The influence of boron ion implantation on hydrogen blister formation in n-type silicon

We have studied the formation of surface blisters in < 100 > n-type silicon following co-implantation with boron and hydrogen. The silicon substrates had four different n-type dopant levels, ranging from 10(14) to 10(19) cm(- 3). These substrates were implanted with 240 keV B+ ions to a dose of 10(15 ) cm(-2), followed by a rapid thermal anneal at 900 degrees C for 30-60 s t o force the boron atoms into substitutional lattice positions (activation). The samples were then implanted with 40 keV H+ to a dose of 5 x 10(16) cm( -2). The implanted H+ distribution peaks at a depth of about 475 nm, wherea s the distribution in the implanted B+ is broader and peaks at about 705 nm . To evaluate the role of the B+ implantation, control samples were prepare d by implanting with H+ only. Following the H+ implantation, all the sample s were vacuum annealed at 390 degrees C for 10 min. Blisters resulting from subsurface cracking at depths of about 400 nm, were observed in most of th e B+ implanted samples, but not in the samples implanted with H+ only. This study indicates that the blistering results from the coalescence of implan ted H into bubbles. The doping with B facilitates the short-range migration of the H interstitials and the formation of bubbles. A comparison of the o bserved crack depth with the depth of the damage peak resulting from the H implantation (evaluated by the computer code TRIM) suggests that the nucle ation of H bubbles occurs at the regions of maximum radiation damage, and n ot at the regions of maximum H concentration. For given values of B+ and H doping, the blister density was found to decrease with increasing n-type d oping, when the boron is activated. Blister formation was also observed in B+ implanted samples which had not been activated. In this case, the bliste r density was found to increase with increasing value of n-type doping. (C) 1999 American Institute of Physics. [S0021-8979(99)02820-0].