In situ X-ray photoelectron spectroscopy analysis of the atomic layer deposition of Al 2 O 3 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 an in situ X-ray photoelectron spectroscopy technique to study the ALD growth of Al 2 O 3 , from trimethylaluminum and H 2 O, on the SiO x /Si surface. We find that an electric dipole is formed at the Al 2 O 3 /SiO x interface immediately after the first Al 2 O 3 layer is deposited. We also observe persistent surface methyl groups in the H 2 O half-cycle during ALD, and the amount of the persistent methyls is particularly higher during the initial Al 2 O 3 ALD growth, which suggests the formation of Si-CH 3 on the surface. These findings can provide useful routes and insights toward interface engineering by ALD.