Stability studies of ultrashallow junction formed by low energy boron implant and spike annealing

The stability of junctions formed by spike anneal remains a crucial issue for the device performance. In this study, 0.2 keV B implanted silicon was thermally spike annealed at 1100°C. Samples were then furnace annealed under temperatures between 550 and 750°C to study their stabilities. We have observed the anomalous diffusion of boron during the post-spike furnace annealing in nitrogen ambient. The anomalous behavior shows two features in the near-surface region and in the tail region. B diffusion in the tail region was transient, e.g., with an enhancement of 10 ³×equilibrium at 700°C for the first 60 s. In the near-surface region, a large number of B atoms move toward the native oxide/Si interface with a diffusion rate also transient and similar to that observed in the tail region. It is indicated that interstitials are generated due to spike annealing and will cause instability of the junction during the following thermal processes.