Transient boron diffusion in ion-implanted crystalline and amorphous silicon

Abstract

Boron diffusion in ion-implanted and annealed single-crystal and amorphized Si is compared to determine the effect of amorphization on the initial transient boron motion reported for single crystal. The boron was implanted at 20 keV and at doses of 1×1015 and 3×1015cm−2. The Si was either preamorphized or postamorphized to a depth of 320 nm by implantation of Si ions at three different energies. In the amorphized samples the entire boron profile was always contained within this distance. The samples were annealed by furnace or rapid thermal annealing to 900–1100 °C with or without a preanneal at 600 °C. The initial rapid diffusion transient in the tail region of the boron profile was observed in all the crystal samples. This transient was totally absent in the amorphized samples. This is manifest by careful comparison of boron concentration profiles determined by secondary ion mass spectrometry of single-crystal and amorphized samples after annealing. For anneals where significant motion occurs, the profiles of the amorphized samples could be fit with a computational model that did not include anomalous transient effects. It is proposed that excess interstitials cause the transient diffusion in the case of the crystalline samples. The source of interstitials is believed to be provided by the thermal dissolution of small clusters that are formed by the implantation process. They exist for only a short time, during which they enhance the boron diffusion. Since there is no enhanced diffusion in the amorphous region that regrows to single crystal, apparently interstitial clusters are neither produced by nor do they survive the regrowth process in that region. In addition, the interstitials generated by the damage beyond the amorphous-crystalline boundary are prevented from entering the regrown region by the dislocation loops formed at that boundary which act as a sink consuming the interstitials diffusing toward the surface.

Transient enhanced diffusion without {311} defects in low energy B+-implanted silicon

“…Others have reported similar results. 4 In order to understand the correlation of TED with defects arising from annealing following B ϩ damage, a number of studies have been conducted on the defect formation processes. [5][6][7][8][9][10] These studies have indicated that TED of B ϩ -implanted Si occurs by the pairing of B with Si self-interstitials.…”

A silicidation-induced process consideration for forming scale-down silicided junction

“…In addition, junction degradation at ST of 900 "C was present for the 750 and 900 "C activation, whereas no high-temperature deterioration was found for the 1000 "C activation. Previously, anomalous dopant diffusion was reported to occur during annealing due to interstitial defects [7]. Moreover, DLTS analyses of the silicided junctions indicated a deep level of about 0.6 eV which is close to the trap level of CO in Si.…”

Various effects of silicidation on shallow p/sup +/ junctions formed by BF/sub 2//sup +/ implantation into thin poly-Si films on Si substrates

“…3 shows the boron depth profiles for the ITP and the Ni/ITP samples, respectively, implanted at 25 keV and annealed at 700 C. The simultaneous silicidation and junction formation would considerably drive-in the boron dopant and cause excellent junction in the Si substrate. While annealing, the diffusion of boron would be enhanced due to Si interstitial [11]. And, silicidation would also enhance the dopant diffusion [9], [10].…”