Specific Process Knowledge/Characterization/AFM: Atomic Force Microscopy/AFM Icon Acceptance

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This page has been made by Berit Herstrøm @ DTU Nanolab

Accessories following the systems

Equipment	AFM Icon	AFM Icon 2
Chucks	A symmetric chuck that handles up to 210mm wafers and 15mm thick An asymmetric chuck that handles up to ~4" wafer (but not small pieces) - using this a whole 4" can be accessed without rotating the sample.	A symmetric chuck that handles up to 210mm wafers and 15mm thick
Holders	Magnetic sample holder + magnetic discs + double sided tape Holder for vertical profile scans	Magnetic sample holder + magnetic discs + double sided tape Holder for vertical profile scans ?
Modes included	PeakForce Tapping mode / ScanAsyst TappingMode (air) Contact Mode Lateral Force Microscopy Phase Imaging Lift mode MFM Force Spectroscopy Force volume EFM surface potential Torsional Resonance Mode Piezoresponse Microscopy Force spectroscopy Extra modes: PeakForce KPFM package (incl extra box for high voltage PF KPFM) PFQNM package Microscope Image Registration and Overlay (MIRO) software. this is only working in the old software (before version 9.4)	PeakForce Tapping mode / ScanAsyst TappingMode (air) Contact Mode Lateral Force Microscopy Phase Imaging Lift mode Force Spectroscopy Force volume surface potential Torsional Resonance Mode Piezoresponse Microscopy Force spectroscopy
Probes that followed the systems	ScanAsyst mode Tapping mode Contact mode PF-KPFM ScanAsyst air 30ps ScanAsyst fluid 10ps ScanAsyst fluid + 10ps MPP-11100-10 MPP-21100-10 MPP-11120-10 RTESPA TESPA-V2 10ps OTESPA-R3 10ps High Aspect ratio probes 1:15: FIB6-400A 5ps MPP-12120 10ps. Tap150A MPP-13120-10 TAP525A SNL-10 20ps SCM-PIT 10ps PFQNE-Al 10ps	ScanAsyst mode Tapping mode Contact mode ScanAsyst air 20ps ScanAsyst fluid 10ps ScanAsyst fluid + 10ps RTESP-300 (like MPP-11100-10) RFESP-75 (like MPP-21100-10) TESPA-V2 10ps OTESPA-R3 10ps NCHV 10ps SNL-10 20ps
Samples	QC grid: VGRP-15M 10µm pitch and depth reference 178nm PF KPFM-SMPL Kelvin probe Sample: Al + Au on Si HOPG: Highly Oriented Pyrolytic Graphite Calibration samples for getting quantitative modulus measurements: PDMS-soft-1-12M: PDMS gel 2.5MPa PDMS-soft-2-12M: PDMS gel 3.5MPa PSFilm-12M: Polystyrene filem FSilica-12M: Fused Silica Sapphire-12M: Sapphire RS-12M: Ti roughness sample HOPG-12M: Highly Orientated Pyrolytic Graphite PS-LDPE: Harmonix training	QC grid: VGRP-15M 10µm pitch and depth reference 181nm HOPG: Highly Oriented Pyrolytic Graphite

AFM Icon-Pt 1: Acceptance tests done

Noise tests

Sensor noise

Tappingmode, OTESPA-R3 probe used.
First we made a false engage (scanning in air): Turn off gain 0 0
Z range 0.2my
Scan size 0.01nm
We saw some 50Hz noise (electrical - or maybe pumps): Rq 15 pm (specs 35pm)

System noise

Noise on sample: scan size 0.1nm
we started with 1my scan size to optimize the scan.
2.43Hz
256 lines
Z range at 2my to get sub nanometer resolution in Z
Rq: 54,5pm (plade vibrator koerte udenfor)
Rq: 23pm uden vibrator koerende + ro og med aaben hood.
Rq:71pm uden vibrator koerende + ro og med lukket hood

Roughness

HAR: 200nm wide 400nm deep

Graphene KPFM measurement

Height image: The graphene and structuring in graphene is not visible
Potential image: Potential difference between grapheme and non-graphene is visible
Phase: Phase imaging maps the phase lag between the periodic signal driving the cantilever and the oscillations of the cantilever. Changes in phase lag often indicate changes in the properties of the sample surface. Here the structuring in the graphene is very clear

AFM Icon-Pt 2: Acceptance test

Noise tests

Sensor noise

Tapping ]mode, OTESPA-R3 probe used.
First we made a false engage (scanning in air): Turn off gain 0 0
Z range 0.2my
Scan size 0.01nm
Roughness: Rq 28 pm (specs 35pm)

System noise

Noise on sample: scan size 0.1nm
we started with 1my scan size to optimize the scan.
2.43Hz
256 lines
Z range at 2my to get sub nanometer resolution in Z
Rq: 28 pm

Demonstrating roughness measurements on silicon

ScanAsyst with ScanAsyst-air

• CL on
• 512x512
• 0dg
• ScanAsyst noise threshold: 1
• PeakForce amplitide 300 nm
• Peak force frequency: 2 Hz
• Rq: 0.247 nm

ScanAsyst with ScanAsyst-air

• CL off
• 512x512
• 0dg
• ScanAsyst noise threshold: 0.2
• PeakForce amplitide 300 nm
• Peak force frequency: 2 Hz
• Rq: 0.235 nm

ScanAsyst with TAP150A

• CL on
• 512x512
• 0dg
• ScanAsyst noise threshold: 1
• PeakForce amplitude 75 nm (was set as standard from the probe settings)
• Peak force frequency: 2 Hz
• Rq: 0.238/0.250 nm

Tapping mode with TAP150A

• CL on
• 512x512
• 0dg
• Rq: 0.214 nm

Tapping mode with RFESP-75

• CL on
• 512x512
• 0dg
• Rq: 0.224 nm

Step measurement: Resist on silicon oxide

SIO2ICP_30 (Si-SiO2-Resist)

• When scanning long lines and trenches scan 90 degrees to the probe and 90 degrees to the lines.
• During acceptance:
  • Tapping mode: 3 µm structures (middle): 1.587µm
  • Tapping mode: 3µm structures (edge): 1.541µm
  • Peak Force tapping 3µm structures (edge) average: 1.497µm (tapping mode probe)
  • Peak Force tapping with ScanAsyst probe: 1.509µm

SEM images showed about 1.55µm – so it seems like ScanAsyst is pressing a little down in the resist compared with the SiO2 giving a too small height difference. Therefor When scanning steps with difference materials, when one of the materials is soft and you need to know the height difference, then it seems to be best to use tapping mode. We did not save the images. Therefor I remeasured a few days later:

Tapping mode with TAP150A

• CL on
• 256x32
• 0dg
• Step height: 1545/1532 nm

ScanAsyst with TAP150A

• CL on
• 256x32
• 0dg
• ScanAsyst noise threshold: 1
• PeakForce amplitide 75 nm (was set as standard from the probe settings)
• Peak force frequency: 2 Hz
• Step height: 1537 nm

ScanAsyst with ScanAsyst-air

• CL on
• 256x32
• 0dg
• ScanAsyst noise threshold: 1
• PeakForce amplitide 150 nm (I had to increase it from the 75 nm)
• Peak force frequency: 2 Hz
• Step height: 1545 nm

Tapping mode with RFESP-75

• CL on
• 256*32
• 0dg
• Step height: 1525 nm

High Aspect ratio sample

High aspect ratio samples (e.g. 100 nm wide trenches 300 nm deep and 2 µm wide trenches 6µm deep). The probes for this: FIB6-400A. This was done and work spaces were created but no images was saved.