Synthesis of buried silicon oxynitride layers by ion implantation for silicon-on-insulator (SOI) structures (original) (raw)
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Synthesis of silicon oxynitride layers by dual ion-implantation and their annealing behaviour
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2003
Single crystal n-type silicon samples were implanted at room temperature sequentially by molecular oxygen ( 16O 2+) and nitrogen ( 14N 2+) in different proportions to high fluence levels ranging from 5 × 10 16 to 1 × 10 18 ions cm -2 to synthesize silicon oxynitride layers of various compositions. Rapid thermal annealing (RTA) of some samples was carried out at different temperatures in nitrogen ambient. Fourier transform infrared (FTIR) measurements were performed on as-implanted and on annealed samples. The FTIR studies show that the structure of ion-beam synthesized oxynitride layers are strongly dependent on total ion-fluence as well as on the ratio of implanted oxygen and nitrogen. The Si xO yN z structures formed at lower fluence levels are homogeneous, at intermediate fluence levels are composed of separate phases of oxide, nitride and some complexes of O, N and Si and at higher fluence levels seem to have again homogeneous silicon oxynitride complex structures (Si xO yN z) due to sputter limited profile of implanted ions. RTA studies show pronounced structural changes of the ion-beam synthesized layers on heat treatment at different temperatures. The spectra of annealed samples showed shift of the peak towards higher wave number. The ESR signal of silicon samples implanted to different fluence levels exhibited an isotropic g-value of 2.0045 corresponding to D-center with line width 8 G. The spin density was found to decrease with increase in ion-fluence.
Vacuum, 2009
Silicon oxynitride (Si x O y N z ) buried insulating layers were synthesized by implantation of nitrogen ( 14 N þ ) and oxygen ( 16 O þ ) ions sequentially in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 Â 10 17 to 5 Â 10 17 cm À2 to prepare silicon on insulator (SOI) structures. The as implanted samples were held at 270 C and irradiated to total fluence of 1 Â 10 14 cm À2 by 60 MeV Ni þ5 to study the structural changes/ recrystallization of SOI structures induced by swift heavy ion (SHI) irradiation. Fourier transform infrared (FTIR) measurements on the as implanted samples ( 1 Â 10 18 cm À2 ) show a single absorption band in the wavenumber range 1300-750 cm À1 attributed to the formation of silicon oxynitride (Si-O-N) bonds in the implanted silicon. It is observed that a nitrogen rich silicon oxynitride structure is formed after SHI irradiation. The study of X-ray rocking curves on the samples show the formation of small silicon crystallites due to swift heavy ion irradiation.
Vacuum, 2009
Silicon oxynitride (Si x O y N z ) buried insulating layers were synthesized by dual implantation of nitrogen ( 14 N þ ) and oxygen ( 16 O þ ) ions sequentially into single crystal silicon in the ratio 1:1 at 150 keV to ionfluences ranging from 1 Â 10 17 to 5 Â 10 17 cm À2 . Heavy ion elastic recoil analysis (HI-ERDA) studies of as implanted samples show Gaussian like distributions of nitrogen and oxygen. After annealing at 800 C, both the nitrogen and oxygen distributions appear as flat plateau like regions near projected range showing the formation of a continuous buried oxynitride layer. Micro-Raman study of as implanted samples shows a broad peak at 480 cm À1 for all fluences. It signifies a complete amorphization of silicon due to high fluence implantation. The annealing at 800 C results in the reduction of the intensity of the broad peak observed at 480 cm À1 and also gives rise to an additional peak at 517 cm À1 . It shows partial recrystallization of damaged silicon due to annealing. The X-ray rocking curves studies from highresolution X-ray diffraction (HRXRD) of the samples implanted with different fluences have also further confirmed partial recrystallization of damaged silicon on annealing.
Electrical creation of spin polarization in silicon at room temperature
Nature, 2009
The control and manipulation of the electron spin in semiconductors is central to spintronics 1,2 , which aims to represent digital information using spin orientation rather than electron charge. Such spin-based technologies may have a profound impact on nanoelectronics, data storage, and logic and computer architectures. Recently it has become possible to induce and detect spin polarization in otherwise non-magnetic semiconductors (gallium arsenide and silicon) using all-electrical structures 3-9 , but so far only at temperatures below 150 K and in n-type materials, which limits further development. Here we demonstrate room-temperature electrical injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect and the electrical detection of the induced spin accumulation. A spin splitting as large as 2.9 meV is created in n-type silicon, corresponding to an electron spin polarization of 4.6%. The extracted spin lifetime is greater than 140 ps for conduction electrons in heavily doped n-type silicon at 300 K and greater than 270 ps for holes in heavily doped p-type silicon at the same temperature. The spin diffusion length is greater than 230 nm for electrons and 310 nm for holes in the corresponding materials. These results open the way to the implementation of spin functionality in complementary silicon devices and electronic circuits operating at ambient temperature, and to the exploration of their prospects and the fundamental rules that govern their behaviour.
Electron spin resonance in thin film silicon after low temperature electron irradiation
Paramagnetic defects in amorphous and microcrystalline silicon (a-Si:H and μc-Si:H) with various structure compositions and doping levels were investigated by electron spin resonance (ESR). Samples were prepared by PECVD. The defect density was varied with 2 MeV electron bombardment at 100 K and stepwise annealing in the range of 80 K-433 K. In intrinsic material the spin density of the dominant ESR signal, presumably originating from dangling bonds (db), increases by up to 3 orders of magnitude after irradiation. In doped μc-Si:H material the pronounced conduction electron (CE) resonance disappears after irradiation and is replaced by the db resonance like in the irradiated intrinsic material. Generally the initial spin density and the line shape can be restored upon annealing at 433 K. Additional features at g-values of g ≈ 2.010 and g ≈ 2.000 in the ESR spectra are observed after irradiation together with the strongly enhanced Si db line at about g = 2.004-2.005. These features decrease rapidly on the first annealing steps and cannot be observed after the final annealing stage.
Structural studies of silicon oxynitride layers formed by low energy ion implantation
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2008
Silicon oxynitride (Si xO yN z) layers were synthesized by implanting 16O 2+ and 14N 2+ 30 keV ions in 1:1 ratio with fluences ranging from 5 × 10 16 to 1 × 10 18 ions cm -2 into single crystal silicon at room temperature. Rapid thermal annealing (RTA) of the samples was carried out at different temperatures in nitrogen ambient for 5 min. The FTIR studies show that the structures of ion-beam synthesized oxynitride layers are strongly dependent on total ion-fluence and annealing temperature. It is found that the structures formed at lower ion fluences (˜1 × 10 17 ions cm -2) are homogenous oxygen-rich silicon oxynitride. However, at higher fluence levels (˜1 × 10 18 ions cm -2) formation of homogenous nitrogen rich silicon oxynitride is observed due to ion-beam induced surface sputtering effects. The Micro-Raman studies on 1173 K annealed samples show formation of partially amorphous oxygen and nitrogen rich silicon oxynitride structures with crystalline silicon beneath it for lower and higher ion fluences, respectively. The Ellipsometry studies on 1173 K annealed samples show an increase in the thickness of silicon oxynitride layer with increasing ion fluence. The refractive index of the ion-beam synthesized layers is found to be in the range 1.54-1.96.
Modification of n Si characteristics by annealing and cooling at different rates
Active and Passive Electronic Components, 2003
The effect of annealing of the n-Si semiconductor on its characteristics in photoelectrochemical systems has been investigated. The annealing improved the dark current density vs. potential plots. The surface was improved by annealing, as manifested by SEM results. The effect of the cooling rate on preheated n-Si wafers was also investigated. It was found that the slowly cooled electrodes gave better dark current density vs. potential plots, for samples annealed at lower than 550 C. For samples annealed at higher temperatures, quenching gave better dark-current density vs. potential plots. SEM measurements showed parallel results to these findings. Enhanced surface textures were observed for slowly cooled wafers from temperatures below 550 C. Samples quenched from temperatures above 550 C showed better surfaces than slowly cooled counterparts.
MRS Proceedings, 1987
(100) silicon wafer• 8 weregimplanted with 200keV N+ ions to doses of 0.95 and l.lxl0O cm-at a temperature of 520 0 C, and then annealed at 1405 0 C for 30 minutes. We report here observations of the resulting microstructures. A buried o•-Si Na layer and a cgood quality silicon overlayer were found. Evidedce of cavities in the Si ~a layer was found in the higher dose sample. Our resul~s sua'cest that the cavities are associated with the delamination which sometimes occurs during annealingT.
Structural studies of 20 keV oxygen-implanted silicon
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Silicon wafers were implanted with 20 keV O 2 up to total¯uence of 1 Â 10 18 O 2 cm À2 to synthesize SiO 2 layers. The FTIR, ESR and C±V studies of as-implanted samples and samples nitrogen-annealed at 500°C and 800°C are reported. The FTIR spectrum of the as-implanted sample shows absorption bands corresponding to the stretching (1050 cm À1 , strong), the bending (800 cm À1 , weak) and the rocking (415 cm À1 , weak) modes of SiO 2 . The peaks shift towards higher wave number on annealing. The ESR signal of the as-implanted sample exhibits an isotropic g-value 2.0028, the line width 3.75 G and the spin density 1X1 Â 10 16 cm À2 which disappears on annealing at 800°C. The interface state density distribution as a U-shape and a minimum value of $7±8 Â 10 11 cm À2 eV À1 . Ó