Presented for CMA Analytical Workshop 2012Neal Leddy

surface metrology

ApplicationsRoughness Lay Waviness Form

Flatness 3D analysis Step Height Film thicknessFeature measurementRadius of curvature

techniques

Tactile Stylus Atomic force microscopy

Optical White light/Laser interferometry Confocal microscopy Ellipsometry Focus variation

probe

cantilever Diamond stylus

white light (filtered light)laserelectron beam

piezo electric actuators

the linear electromechanical interaction between mechanical and electrical state in crystalline material.

reversible

examples - lead zirconium titinate, quartz

detector

laser & photodiode

ccd camera

stylus

Diamond probe contacts sample surface Tip size: >20nm ~ 25um Direct measurement

Disadvantages contact method, generally single line,Advantages fast, widely accepted, reasonable z resolution

afm

Cantilever tip

Contact mode Non-contact mode Tapping mode Force modulation Phase imaging

Local friction imaging Surface potential imaging Electrical conductivity imaging Magnetic and electric field imaging Thermal conductivity mapping Temperature mapping Modulus mapping

Disadvantages limited sampling area, limited z range, slow scan speed.

Advantages high resolution, 3 dimensional, large sample area and vertical range (>10mm)

Cantilever silicon/silicon nitride

Piezoelectric actuator

Laser

Detector photodiode

wli

White light source Resolutiuon 0.01 nm

Scanning mode Phase shift mode

Disadvantages requires reflective surface, lateral resolution (diffraction limit) ~500nmAdvantages high resolution, 3 dimensional, large sample area and vertical range (>10mm)

wli

white light source

Beam-splitter

reference mirror

interference objective

piezo electric stage

ccd camera

confocal

Typical Scan area: 200 mm X 200 mm X Resolution: 30 nm to 3 um Z Range: 300 um to 30 mm

Disadvantages limited z resolution.Advantages High vertical scan depth, fast measurement speed.

ellipsometry

Change in polarisation of light reflected/transmitted from a sample structure. response is dependent on optical properties and thickness of each material.

film thickness optical constantscharacterise composition, crystallinity, roughness, doping concentration,

Disadvantages limited sample applicabilityAdvantages transparent films (resolution 1nm ~ 10-15mm)

Light source

Polarizer

(Optional compensator)

Surface reflection

(Optional compensator)

Analyzer (2nd polariszer)

Detector (voltage)

focus variation

Using optics with very little depth of field. Realised using microscopy like optics and a microscope objective. These objectives have a high numerical aperture which gives a small depth of field.sample or optics moved in relation to each other.at each position the focus over each plane is calculatedthe plane with the best focus gives the depth at that position

Disadvantages resolution (30nm), flat surfaces (requires form)Advantages Large scan range, Good for very rough surfaces

summary of optical

techniques

other techniques

3D stereoscopic reconstruction Stereo pair Scanning Electron Microscope

tilted with eucentric stage. Algorhitm reconstructs 3d image.

Disadvantages relies on good stereo pairs, limited z resolution, requires structured surfaceAdvantages high magnifications

Isotropic vs. anisotropic

IsotropySurface presents the same characteristics regardless of the measurement direction, i.e. surfaces with a random texture without any distinction or direction

anisotropySurfaces encountered with machined or formed features will have a direction or periodic structure

Isotropic anisotropic

roughness

Describes the texture of a surface. It is measure of the vertical deviations of a real surface from its ideal form.

Roughness: high frequency and short wavelength

Largely related to surface interactions.

waviness

Describes the surface form.

Waviness: low frequency and usually long wavelength

Generally a result of manufacture

roughness standards

ASME B46

ISO 4287 profile ISO 12085 ISO 13565

ISO 25178 aeral surface

Geometrical Product Specifications and Verification

surface amplitudeSymbol Name 2D Unit 3D

Sa Roughness Average DIN 4768 ASME B46.1 [nm] ISO/DIS 25178-2ASME B46.1

Sq Root Mean Square (RMS)

ISO 4287/1 ASME B46.1 [nm] ISO/DIS 25178-2ASME B46.1

Ssk Surface Skewness ISO 4287/1ASME B46.1

ISO/DIS 25178-2ASME B46.1

Sku Surface Kurtosis ANSI B.46.1ASME B46.1

ISO/DIS 25178-2ASME B46.1

Sz Peak-Peak ISO 4287/1 [nm] ISO/DIS 25178-2

St Peak-Peak ASME B46.1 [nm] ASME B46.1

Sy Peak-Peak [nm]

S10z Ten Point Height ANSI B.46.1 [nm] ISO/DIS 25178-2ASME B46.1

Sv Max Valley Depth ASME B46.1 ISO/DIS 25178-2ASME

Sp Max Peak Height ASME B46.1 ISO/DIS 25178-2

ASME B46.1

surface hybridSymbol Name 2D Unit 3D

Ssc Mean Summit Curvature [1/nm]

Sti Texture Index

Sdq Root Mean Square Gradient

ISO/DIS 25178-2

Sdq6 Area Root Mean Square Slope

ASME B46.1

Sdr Surface Area Ratio ISO/DIS 25178-2

S2A Projected Area nm^2

S3A Surface Area nm^2

Functional parametersSymbol Name 2D Unit 3D

Sbi Surface Bearing Index

Sci Core Fluid Retention Index

Svi Valley Fluid Retention Index

Spk Reduced Summit Height DIN 4776 [nm]

Sk Core Roughness Depth DIN 4776 [nm]

Svk Reduced Valley Depth DIN 4776 [nm]

Scl-h l-h% height intervals of Bearing Curve

ISO 4287 [nm]

Spatial parametersSymbol Name 2D Unit 3D

Sds Density of Summits ASME B46.1[6]

Std Texture Direction [deg] [6]

Stdi Texture Direction Index [7]

Srw Dominant Radial Wave Length

[nm] [7]

Srwi Radial Wave Index [7]

dShw Mean Half Wavelength [nm]

Sfd Fractal Dimension

Scl20 Correlation Length at 20%

Scl37 Correlation Length at 37%

Str20 Texture Aspect Ratio at 20%

Str37 Texture Aspect Ratio at 37%

Symbol Name 2D Unit 3D

bearing ratio

Mathematically it is the cumulative probability density function of the surface profile height

calculated by integrating the profile trace

White light interferometry

omniscan microXam

Scanning wli

Surface roughnessShot Peened Steel:

Surface map 3D Surface

Profile roughness (2d)

Surface roughness (3d)

Profile through origin

Rq/Ra = 1.22

Rq/Ra = 1.25

Rq is more sensitive to peaks and valleys than Ra, as amplitudes are squared.

Typically for classic surface Rq = 1.1(Ra)

surface filteringPrimary surface waviness roughness

Primary surface profile waviness profile roughness profile

primary surface waviness surface roughness surface

primary profile waviness profile roughness profile

step height

Step height standard:Nominal : 8.18 umActual : 8.181um

film thickness

advanced feature analysis Vickers indent:

vickers indent profile

vickers indent calculated hardness

phase mode

Phase mode utilizes narrowly filtered light to perform a phase shifting of light fringes for acquisition

Achieved by phase shifting one of the interfering beams along the optical axis.

Reduces system noise and gives best results for very flat samples.

phase mode

3D Stereoscopic reconstruction

2d sem image of shot peened steel

5tilt @ working distance

~10mm

mex vs wli

3d SEM reconstruction White light interferometry

Nettle leaf Nettle leaf reconstructed tilt series

Flower detail reconstructed tilt seriesFlower detail