خصوصيات ساختاري و اپتيكي فيلم نيتريد سيليكو ن توليد شده بر رو ي سيليكون توسط فرآيند كاشت يون با انرژي كم

Structural and optical properties of silicon nitride film generated on Si substrate by low energy ion implantation

Introduction: Doping technology is one of the vital silicon (Si) processing technologies to fabricate semiconductor devices and to control the electrical characteristics of such devices. In recent years more attention has been paid to nitrides. Some binary nitrides, such as Si3N4, AlN and GaN, have been intensively investigated both experimentally and theoretically and are applied in industry. Within these binary nitrides, the combination of the electronic and the mechanical properties of Si3N4 make it the extremely attractive material for a wide variety of potential applications in semiconductor industry. Aim: In this work the surface of Si wafers is bombarded with nitrogen ions at various ion beam fluency and the results are investigated. Crystalline structure, topology of surface, electrical and optical properties is studied in order to investigate the effect of doping in physical properties of silicon. The goal of our present work is to achieve a better understanding of the processes that occur during the thin film growth of Si3N4 caused by the nitrogen ion and Si surface reaction. Materials and Methods: Single crystal p-type silicon wafers of 1*1 cm with < 4 0 0> orientation and 0.509 mm thickness at 6.87 ^.cm resistivity and 135.7 Q/^ sheet resistivity is used as the substrate material. In this experiment, applied nitrogen ion beam of 29 keV energy at 100 DA/cm2 ion current density hit the targets at the ion fluency varying from 1016 to 1018 ions per cm2. A vacuum of about 4*10-3 pa is maintained in the target chamber and the temperature of the samples reach to about 41 to 410 K (depend on the ion beam dose) during the implantation. Transition and reflection spectrum, AFM micrographs, X-Ray diffraction pattern, and four point resistivity probe are used to characterize the implanted samples. Results: Results from XRD pattern confirm that in this range of ion beam energy, the processes of implantation changes the lattice constant so on the cubic lattice of silicon the orthorhombic lattice of Si3N4 is formed. Increasing the dose of ion beam increases the RMS roughness of the surface. Sheet resistivity of implanted samples is noticeably affected by the implantation processes and increases about 50%. Nitrogen ion beam implantation generates defect levels in silicon and changes the energy of band gap. This energy is calculated to be 1.098±1 eV which is 0.018 eV greater than the band gap energy of silicon substrate.