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