(in collaboration with ON Semiconductor)
We have developed specific methodology for SiC wafers analysis, emplying surface sensitive techniques we have extensive expertise in.
Raman spectroscopy for polytype identification
Raman analysis is ideal to identify polytypes with SiC wafer, including mapping of the wafer surface (wafer scale analysis).
SiC analysis by X-Ray Photoelectron spectroscopy
Si-C bonding shows off in Si 2p peak as a component between 100.5-101 eV (the pure Si peak position being 99.4 eV), it can be fitted as slightly asymmetric Voight function. The spectrum below shows a freshly cleaved sample, where only slight oxidation occurred. In C1s peak, Si-C bonding is manifested by a single component at 283 eV, at lower binding energy side to adventitious carbon at 284.8 eV. The component is a symmetrical Voight function.
XPS combines high surface sensitivity with the capability to distinguish the chemical state of the elements on the surface.
Secondary Ion Mass Spectroscopy for SiC analysis
SIMS is unrivalled in capability of detecting dopants and contamination down to extremely low concentrations. Our instrumentation allows 3D profiling of selected elements within the wafer. The depth profile below shows the position of Nitrogen atom dopants within SiC wafer.
Atomic Force Microscopy for SiC wafer roughness analysis
Careful tuning of scanning parameters allows to analyze SiC wafers at different stages of polishing, exhibiting various roughness.
Spectroscopic Ellipsometry for analysis of etching processes on SiC
Spectroscopic ellipsometry could be used to support the development of chemical etching and passivation approaches to SiC. It is very sensitive to surface state (see below, wafers processed for different time by SC1 treatment), and we concluded that Delta parameter is the most appropriate one for SiC, giving (indirectly) also the information on oxide thickness (this comes from fitting utilizing a standard model of SiO2 on SiC bulk).
Kelvin probe force microscopy
This technique allows to map local surface potential variations on SiC wafer surface. Although it is not able to distinguish between different SiC polytypes, its application to local structural defects shows interesting details on electronic structure in the defect vicinity. The results below show potential charge accumulation in the defect region, making the defect detrimental for applications defective wafers in electronics.