Optical profilometry

X-Ray Reflectometry (XRR) analysis is used to measure the density (g/cm3), thickness (nm), and roughness (nm) of thin films. The method is applicable to the characterization of single- or multilayered thin films, as it provides information on the thickness and density of individual layers of the sample material as well as the roughness of the interphases. Greatest accuracy for XRR thickness measurements is generally achieved for samples containing 1-150 nm thick surface layers with under 5 nm RMS roughness. Thicker films and coatings with rougher surfaces can also be characterized, but the accuracy of thickness determination decreases as the thickness and roughness of the film or film stack increase. >150 mm wafers are typically cut to fit the sample holder. Please let us know if you need testing for larger wafers that cannot be cut into pieces. The available temperature range for XRR measurements is 25-1100 °C, and crystallinity can be studied as a function of temperature. The measurements can be performed under a normal atmosphere, inert gas, or vacuum. Measurements are typically performed using one of the following instruments: Rigaku SmartLab, Panalytical X'Pert Pro MRD, Bruker D8 Discover. Please let us know if you have a preference for a specific instrument.

XPS is a semi-quantitative technique used to measure the elemental composition of material surfaces. In addition, it can also determine the binding state of the atoms. XPS is a surface-sensitive technique. Typical probing depth is 3-9 nm, and detection limits range roughly between 0.1 and 1 atomic %. XPS can measure elements from Li to U. The elemental composition is reported in at.% and measured on 1 area of a few 100 µm. Upon request, we can measure smaller areas or depth profiles, and a binding state determination can also be provided. Measurements are typically performed using one of the following instruments: PHI Genesis, Thermo Fisher ESCALAB 250Xi, PHI Quantum 2000. Synchrotron XPS is also available. Contact us for more information and a quote for your project.

Group delay dispersion (GDD) and group velocity dispersion (GVD) are critical parameters for understanding how the propagation time and speed of light pulses change with frequency or wavelength as they travel through transmitting media, such as glass optics, or interact within the layers of thin-film coatings. Group delay refers to the time delay experienced by light of various frequencies, while group velocity is the speed at which the envelope of a pulse propagates through a medium. GDD and GVD characterize the rate at which group delay and group velocity, respectively, vary with the frequency or wavelength of light. GDD and GVD are expressed in units of time squared, typically in femtoseconds squared (fs2). Both can be measured using a white light interferometer. The measurement conditions for which we can perform the test are outlined below. For a 1" sample Reflection optics AOI: 0° & 5-70°, Transmission AOI: 0-70°. For a 2" sample Reflection optics AOI: 5-70° (0° could be possible, discuss with expert), Transmission AOI: 0-70°. Spectral coverage: 400-1060 nm (VIS/NIR basic version), 250-1060 nm (UV/VIS/NIR version), 900-2400 nm (IR version). To carry out the testing, the following measurement details and sample information should be available: Sample matrix: Substrates, coating, etc. , Reflection/transmission angle of incidence: Reflection AOI of 45°, Transmission AOI of 45°, etc., Polarization: p, s, N/A, Working wavelength range, Measurement points: How many and where in the sample?, Expected GDD/GVD.

The focused ion beam (FIB) technique is used to prepare samples for electron microscopy. It allows very precise cutting of samples to observe them by TEM or SEM imaging. We are happy to provide a quote for FIB preparation on its own, as well as FIB-TEM or FIB-SEM analysis.

Auger Electron Spectroscopy (AES) is a surface-sensitive technique (3-9 nm) used for compositional analysis and depth profiling, providing data on the elemental composition in depth. Secondary electron images can also be provided. AES is a very useful technique to measure patterns since it has a beam size that can go down to a few nm.

Imaging of the sample using scanning electron microscopy (SEM). Typically, several images are taken with varying magnifications to get a good overview of the sample. Non-conductive samples can be prepared with a metallic coating to allow imaging. For cross-section measurement, additional preparation might be needed: FIB, BIB or freeze fracturing. If compositional analysis is also needed, please see the SEM-EDX measurement.

In XPS depth profiling, ion gun etching cycles and XPS analysis cycles are alternated to obtain semi-quantitative information on the elemental composition (at.%) of the sample as a function of depth. The binding states of atoms can also be analyzed as a function of depth to determine the chemistry of the sample and its variations with depth. XPS depth profiling is a destructive technique with an analysis area diameter ranging from 10 µm to several 100 µm. Sputtering is done with an Ar-cluster GCIB ion beam or Ar monoatomic ions, and XPS measurements are typically performed using one of the following instruments: PHI Genesis, Thermo Fisher ESCALAB 250Xi, PHI Quantum 2000.

Imaging of the sample using a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX or EDS). Typically, several images are taken with varying magnifications to get a good overview of the sample. An EDX mapping, line scan, or point measurement is collected to measure the sample composition (elemental at.% or wt.%). Non-conductive samples can be prepared with a metallic coating. For cross-section measurement, additional preparation might be needed: FIB, BIB, or freeze fracturing.

During this analysis, the surface of a smooth and hard sample is imaged with an atomic force microscope (AFM). Topological images are typically provided from three locations around the sample. The measurement area is 5 x 5 micrometers, if not otherwise agreed. Measurements are typically done using the following instrument: Bruker Dimension Icon.

Rutherford Backscattering Spectrometry (RBS) can be used to measure the composition of solid samples quantitatively at the surface as well as depth profiling. RBS is used for the analysis of heavy elements and can be combined with ToF-ERDA when lighter elements also need to be analyzed. Elements with similar mass can be difficult to differentiate.