Atomic Layer Deposited Al2O3 as Characterized Reference Samples for Nanolayer Metrology

Plasma assisted Atomic Layer Deposition Al2O3 samples were studied using an approach of complementary metrology using Ellipsometry, X-Ray Reflectivity, Atomic Force Microscopy, and Total Reflection X-Ray Fluorescence. For modeling the samples, an interfacial rough SiO2 layer has to be assumed. The excellent linearity of the ALD process was used to cross check Ellipsometry and X-Ray Reflectivity. In contrast to Ellipsometry, X-Ray Reflectivity showed a residual surface layer, identified as chlorine contaminated layer by TXRF. The samples are shown to be ideal candidates for calibration of X-ray fluorescence as the Al signal linearly depends on the film thickness or ALD cycles. Furthermore, the impact of self-absorption of thick layers for TXRF was shown by the samples.