A study of 2 MeV oxygen implantation to form deeply buried SiO 2 layers
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C. d'Anterroches and A. Golanski Centre National d'Etudes des Telecommunications, B.P. 98, F-38243 Meylan, France (Received 23 February 1989; accepted 18 May 1989) Oxygen ions were implanted into (100) oriented single crystal Si at energies in the range of 0.6 to 2 MeV at normal and oblique (60°) incidences. Oxygen concentration profiles were measured using the 16O(d, a)14N nuclear reaction for 900 keV deuterons. The experimentally measured oxygen distributions were subsequently fitted to the theoretical profiles calculated assuming the Pearson VI distribution. The distribution moments (Rp, Ai?p, ARL, skewness, and kurtosis) were deduced as the best fit parameters and compared to the computer simulation results (TRIM 87 and PRAL). Whatever the calculation method, the measured Rp and ARp values are close to those predicted by the theory. Deeply buried SiO2 layers were formed using a single step implantation and annealing process. A dose of 1.8 x 1018/cm2 of 2 MeV O + was implanted into the Si substrate maintained at a temperature of 550 °C. The implanted samples were characterized using the Rutherford backscattering (RBS)/channeling technique and cross-sectional transmission electron microscopy (XTEM). The implanted samples were subsequently annealed at 1350 °C for 4 h in an Ar ambient. The annealing process results in creating a continuous SiO2 layer 0.4 jum thick below a 1.6 ^m thick top single crystal silicon overlayer. The buried SiO2 layer contains the well-known faceted Si inclusions. The density of dislocations within the top Si layer remains lower than the XTEM detection limit of 107/cm2. Between the Si overlayer and the buried SiO2 a layer of faceted longitudinal SiO2 precipitates is present. A localized dislocation network links the precipitates to the buried SiO2 layer.
I. INTRODUCTION The very high quality, low dislocation density SOI (silicon on insulator) structures may be obtained via high dose implantation of oxygen at intermediate energies (150300 keV) followed by an appropriate high-temperature annealing.1"4 The resulting device-worthy SOI material called SIMOX (Separation by IMplantation of OXygen) is attractive for high-speed complementary metal-oxide-semiconductor (CMOS) circuits and radiation-hardened devices. As the quality of the material is essential for the device performance, the main challenge during the last few years has been oriented toward improvement in the quality of the top Si layer. Although the SIMOX material fabrication is conceptually simple, the relationship between the implantation and high temperature annealing parameters and the quality of the material in its final state appears to be complex and has not yet been fully understood. It has been well established, however, that the quality of the SIMOX material is strongly related to the implantation conditions and the resulting morphology in the as-implanted state.5"8 Because of the very nature of the SIMOX technique (high implanted oxygen doses and high temperature treatments), the threading dislocations generated during SiO
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