The distribution of condensed defect structures formed in annealed boron-implanted silicon

Abstract

Silicon has been implanted with between 10 14 and 10 16 boron ions/cm 2 at energies of 25, 50, 75 and 100 keV; it has also been annealed at temperatures of between 873 and 1073 °K when the implanted boron ions occupy substitutional sites and form a ‘doped’ surface layer in which the doping profile can be accurately controlled, a desirable property in the manufacture of solid state circuits and devices (Large & Bicknell 1967). The implanted layers have been examined by both electron microscopy and electron diffraction before, during and after annealing to study the changes in crystal structures involved. For transmission electron microscope studies the silicon must be thinned to provide areas less than 1 p m in thickness, otherwise the electron beam is entirely absorbed within the specimen. It has been found that a modified form of jet etching using a turbulent jet enables large areas suitable for transmission electron microscopy to be easily produced from all types of specimens, both annealed and unannealed. Although specimens have been prepared and implanted with boron ions of different energies and doses the results discussed, which are typical of the range covered, are those obtained from silicon implanted with single energy 50 keV boron ions with a dose of 2 x 10 15 ions/cm 2 .