C Implantation for Suppression of Dislocation Formation

Abstract

This paper will show that annealing of Si implanted with moderate doses of 725 keV B results in the formation of secondary defects, the so-called category I dislocations. Surprisingly, 12C, with roughly the same mass as 11B, behaves in a very different way. Carbon implant damage does not result in dislocation formation even for damage levels > 100 times higher than that required for B implants. C is also able to avoid dislocation formation of co-implanted B ions. The C-dose needed to avoid dislocation formation for the B implant increases nonlinearly with B-dose. Special C-related secondary defects remain after annealing if the C-dose is higher than 4×1015 /cm2.

Dislocation formation and B transient diffusion in C coimplanted Si

“…11,12 This effect is studied here as a function of the overlap between the C profile and the damage created by a 150 keV Si implant ͑for which the damage distribution peaks at about 0.2 m͒ performed to a dose of 3ϫ10 14 cm Ϫ2 . The C was implanted in three such samples to a dose of 3ϫ10 15 cm Ϫ2 , each with a different energy: 700 keV ͑R p Ϸ1.2 m͒, 170 keV ͑R p Ϸ0.4 m͒, and 70 keV ͑R p Ϸ0.2 m͒.…”

“…10 Moreover, dislocation formation is suppressed in B-and P-implanted Si if an additional C implantation is performed. 11,12 Some indications that the presence of C may reduce the transient diffusion of B have also been reported. 13 Also gettering of metallic impurities such as gold, 14 copper, 15 or iron 16 in C-implanted silicon has been observed.…”

“…Extensive modeling of the B TED at 900°C shows that the C-related damage is probably formed by coprecipitation of C and Si atoms in Si-C complexes which have a negative effect on the electrical properties of the implanted layer. These complexes have the approximate stoichiometry Si 1.15 C. Annealing treatment at higher temperatures partially dissolves the damage complexes, thus improving the electrical quality of the layer, but at the same time causing transient diffusion or dislocations even in the presence of C. 13 C, 11 B, and 28 Si implants into Si ͑100͒ were performed at room temperature, using a tilt angle of 7°from the surface normal to minimize channeling. Two different substrates were used: 0.23 ⍀ cm, p-type, float-zone ͑FZ͒ wafers and 40 ⍀ cm, p-type, Czochralski grown ͑CZ͒ wafers.…”

Physical mechanisms of transient enhanced dopant diffusion in ion-implanted silicon

“…Recently, it has been reported that C coimplantation can be used to reduce TED of B. 41,42 This reduction has been attributed [43][44][45] to the fact that the implanted C provides a sink for excess interstitials during annealing. The efficacy of C coimplantation in suppressing TED is limited by the fact that the C needs to getter its own interstitial damage in addition to the interstitials from the dopant implant.…”

“…The efficacy of C coimplantation in suppressing TED is limited by the fact that the C needs to getter its own interstitial damage in addition to the interstitials from the dopant implant. 44 It could therefore be more efficient to incorporate substitutional C in c-Si before implanting the dopant species, which is an additional subject of research in this article.…”