Effect of plasma density on the distribution of incident ions and depth profile in plasma-based ion implanted layers

The retained dose and compositional depth profile were studied in the context of cylindrical target with different plasma density treated by plasma-based ion implantation (PBII). Nitrogen was implanted into silicon wafer clamped on the samples in order to acquire high quality profiles. Auger electron spectroscopy (AES) was used to acquire the nitrogen depth profile at the middle of Si wafer. A method, that combined fluid dynamic model to simulate plasma sheath expansion during high voltage pulse and TRIM code to simulate incident ion distribution in the solid was presented to simulate the experimental results. Both retained dose and N depth profile were compared with the results of theoretical simulation. The agreement between them for all three cases is good; that is, the model can give a good prediction and explanation to the experimental results. The retained dose for cylinder increases with increasing plasma density. The continuously distributed energy of incident ions and low N+/N2 ratio in the plasma shift the N depth profile nearer to the surface and reduce the range significantly.