Germanium Ion Implantation Research Articles

Amorphization of silicon by high dose germanium ion implantation with no external cooling mechanism

Si(100) wafers were implanted by using three different methods: single-energy Ge + ion implantation, double-energy Ge + and Ge 2+ ion implantation, and double-energy Si + and Ge + ion implantation. The single-energy implantations were performed at energies from 50 to 180 keV, over the range of 8.38 × 10 15 to 5.80 × 10 16 ions/cm 2. By keeping the ion beam power density below 0.09 W/cm 2, full surface amorphization could be achieved in the single-energy Ge + implanted samples. Also beam heating was suppressed during implantation, although the implanter had no external cooling. In addition, a two-step single-energy implant technique using sequentially high and low power densities was further developed in order to reduce implantation times. In order to locate the amorphous/crystalline (a/c) interfaces far away from the concentration peak positions of the implanted Ge + ions, the double-energy Ge + and Ge 2+, and Si + and Ge + implantations were carried out. Three Ge + implanted wafers were either pre-implanted with 180 keV Si + ions, or post-implanted with 360 keV Ge 2+ ions, respectively, in order to locate deeper a/c interfaces. Channelling effect measurements indicate that the double-energy Ge + and Ge 2+ implantation is a preferable technique for wilfully tailoring the amorphous depth and the Ge peak position.

RBS channeling spectroscopy of Ge implanted epitaxial Si1-xGex layers

Si1-xGex layers were formed through high-dose germanium ion implantation into (100)Si substrates. Two alternative implantation techniques along with that of the single-energy Ge+ implantation were separately adopted: the double-energy Si+ and Ge+ method, and the double-energy Ge+ and Ge++ method. The purpose of the both double-energy methods was to form deeper amorphous layers by using relatively low-dose Si+ or Ge++ ion bombardment while the SiGe alloy layers were created by high dose Ge+ ion implantations. Furthermore, all the amorphized samples were epitaxialy regrown by conventional furnace annealing at temperature of 525 to 600°C. RBS channeling spectroscopy was used for optimizing these implantation processes. Measurements confirm that the double-energy Ge+ and Ge++ method is optimum because of generating fewer residual defects. Additionally, the preliminary result on the regrowth properties of the double-energy Ge+ and Ge++ implanted SiGe layer is also presented.

Improved crystalline quality of Si1−xGex formed by low-temperature germanium ion implantation

Improvement of crystalline quality in Si1−xGex formed by germanium ion implantation has been found. End-of-range defects were drastically reduced in number by lowering the substrate temperature during implantation with doses on the order of 1016 cm−2. This improvement was confirmed by electrical characterization of p-n junctions formed in the SiGe layer as well as by transmission electron microscopy.

Characterization of SiGe/Si heterostructures formed by Ge+ and C+ implantation

Formation of SiGe/Si heterostructures by germanium ion implantation was investigated. A germanium-implanted layer was grown epitaxially in the solid phase by thermal annealing. Two kinds of crystalline defects were observed. One is a misfit dislocation, and the other is a residual dislocation caused by ion bombardment. The p-n junction formed in the SiGe layer has a leakage current three orders of magnitude larger than that of a pure Si p-n junction fabricated with an identical process except for the Ge+ implantation. Carbon doping in the SiGe layer improves its crystalline quality and the junction characteristics.

Enhanced elimination of implantation damage upon exceeding the solid solubility

SiGe/Si heterostructures have been fabricated using germanium ion implantation into silicon and subsequent solid phase epitaxy (SPE) growth. The damage removal and boron diffusion in the SiGe/Si heterostructures formed by high-dose Ge+ preamorphized and BF2+ implanted Si(0 0 1) during SPE growth have been investigated by double-crystal X-ray diffraction (DCXRD) and secondary ion mass spectrometry (SIMS). The results show that annealing at 600°C for 60 min can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. Most damage induced by Ge+ and BF2+ ion implantation have been removed after annealing at 950°C for 60 min and accompanied by Ge diffusion, a boron diffusion has taken place. When annealing temperature rose to 1050°C, Ge diffusion has been slight while B diffusion has been deeper into the Si substrate with a very good distribution. The X-ray diffraction (0 0 4) rocking curves from the samples annealed at 1050°C for 60 min display two SiGe peaks, which may be related to the B and Ge concentration profiles.

Optimization of the germanium preamorphization conditions for shallow-junction formation

Shallow p/sup +/-n and n/sup +/-p junctions were formed in germanium preamorphized Si substrates. Germanium implantation was carried out over the energy range of 50-125 keV and at doses from 3*10/sup 14/ to 1*10/sup 15/ cm/sup -2/. p/sup +/-n junctions were formed by 10-keV boron implantation at a dose of 1*10/sup 15/ cm/sup -2/. Arsenic was implanted at 50 keV at a dose of 5*10/sup 15/ cm/sup -2/ to form the n/sup +/-p junctions. Rapid thermal annealing was used for dopant activation and damage removal. Ge, B, and As distribution profiles were measured by secondary ion mass spectroscopy. Rutherford backscattering spectrometry was used to study the dependence of the amorphous layer formation on the energy and dose of germanium ion implantation. Cross-sectional transmission electron microscopy was used to study the residual defects formed due to preamorphization. Complete elimination of the residual end-of-range damage was achieved in samples preamorphized by 50-keV/1*10/sup 15/ cm/sup -2/ germanium implantation. Areal and peripheral leakage current densities of the junctions were studied as a function of germanium implantation parameters. The results show that high-quality p/sup +/-n and n/sup +/-p junctions can be formed in germanium preamorphized substrates if the preamorphization conditions are optimized. >

Elimination of end-of-range and mask edge lateral damage in Ge+ preamorphized, B+ implanted Si

The problems of residual extended defects due to end-of-range ion implantation damage and mask edge lateral damage have been solved in this study for shallow boron junctions preamorphized via germanium ion implantation. Defect elimination has been achieved by adjusting the germanium ion energy, dose, and annealing temperature and ambient to minimize the local interstitial point defect concentration and optimize the role of the free surface in defect annihilation. For the combination of shallow, low dose 40 or 60 keV/2×1014 cm−2 Ge+ and 8 keV/1×1015 cm−2 B+ implants, a defect-free structure was obtained following a 1050 °C, 10 s rapid thermal anneal (RTA) in a nonoxidizing Ar ambient. For these samples, boron profiles determined using secondary ion mass spectroscopy (SIMS) showed the junction depth to be approximately 0.17 μm at a background doping of 1×1017 cm−3 with a sheet resistance of 136 Ω/⧠.

5372. The effect of germanium ion implantation dose on the amorphization and recrystallization of polycrystalline silicon films: Y Komem and I W Hall,J Appl Phys,52 (11), 1981, 6655–6658

5372. The effect of germanium ion implantation dose on the amorphization and recrystallization of polycrystalline silicon films: Y Komem and I W Hall,J Appl Phys,52 (11), 1981, 6655–6658

The effect of germanium ion implantation dose on the amorphization and recrystallization of polycrystalline silicon films

Polycrystalline Si films have been amorphized by implantation with 130-KeV Ge ions and subsequently recrystallized by conventional heat treatment. It is found that, after amorphization with a low ion dose, recrystallization produces a structure which is morphologically similar to the original film. By contrast, after high Ge dose implantation, recrystallization proceeds dendritically. An initial rationale for this behavior is proposed in terms of the lattice disorder introduced by ion implantation.