The formation of ultrathin (≤20 nm) and smooth CoSi2 layers on c–Si substrates has been studied by using a one- and a two-step RTP silicidation method. Pinhole-free silicide layers with a thickness down to ∼10–12 nm were formed on n−, n+, and p+ crystalline Si substrates in the one-step RTP process by sputtering of Co films as thin as 4 nm and subsequent silicidation at 750 °C for 5 or 30 s. The two-step RTP silicidation method is based on the consumption of only a small fraction of a thick sputtered Co film to form Co2Si or CoSi during a first RTP step at 400–500 °C. A selective etch follows to remove the unreacted Co film. During a second, higher temperature, RTP step CoSi2 is formed. Pinhole-free and smooth CoSi2 films with a thickness down to 20 nm were formed in this way on both n+ and p+ monocrystalline Si substrates.

Channeled implants have been performed with lOOkeV 28Si+ into p-type Si(100) to obtain a buried amorphous layer. Before and after recrystallization of the a-Si layer, Cu was implanted at an energy of 15 keV and a dose ranging from 5E13 to 1E15 I cm2- to obtain a high concentration of Cu in the near surface region. Also, Cu implants were performed into virgin Si for comparison. After Cu implantation, thermal annealing was performed at temperatures between 490 °C and 900 °C for 10 min. to 320 min. Cu profiles before and after annealing were studied with Rutherford Backscattering Spectrometry and channeling analysis. For the case where Cu was implanted after recrystallization of the buried amorphous layer, Cu was gettered at the position where the ale interfaces met during recrystallization. For the case where Cu was implanted before recrystallization, Cu diffused towards the buried a-Si region upon annealing and was trapped inside the recrystallizing buried amorphous layer. The results show that buried damage layers can effectively getter Cufrom the Si surface layer and gettering is most efficient at 600 °C.

The diffusion of boron ions implanted in Si(100) during high temperature treatment has been studied by means of Secondary Ion Mass Spectrometry. The boron ions were implanted at energies of 5 and 10 keV along random direction and along [100]. The implantation dose amounted to 1×1013/cm2. During annealing an enhanced diffusion of boron is observed in the tail region of the implantation profiles. In all cases the enhanced diffusion is completed after Rapid Thermal Annealing at 900°Cfor 10”. The enhanced diffusion is largest for the channeled ion implantations. Channeling analysis shows that the transient diffusion is not correlated with the annihilation of defects near the projected range. Therefore, the observed diffusion tail is attributed to rapidly diffusing interstitial boron. Post-amorphization of boron implanted silicon with Si+ ions is used to prevent transient diffusion. Thus a very sharp pn-junction is obtained at a depth of 03 jim and the effective number of charge carriers equals the implanted dose after annealing at 550°Cfor 5hrs and 1000°Cfor 10”.