A Study of Boron Clustering Transients and Mechanisms in Doped Silicon
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A Study of Boron Clustering Transients and Mechanisms in Doped Silicon Aaron D. Lilak, Viswanath Krishnamoorthy, David Vieira, Mark Law, and Kevin Jones; SWAMP Center; University of Florida.
Abstract The ion implantation of boron remains the most practical means o forming shallow and ultra-shallow p+/n junctions in silicon. A highl conductive junction requires both a large density of dopant atoms and electrical activation amongst these. While it is possible to simply higher doses of boron at lower energies, the potential benefits of th changes are often muted by the electrical deactivation of the boron w occurs through a clustering process. Therefore, it is important to d understanding of the kinetics and transients involved in these proces It has been shown that ion implanted boron clusters with interst residual from the implantation process. These clusters are immobile, fractionally or totally electrically inactive, and very thermally sta study a series of experiments were conducted in order to investigate processes. In addition to this, a means of utilizing X-ray Diffractio to correlate electrical activity to the rocking curve has been develo Experimental A series of boron implants (20keV to 80keV) were performed at 2* dose into n-type (~100 ohm-cm) silicon wafers. These samples we subjected to a 7400C 40min anneal, a condition known to be highly fav 1,2. to BIC formation The boron in these BIC complexes was then activated/reactivated through a second bounce anneal. The degree of electrical activation was monitored during these anneals by spreading resistance profilometry and later correlated to the X-ray diffraction curve. 0C 740 Immediately following the 40min anneal, a large fraction of the 14 boron was deactivated. For the case of the 20keV boron 2*10 implant a net activation of 25% was determined following the 7400C 40 minute anneal shown in Figure 1. Figure 2 shows the electrical activation of this 14 cm-2 boron implant clustered with a 7400C 40 minute anneal 20keV 2*10 and later partially reactivated to 47% electrical activity with a 850 minute anneal. cm -2
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Figure 2: Electrical activation exhibited by the same 20keV 2e14cm-2 sample clustered by a 7400C 40 minute anneal as shown in Figure 1 following reactivation by a 8500C 30 minute anneal. The net activation of this sample is 47% compared to the 25% exhibited by the sample following the 740C 40 minute anneal.
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Figure 3: Fractional activation as a function of implant energy and anneal sequence.
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