Study of Structure and Electrical Characteristics of Silicon Oxynitride Layers Synthesized by Dual Ion Implantation in Silicon and their Annealing Behaviour

Abstract

30 keV low-energy ion-implantor was used to synthesize silicon oxynitride (Si x O y N z ) insulating layers. The reactive ion-beams of molecular oxygen ( 16 O 2 + ) and nitrogen ( 14 N 2 + ) were co-implanted sequentially into silicon at room temperature in the ratio 1:1 to total fluence level ranging from 5x10 16 to 1x10 18 ions-cm -2 . Characterization of ion-beam synthesized Si x O y N z layers was carried out by X-ray diffraction (XRD) and current-voltage (I-V) measurements before and after rapid thermal annealing (RTA) treatments at different temperatures. XRD studies of the as implanted samples indicate formation of oxynitride layers with the presence of implanted oxygen mostly in the oxide phase and nitrogen in the dissolved form in the implanted silicon layer. RTA of the samples at higher temperature results in the transformation of oxide and nitride into new phases. Alion-beam synthesized oxynitride-Si (MIS) devices were fabricated with as implanted and annealed samples to study current density voltage (J-V) characteristics. These results show ohmic conduction at low voltages and non-ohmic behavior at higher fields. Results obtained in the present work show higher electrical resitivity and the lower trap density for the ion-beam synthesized oxynitride films than those films prepared by other methods.Introduction The low energy reactive ion-implantation in silicon at high fluence (≥ 10 16 ) ions-cm -2 levels can be used to produce new materials with compositions and structures unattainable by conventional techniques. The synthesis of surface layers of silicon oxynitride by reactive oxygen and nitrogen ion-implantation into silicon is technologically important for the device processes. The composition, structure and electrical properties of the silicon oxynitride layers are found to depend strongly on the method of preparation and annealing treatments. Thus, it is necessary to establish the structural properties of such films prepared by different techniques with desired electrical characteristics for semiconductor device applications. Some researchers have reported the structural and electrical properties of silicon oxynitride insulating films prepared by conventional techniques (1-6). However, only a few reports are available in the literature on silicon oxynitride surface layers synthesized by ion-beam techniques (7-9). From this brief survey, it is evident that the structure and electrical characteristics of ion beam synthesized oxynitride has scope of further investigation. Earlier, we have reported FTIR [Fourier Transform Infrared] (10,11) structural properties and ESR [Electron Spin Resonance] (12) defects of silicon oxynitride (Si x O y N z ) layers synthesized by high fluence reactive ion implantation into silicon ranging from 5x10 16 to 1x10 18 ions-cm -2 at 30keV. The present work aims to understand the formation of silicon oxide-nitride phases in oxygen-nitrogen co-implanted silicon following RTA (Rapid Thermal Annealing) in N 2 atmosphere by X-ray diffraction studies and its electrical charact...