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Low-energy high-flux ion bombardment-induced interfacial mixing during Al2O3 plasma-enhanced atomic layer deposition

We investigated the formation mechanism of interfacially mixed AlSiOx films on Si surfaces under low-energy ( 4 × 1015 cm−2 s−1) O2+ ion bombardment during Al2O3 plasma-enhanced atomic layer deposition. When high-dose O2+ ions (>1 × 1017 cm−2 cycle−1) were incident on the growing film surface during the oxidation steps in Al2O3 atomic layer deposition (ALD), interfacially mixed films with thin (∼0.8 nm) SiOx interlayers were formed on Si surfaces. The deposited films possessed a layered structure of Al2O3/AlSiOx/AlOx layers. In order to reveal the formation mechanism, films deposited during the early stages of ALD were evaluated using an angle-resolved x-ray photoelectron spectroscope. In the first oxidation step, thin, low-density SiOx films with weak Si–O bonds containing excess oxygen were formed on the Si surface. In subsequent oxidation steps, adsorbed Al atoms on the surface were knocked on by the energetic ions and penetrated into the SiOx film. As a result, Al atoms were taken into SiOx. Some of the Al atoms accumulated near the interface. After several tens of cycles, ordinary Al2O3 films were deposited on the Si-rich layers. Thus, the films with a layered structure of Al2O3/AlSiOx/AlOx layers were formed on the Si substrate.