High-resolution XRD characterization of SiGeC structures for high frequency microelectronics applications

It is demonstrated how high resolution X-ray diffractometry (XRD) in comparison to different other characterization techniques, reflectometry, spectroscopic ellipsometry, Auger electron spectroscopy, secondary ion mass spectroscopy, and transmission electron microscopy, can be used to analyze the layer properties of typical SiGeC hetero-bipolar transistor (HBT) structures. For three different HBT's the parameters of Si cap and total SiGeC layer thickness, and the maximum Ge content are measured and the error limits of the different techniques are discussed. The values obtained agree very well within the error limits. Concerning layer thickness an achievable accuracy of about 1 nm is realistic and reproducible in a routine process. The highest accuracy in Ge content determination of about 0.5% can be realized by XRD and well-calibrated spectroscopic ellipsometry. XRD measurements in small (0.5 × 0.5 mm2) structures show comparable results with a laboratory source and synchrotron radiation.