In situ x-ray photoelectron spectroscopy analysis of the atomic layer deposition of Al2O3 on SiO x /Si: Interface dipole and persistent surface groups

Atomic layer deposition (ALD) has become an essential technology in many areas. To better develop and use this technology, it is of the pivot to understand the surface chemistry during the ALD film growth. The growth of an ALD oxide film may also induce an electric dipole at the interface, which may be further tuned to modulate the flat band voltage for electronic device applications. To understand the associated surface chemistry and interface dipole formation process, we herein employ anin situx-ray photoelectron spectroscopy technique to study the ALD growth of Al₂O₃, from trimethylaluminum and H₂O, on the SiO_x/Si surface. We find that an electric dipole is formed at the Al₂O₃/SiO_xinterface immediately after the first Al₂O₃layer is deposited. We also observe persistent surface methyl groups in the H₂O half-cycle during ALD, and the amount of the persistent methyls is particularly higher during the initial Al₂O₃ALD growth, which suggests the formation of Si-CH₃on the surface. These findings can provide useful routes and insights toward interface engineering by ALD.