Diffusion of ion implanted boron in preamorphized silicon

Abstract

Transient enhanced diffusion of boron in preamorphized and subsequently regrown Si was studied by secondary ion mass spectrometry SIMS and transmission electron microscopy TEM. A comparison of 4 keV, 1 10 14 /cm 2 boron implants into crystalline and Ge preamorphized silicon was undertaken. Upon annealing the B implant into crystalline material exhibited the well-known transient enhanced diffusion TED. In this case the peak of the boron distribution was relatively immobile and only B in the tail showed TED. In the second set of samples, the surface was first preamorphized by a 180 keV, 110 15 /cm 2 Ge implant which produced an amorphous layer 2300 Å deep, which then was implanted with boron. After implantation the tail of the B distribution extended to only 700 Å. Upon annealing, TED of the boron in the regrown Si was also observed, but the diffusion profile was very different. In this case the peak showed no clustering, so the entire profile diffused. The time for the TED to decay was around 15 min at 800°C. TEM results indicate that the 311 defects in the end of range damage finish dissolving between 10 and 60 min at 800°C. These results indicate that for these Ge preamorphization conditions, not only do the end of range defects not block the flow of interstitials into the regrown silicon, the 311 defects in the end of range damage act as the source of interstitials. In addition, boron does not appear to cluster in regrown silicon.

Fluorine incorporation in preamorphized silicon

“…[13][14][15] The results reported in this article could have important implications for the use of fluorine in the realization of future generation devices. The preamorphization implant leaves a damage band, rich in Is, just beyond the original amorphous-crystalline ͑a-c͒ interface.…”

Modeling of B diffusion in the presence of Ge

“…Another consequence of deep pre-amorphization is the reduced formation of BICs, as previous experiments showed that BICs do not form in preamorphized, and then regrown layers. 13,14 It should also be noted that secondary Ge effects, such as band gap narrowing and strain, are expected to be minimal. Band gap difference at the Ge profile peak concentration of ϳ1.5ϫ 10 21 cm −3 should not exceed 15 meV at room temperature, after Weber and Alonso.…”

Annealing kinetics of {311} defects and dislocation loops in the end-of-range damage region of ion implanted silicon

“…Other authors have observed that in the EOR, at short times at moderate temperatures, there is initially a large number of ͕311͖ defects and a smaller number of dislocation loops. [10][11][12] With the progression of annealing to longer times, the number of ͕311͖ defects decreases and the number of dislocation loops increases. At longer times and higher temperatures, ͕311͖ defects disappear and only dislocation loops remain.…”