Cavities in helium implanted and annealed silicon characterized by spectroscopic ellipsometry

The formation of helium induced cavities in silicon during short-time annea ling is analyzed by spectroscopic ellipsometry. Specimens implanted with 40 keV He+ ions to a dose of 5x10(16) cm(-2) are heat treated at 800 degrees C for times of 1-1200 s by rapid thermal annealing. Spectroscopic ellipsome try is employed to obtain quantitative information on the cavity volume dep th profiles. A newly developed formula is used to model the optical multila yer depth profiles. The cavity volume is found to increase during annealing for about 300 s and to decrease for longer annealing times. Over this char acteristic time a marked change in the He loss occurs, which has been repor ted only recently. Swelling of the helium implanted and annealed silicon is analyzed using an atomic force microscope. Step heights are consistent wit h the cavity volume per unit area obtained from spectroscopic ellipsometry data analysis. The number density of cavities after annealing for 600 s is calculated to be approximate to 1.16 +/- 0.27x10(17) cm(-3) and is found to be largely independent of depth in the central part of the cavity layer. ( C) 1999 American Institute of Physics. [S0021-8979(99)05420-1].