Paper EM+TF-MoM10
In Situ Infrared Study on the Interfacial Layer Formation during the Atomic Layer Deposition of Aluminum Silicate on Chemically-treated InP(100)

Monday, October 28, 2013, 11:20 am, Room 101 B

Growing suitable high-k dielectrics for high-performance III-V metal-oxide semiconductor field effect transistor (MOSFET) devices remains a challenge because native oxides on III-V semiconductors contain a high number of interfacial defects. In particular, atomic layer deposition (ALD) of Al₂O₃ has been thoroughly studied, featuring a “self-cleaning” phenomenon or reduction process of the initial native oxide by trimethyl aluminum. Despite notable progress in improving the interface quality, the number of interfacial defects still prevents the manufacturing of quality MOSFET devices. A fundamental understanding of the chemical composition of the interface and its evolution during processing is important to make further progress. In this study, in-situ infrared (IR) spectroscopy is used to examine the growth at 300°C of aluminum silicate (AlSiO_x) using trimethylaluminum (TMA), silicon tetrachloride (SiCl₄) and heavy water (D₂O) on degreased native oxides and chemically-treated (5% vol. HF and 10% vol. (NH₄)₂S) InP(100) surfaces. After an initial TMA exposure, the formation of Al-O-P species is observed, with a loss of In(PO₃)₃ and gain of x-(PO₄) (x= In and Al) (at 1007 and 1145 cm^-1, respectively) along with the formation of Al-O-Al bonds (absorption band at 800 cm^-1). This observation is consistent with the “self-cleaning” effect whereby the native oxides are reduced by formation of aluminum oxide and different chemical species. Upon the subsequent D₂O exposure, the loss of the 1217 cm^-1 and 2942 cm^-1 bands indicates the removal of the aluminum-bound methyl groups through ligand exchange. Interestingly, a subsequent pulse of SiCl₄ gives rise to a vibrational mode at 1060 cm^-1, assigned to Si-O-P. This indicates that SiCl₄molecules primarily react surface P-O(D) groups to form a silicon phosphate structure on the native oxides. After the subsequent D₂O exposure, further growth of the mode at 1060 cm^-1 suggests the continued formation of surface Si-O-P. The presence of AlSiO_x is observed on the degreased native oxide InP(100) substrates after eight supercycles. In conclusion, a complex consisting of primarily of Al-O-P develops initially, associated with a self-cleaning mechanism. As further growth develops, a complex of Al-O-Si becomes apparent, as indicated by the appearance and growth of the mode at 1151 cm^-1. The information derived from this study makes it possible to optimize the growth conditions for tailored aluminum silicate layers on InP surfaces. This work is made possible by National Science Foundation as a part of the U.S. –Ireland R&D Partnership (Grant no. NSF-ECCS-0925844) and Science Foundation Ireland [Grant No.09/IN.1/I2633.]