Reviewed are the principles and applications of sputter depth profiling for the analysis of semiconductor and microelectronic materials. Various techniques are based on sputter removal whereby either the sputtered species (in SIMS, SCANIIR) or the remaining surface (AES, XPS, ISS) are investigated. In spite of its increasing importance, there are many problems associated with sputter etching. After a general survey of the principles, a detailed discussion is devoted to the many effects which can distort sputter depth profiles and limit depth resolution. These effects can be caused by instrumental factors (nonuniformity of erosion, beam impurities, vacuum contaminants) and the sample composition or can be due to the analysis method used (information depth, matrix effects, detection limit, sample consumption). Most important are the effects caused by the sputtering ion beam itself. Among these are notably preferential sputtering, atomic mixing, surface roughness as a result of the sputter process, sample charging, surface transport, and chemical reduction. The review of applications concentrates on the measurement of the distribution of dopants and impurities in semiconductors, on the study of insulating films (in particular the Si/SiO~ interface and the oxidation of GaAs), and on the metallization problem in Si and GaAs technology.The ever-increasing miniaturization of electronic devices in VLSIC technology (1) places new demands on analytical techniques for their characterization (2, 3). Of special interest is the measurement of elemental distributions, in particular the measurement of dopant distributions in the semiconductor substrate (4, 5) and the analysis of diffusive and reactive processes between metal, semiconductor, and dielectric films (6, 7) which are the basic elements of microelectronic structures. The analytical requirements for measurement techniques include good spatial resolution as well as elemental sensitivity and specificity. Although there are interesting questions to be asked with respect to lateral dimensions, because of the planar structure of most microelectronic devices, methods for the measurement of elemental concentrations as a function of depth are of special importance. An example for the requirements for the depth resolution of such methods is given in Fig. 1 which shows calculated depth distributions of dopants in base and camel collector of a monolithic hot electron transistor (MHET) with an extremely shallow barrier raising implant.An overview of methods for the measurement of depth profiles is given in Table I. The so-called nondestructive techniques are so named n~t because they necessarily leave the sample undamaged, but because the sample surface does not have to be removed in order to obtain information about the inside. The sample interior is rather probed with penetrating ion or electron beams whereby the depth information is obtained via the energy loss experienced by the particles while traversing the sample. Rutherford backscattering spectroscopy (RBS) is based on the ...
