Precise Measurement of Ge Depth Profiles in SiGe HBT's - a Comparison of Different Methods

We demonstrate how different characterization techniques, X-ray diffractometry and re-flectometry, spectroscopic ellipsometry, Auger electron spectroscopy, secondary ion mass spectros-copy, and transmission electron microscopy, can be used to analyze the layer properties of typical SiGe Hetero-Bipolar Transistor (HBT) structures. For three different HBT’s the parameters of Si cap and total SiGe layer thickness, maximum Ge content, and shape of the Ge gradient part are measured and the error limits of the different techniques are discussed. We show that 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 SE.