Cavities and dislocations induced in silicon by MeV He implantation

We implanted n-type silicon with 1.6 MeV helium at fluences ranging from 1 x 10(16) to 1 x 10(17) He/cm(2) while keeping a constant dose rate. These s amples were then subjected to 800 degrees C annealing for 30 min. The resul ts obtained by means of cross-sectional transmission electron microscopy in dicate that the density of cavities is fluence dependent with homogeneous d istribution of cavity sizes when fluences of 5 x 10(16) and 10(17) He/cm(2) are used. The threshold fluence required to form cavities is found to be b etween 1 and 2 x 10(16) He/cm(2). For the 2 x 10(16) He/cm(2) dose, we obse rved loop punching induced by a concerted action of overpressurized bubbles , whereas He implants at doses of 5 x 10(16) and 1 x 10(17)/cm(2) lead to t he formation of {311} defects. At the same time, non Rutherford elastic bac kscattering (NREBS) experiments using 2.5 MeV H+ provide the fraction of he lium remaining in cavities after different annealing times at 800 degrees C . The NREBS data show a fast He release process for short annealing times ( < 2000 s). Then, the He amount decreases slowly and after 30 000 s about 40 % of the helium still remain in cavities. Finally, an additional implantati on with 50 keV He at 5 x 10(16) He/cm(2) shows the difference in cavity siz e distribution between MeV and keV implantation. (C) 2000 American Institut e of Physics. [S0021-8979(00)02304-5].