X-Ray Diffractometer

The X-Ray diffractometer is used to determine the crystallographic orientation of a wafer or grown ingot by bouncing x-rays off of a sample toward a detector that is positioned at a known angle.  The sample is systematically moved until  the beam strikes the detector.  This method is used to correct misorientations prior to wafer production.  Also, X-Ray rocking curves can be made that estimate crystalline quality.

AFM

Atomic force microscopy is a technique that uses a atomic scale probe tip to trace the surface of a sample thereby characterizing the samples topography.  The AFM is used to determine average roughness of polished wafers and films.  Also, the AFM may be used for another technique called SCM, or scanning capacitance microscopy.  This technique is used to reveal position relative electrical characteristics of a sample.

SEM

The Scanning Electron Microscope can be used to examine small surface features.  More importantly, if operated in EBIC mode, the system can be used to see defects in a nondestructive manner.  EBIC stands for electron beam induced current.  A device such as a p-n diode may be put under bias in this system and stacking fault propagation can be seen in real time.

Elipsometer

The Elipsometer is used to measure the thickness of oxide layers.  It does so my using the difference in the index of refraction between SiO2 and SiC.  Light entry and exit angles are measured to deduce thickness.

Profilometer

The profilometer is similar to AFM.  A probe tip scans the surface measuring topography.  This system is useful for measuring film thickness and step height but the resolution is inferior to AFM.

Nitrogen Laser Lifetime Measurement

This system is used to determine the carrier lifetime using photoconductive decay.  Carriers are excited using a nitrogen laser at 337nm.

Raman

Raman spectral analysis is used to view the spectrum produced due to Raman scattering.  This spectrum can be used to distinguish between different materials, including the different polytypes of SiC.  The Raman system was built here at USC.

PLM

The polarized light microscopy system allows us to view stress patterns in SiC material.  These patterns correspond to known defects.  The PLM system that was built at USC can automaticlally scan an entire 3" wafer and pattern recognition software can identify and count defects.

CV

Our mercury probe capacitance-voltage measurement setup allows us to determine the doping density in epilayers by measuring the capacitance as a function of reverse bias.

Another CV setup is used to measure interface trap density in SiC MOS capacitors.

I-V Measurement

The current-voltage measurement setup allows us to characterize the performance of Schottky and PiN Diodes in terms of forward voltage drop and reverse leakage current.

Hall Measurement

The hall measurement system is used to characterize the mobility and carrier density of diffused SiC diodes.

DLTS

Deep level transient spectroscopy is used to find the deep level trap states in the bandgap of SiC bulk material and epilayers.

Wet Etching using Molten KOH

Molten potassium hydroxide is used to delineate defects in SiC.  The aggressive etchant preferentially etches highly stressed regions surrounding dislocations making recognizable patterns that can be associated with different types of defects.

Nomarski Imaging

Nomarski contrast mode imaging is used in conjunction with an optical microscope to increase the contrast of surface irregularities like scratch marks.

Anodic Oxidation

The anodic oxidation setup is used to measure epilayer thickness.  A cleaved sample is oxidized and the difference in doping concentration of substrate and epilayer causes a change in oxidation rate.  This results in a demarcation of the epilayer substrate interface by a sharp color contrast that allows the thickness to be measured using a microscope.

The sample shown here has been subjected to KOH etching as well as anodic oxidation.