Dopant Activation and Epitaxial Regrowth in P-Implanted Pseudomorphic Ge 0.12 Si 0.88 Layers On Si(100)
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"**University of California, Los Angeles, CA 90024
***D. N. Theodore, Motorola Inc., Mesa, Arizona, AZ 85202
Abstract
A pseudomorphic Ge0 .12 Si0 .88 film 265 nm thick grown on a Si(100) substrate by molecular beam epitaxy was implanted at room temperature with a dose of 1.5 x 1015 cm2 of 100 keV P ions. The projected range of the ions is about 125 nm, which is well within the film thickness. Only the top portion of the Ge 0 . 12 Si 0 .88 layer was amorphized by the implantation. Both implanted and non-implanted samples were subsequently annealed in vacuum for 30 minutes from 400 IC to 800 'C. Values of electron Hall sheet mobility and concentration in the implanted Ge 0 . 12 Si0. 88 epilayer were measured after annealing. The solid phase epitaxial regrowth is complete at 550 'C, where the implanted phosphorus reaches - 100 % activation. The regrown Ge0 .12 Si0 .88 layer exhibits inferior crystalline quality to that of the virgin sample and is relaxed, but the non-implanted portion of the film remains pseudomorphic at 550 'C . When annealed at 800 'C, the strain in the whole epilayer relaxes. The sheet electron mobility values measured at room temperature in the regrown samples (Tann > 550 °C) are about 20% less than those of pure Si.
Introduction SiIGexSil-x heterostructures are attractive for high performance electronic and optical devices and circuits, since it is a silicon-based technology that can be utilized to adjust bandgaps and enhance carrier mobility for the improvement of designs. Numerous SiIGexSi I_x devices have been made, and the fabrication of many of them requires the use of ion implantation. Recent studies revealed that the implantation-induced damage and the subsequent annealing behavior of Si/GexSilx heterostructures are different from those of Si. It is therefore important to study how to properly apply ion implantation to Si/GexSilix. For example, to achieve best dopant activation and minimize the residual damage generated by energetic ions, in Si IC processing one usually amorphizes the doped region first and subsequently anneals it to let epitaxial regrowth take place. However, it was reported that for strained GexSi I-x layers irradiated by Si ions, the regrowth results in poor crystalline quality [ 1-4]. Even though there are several studies on the solid-phase epitaxial regrowth for GexSi 1-x layers [5-8], studies of dopant incorporation and their activation which take advantage of this regrowth in strained GexSil-x layers have only been reported by Atzmon et al [9-10] and Hong et al [11] where Sb ions where used. In this paper, we study the implantation of the practically useful P ions. We use 100 keV 3 1p ions to amorphize a pseudomorphic Ge0 . 12 Si0 . 88 layer without damaging the Si-GeSi interface. This layer is later annealed in vacuum at various
485 Mat. Res. Soc. Symp. Proc. Vol. 321. 6,1994 Materials Research Society
temperatures. The focus of this study is on the electrical and material characterization and the stability of the heterostructure after ion implantation and a
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