| AVS 54th International Symposium | |
| Thin Film | Tuesday Sessions |
| Session TF-TuA |
| Session: | Surface Chemistry for Atomic Layer Deposition |
| Presenter: | K.J. Choi, University of Texas at Dallas |
| Authors: | K.J. Choi, University of Texas at Dallas S.J. McDonnell, Dublin City University, Ireland R.M. Wallace, University of Texas at Dallas J. Kim, University of Texas at Dallas |
| Correspondent: | Click to Email |
In atomic layer deposition (ALD) of Al2O3 on H-terminated silicon substrates, it is often observed that the initial growth rate of Al2O3 films is much slower than that in the steady-state condition after several cycles. This phenomenon is frequently called an incubation period, which has been extensively investigated by using various in-situ surface characterization methods, such as quartz crystal microbalance, quadrupole mass spectroscopy, FT-IR etc. Although X-ray photoelectron spectroscopy (XPS) provides useful chemical binding information at the surface, a relatively few papers have been published regarding in-situ XPS investigations possibly due to a ultra-high vacuum (UHV) requirement which is not easily compatible to ALD system. In this study, in-situ XPS is used to investigate on chemical binding status during formation of Al2O3 thin films on an HF-last Si wafer. All experiments were carried out in an UHV system consisting of various deposition tools, including atomic layer deposition, sputter deposition, molecular beam epitaxy/deposition, and e-beam evaporation, as well as surface characterization methods including XPS, UPS, STM and AFM. The Al2O3 film was grown at 300oC on HF-last Si substrate using trimethylalumium [Al(CH3)3, TMA] as the aluminum precursor and H2O as the oxidizing agent. A cycle of the deposition process consisted of 0.1 s of TMA pulse, 10 s of N2 purge, 0.1 s of H2O pulse and 10 s of N2 purge. The growth rate is about 0.11nm/cycle. XPS analysis was conducted on Al2O3 thin films resulting from a 3-cycle deposition. The Al2O3 thin films were grown in half cycle steps (TMA pulse+N2 purge or H2O pulse + N2 purge) and analyzed in-situ so that the initial growth of Al2O3 could be observed. The Al2P3/2 photoelectron emission peak appears after the 1 cycle + TMA pulse + N2 purge. As the number of cycles is increased, the peak intensity of Al2P3/2 increases in TMA pulse + N2 purge step, and does not increase in H2O pulse + N2 purge step. In addition, we will also present in-situ vs. ex-situ XPS analysis of ALD Al2O3 in this presentation.