Characterization of epitaxial SiGe thin films on Si: Analytical considerations

Epitaxial silicon—germanium (SiGe) thin films are being developed for a number of interesting applications. Potential uses include applications as fabrication layers for heterojunction bipolar transistor devices and a number of other novel electronic devices. For device applications, SiGe structures offer the potential for increased speed, bandgap engineering, rapid oxide growth and low processing temperatures. For electronic device applications, successful fabrication of SiGe films with the desired properties requires a thorough understanding of deposition, oxidation, interdiffusion and interface behavior. This paper details the analytical methods employed to characterize SiGe thin films deposited in various molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) reactor systems. Rutherford backscattering spectrometry (RBS), secondary ion mass spectrometry (SIMS), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) are used to study both the as‐deposited and oxidized films. Determination of Ge content and distribution, measurement of dopant concentrations within the SiGe, build‐up of Ge at oxide interfaces, build‐up of oxygen at interlayer interfaces and film thickness measurements will be illustrated. Methods for the cross‐correlation and calibration of the various instrumental techniques and use of the characterization data to optimize processing conditions will also be discussed.