| abstract |
Thin films are formed by formed by atomic layer deposition, whereby the composition of the film can be varied from monolayer to monolayer during alternating pulses of self-limiting chemistries. In an embodiment for producing ultrathin dielectrics, varying amounts of nitrogen are introduced during the cyclical process. A graded silicon oxynitride is thereby provided, even for extremely thin layers. The lower surface of the gate dielectric comprises silicon oxide, with excellent interface properties, which the upper surface of the gate dielectric has a high nitrogen content to aid in resisting boron diffusion from an overlying gate electrode. In an embodiment for lining dual damascene trenches and vias prior to filling, metal nitride (e.g., WN) is first formed as a barrier. During the cyclical process, self-limiting metal phases (that can be a different metal from that in the metal nitride) are introduced and gradually increase in frequency, mixing metal (e.g., Cu) with metal nitride (e.g., WN). Subsequent reduction of the frequency of the metal nitride phases results in a greater concentration of copper, until a pure metal seed region is left, and the trenches/vias can be filled by electroplating copper over this seed region. Advantageously, the graded compositions avoid such problems as etch rate control, electromigration and non-ohmic electrical contact that can occur at sharp material interfaces. |