Influence of a RF plasma on the nucleation of aluminium using n-trimethy lamine-alane -TMAA- as precursor

Aluminium films deposited on silicon with MOCVD methods generally exihibit a high surface roughness due to the hindered nucleation. To decrease the nucleation barrier a pretreatment of the wafer with TiClsub4 vapor as a chemical activator is commonly suggested. This work examines the influence of a rf hydrogen plasma on the nucleation of aluminium on Si and SiOsub2 using TMAA as precursor. Atomic force microscopy (AFM) was used to determine the surface roughnesses and crystallite sizes of the aluminum deposits. Without plasma activation the nucleation barrier on. Si (111) is substantially higher than on oxidized Si and therefore the pretreatment of the wafer plays an important role. The hydrogen plasma causes a substantial increase of the nucleus density leading to deposits with lower surface roughnesses compared to conventional MOCVD aluminium. The influence of the substrate on the nucleation is almost "switched off" by the plasma activation and the grain sizes of Al on Si (111) and S i0sub2 differ only slightly. Relatively smooth films with a resistivity of 2.7 MyOmegacm are obtainable by employing a plasma activated nucleation step followed by a thermal MOCVD process. The increased nucleation rate is discussed in terms of kinetic effects of plasma activation.