Surface and Thin Film Compositional Analysis: Description and Comparison of Techniques Available to Purchase

The materials analyst today has available to him techniques for characterizing the three-dimensional elemental composition of a sample, some of which give a lateral spatir¹  resolution on the order of 1 µm and all of which give a depth resolution of ~200 Å or less. The development of these powerful techniques has been stimulated by the move to thin-film technology in the semiconductor industry and by the growing technological importance of such phenomena as corrosion, embrittlement, and catalysis. In all these areas the composition and properties of surfaces determine many of the properties of materials. The earliest microanalytical technique was the electron microprobe, which made possible analyses with lateral (x, y) and depth (z) resolutions of about 1 µm. The 1960’s saw the development of electron spectroscopies (ESCA, Auger) and secondary ion mass spectrometry (SIMS) which are sensitive to the outer 10-20 Å of a sample (i.e., have a shallow escape depth for the analytical signal). The coupling of these spectroscopies with sputtering (sputtering is, of course, intrinsic in the SIMS technique) allows the characterization of successive 10-20 Å layers as sputtering erodes the sample. Lateral (x, y) resolution is attained in the charged particle-induced spectroscopies by using a microfocused primary beam (Auger, ion microprobe) or by ion optically locating the origin of the secondary signal (ion microscope).