IN-SITU ELLIPSOMETRY OF SOFT-X-RAY MULTILAYER FABRICATION

In situ ellipsometry is applied for monitoring soft X-ray multilayer f abrication. With a homogeneous single-layer model, variations in compl ex refractive indices and thicknesses were studied with the growth of single layers. After initially anomalous behaviour, minimum critical t hicknesses of optical ideality of ultrathin Au and Mo layers formed by electron beam deposition were found to be 13 nm and 5.0 nm, which wer e much larger than 5.8 nm and 3.3 nm obtained by ion beam sputtering. The complex refractive indices obtained were used for simulation of pe riodic multilayer growth, which showed that ideal growth was expected to appear as a segment in a complex plane plot of relative amplitude a ttenuation rho. With this knowledge, the experimental result in the ca se of an Au-C multilayer was understood: island structure growth of Au took place on every C layer and also, on every Au layer, C initially formed a mixed layer of thickness around 0.5 nm.