measurements

4 mm x 3 mm) mm x 0.5 mm)

Stage characteristics

Straightness deviation in y-direction: 1.2´´, hysteresis of 0.4´´

Straightness deviation in x-direction: 4´´, no hysteresis

Stage positioning noise at target position currently 70 nm (2s)

Further decrease possible by controlled reduction of air gap

yaw vs. position along y-axis

-0,8

-0,4

0

0,4

0,8

-0,3 -0,15 0 0,15 0,3

y position [m]

yaw

[arc

sec]

yaw vs. position along x-axis

-4

-2

0

2

-0,15 -0,1 -0,05 0 0,05 0,1 0,15

x position [m]

yaw

[arc

sec]

Profile through atomic Si steps

-0,2

-0,1

0

0,1

0,2

0 1000 2000 3000 4000 5000x position [nm]

heig

ht

[nm

]

sensor noise in z

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0 0.2 0.4 0.6 0.8 1

position [nm]

he

igh

t[n

m]

SPM measurement in contact: z- noise < 0.06 nmspot mode

Edge detection and control parameters

2D Graph 4

X Position [nm]

-20 -10 0 10 20

Z[n

m]

0

2

4

6

8

10

SPM tip reconstruction method by use of Au nanospheres:

Reconstruct the 3D tip shape from several 1D profiles

Scanning probe microscope

Reference samples

Optical microscope

Mask object

Object frame

Air bearing x-y-stage

26,7° 24,1°26,7° 24,1°

49,2° 46,9°49,2° 46,9°

59,3° 61,7°

artefact

59,3° 61,7°

artefact

Use of carbon-needle cantilever,variation of damping parameters:above: 60% remaining amplitude => low resolutionmiddle: 53% => optimum resolutionbottom: 50% => severe tip wear