Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
Flash-lamp processing with millisecond pulses for ultra-shallow boron implants in silicon
Gebel, T.; Voelskow, M.; Eichhorn, F.; Skorupa, W.; Mannino, G.; Privitera, V.; Priolo, F.; Napolitani, E.; Carnera, A.
Higher integration in semiconductor technology causes the need for ultra-shallow junctions. Novel techniques are necessary to achieve abrupt and sharp profiles of dopants at high activation levels without significant diffusion of dopants. Because common RTP techniques are limited in temperature ramping speed, alternative methods for ultra-short time annealing are of great interest. In this paper we report on recent results from flash lamp annealing (FLA). Si (100) wafers were implanted with 500eV B+ ions to a fluence of 1015 cm-2. FLA was carried out at temperatures in the range 1100-1200°C with a soak time of 2-20ms using a bank of xenon flash-lamps. With this technique the final temperature is reached within one millisecond. Preheating of the samples from the rear side was performed at 250, 500 and 750°C by a bank of halogen lamps. For comparison conventional RTP was performed at 1100°C and 1200°C for the shortest reliable time of 1s and longer times up to 80 s. The boron diffusion and the dopant activation were investigated by secondary ion mass spectroscopy (SIMS) and spreading resistance profiling (SRP). The activated doses after FLA were as high as 20% of the implanted dose confined in a layer of only 60nm. The mechanical deformation induced to the samples due to the heat shock was investigated with X-ray reflection. The intensity of the specularly reflected beam (CuK radiation, scattering angle = 0.8°) is detected as a function of the incidence angle. The profile width and the distances between possible subsidiary peaks give integral values of the surface waveness.
Keywords: flash lamp annealing; ultra shallow junctions; RTP
Ion Implantation Technology, IIT 2002 September 22-27, 2002, Taos, New Mexico, USA