Thin film characterization
X-ray reflectometry (XRR) is a non-destructive analytical technique suitable for structural characterization of surfaces and layered thin-film structures.
The method involves measurement of the intensity of the X-ray beam reflected by a sample. From these reflectivity measurements, information such as the film thickness, surface/interface roughness and density can be obtained.
XRR can be performed with high-energy (8.048 keV) or low-energy X-rays (1.487 keV). It requires minimal or no sample preparation and can be performed on irregular and large samples.
X-ray Photoelectron Spectroscopy (XPS) can be used as complement to XRR to study the chemical composition. XRR can be used in combination with Atomic Force Microscopy (AFM) as complementary tools to characterize the surface morphology.
Atomic Force Microscopy
Atomic Force Microscopy (AFM) is a technique used to measure the surface topography of materials in a nanometer resolution. It is a type of scanning probe microscopy where a small, sharp tip is scanned across the sample surface to map the contours and generate three-dimensional surface profiles of the sample. AFM can map the topography with a scan size up to around 90 µm x 90 µm and has a vertical range of 12 µm.
AFM can be used in combination with X-ray Reflectometry (XRR) as complementary methods for characterizing surface roughness.
X-ray Photoelectron Spectroscopy
X-ray Photoelectron Spectroscopy (XPS) is an elemental analysis technique widely used to determine the atomic composition and can provide information on the chemical state of the detected elements in the near-surface region which extends to a depth of approximately 10 nm.
Ion beam etching can be used to slowly remove thin layers of material from the surface. The repeated sequence of etching and subsequently collecting the spectra of the newly exposed surface produces XPS depth profiles with the elemental composition as a function of penetration depth.
XPS depth profiles of multilayer structures can be used in combination with X-ray Reflectometry (XRR) which allows a more precise determination of layer thickness and density. XPS can be used in combination with Atomic Force Microscopy (AFM) as complementary tools to characterize the surface morphology.
Scanning Electron Microscopy
Scanning Electron Microscopy (SEM) is a technique that scans a sample using a focused beam of high-energy electrons to produce images of topographical features on the sample surface at the nanometer scale. It allows detection of contaminates and evaluation of fractures or flaws on the surface. The output from SEM is three-dimensional images.
SEM can be used in combination with Atomic Force Microscopy (AFM) which provides height information of the surface. This makes it easier to determine if a surface feature is sloping up or down, and it can be used to determine the surface roughness.
X-ray Photoelectron Spectroscopy (XPS) can also be used as complement to SEM to study the chemical profile of the surface defect.