Yu Yuehui

Properties and structure of silicon nitride films synthesized by ion-beam-enhanced deposition

Abstract Silicon nitride films with a stoichiometric ratio of Si 3 N 4 were synthesized by ion-beam- enhanced deposition (IBED). It was observed that a silicon nitride film formed by IBED is composed of a thin silicon-enriched top layer, a stoichiometric Si 3 N 4 layer and a smooth transition layer at the interface next to the substrate. By detailed theoretical analysis and computer simulation of IR reflection interference spectra, refractive index profiles of the films were obtained. Composition profiles and refractive index profiles were correlated using the Lorentz-Lorenz equation. The fatigue and high temperature oxidation behaviour of metals can be improved using Si 3 N 4 coatings made by means of IBED, and the mechanisms of these are discussed.

SHRINKAGE EFFECTS OF POLYIMIDE FILM UNDER ION-BEAM IRRADIATION

Abstract Ion beam induced electrical conduction of ion implanted polyimide film could find potential applications for encapsulation of microelectronic devices and gate-transistor fabrication. One of the important problems to be solved is the shrinkage effect of polyimide film under ion beam irradiation. In this work the shrinkage effects of B + -implanted polyimide film under different implantation conditions were investigated by using different techniques (IR reflection interference spectra, surface profile measuring system, and automatic spreading resistance measurements). According to the previous results of ASR measurement a multilayer model of the implanted polyimide film was proposed for the computer simulation of infrared reflection interference spectra. The shrinkage and depth profile of the refraction index of the implanted polyimide films will be discussed.

OPTICAL-PROPERTIES AND MICROSTRUCTURE OF SILICON-NITRIDE FILM SYNTHESIZED BY ION-BEAM ENHANCED DEPOSITION

Abstract Silicon nitride films with a stoichiometric ratio of Si3N4 have been synthesized by concurrent electron beam evaporation of silicon and bombardment with nitrogen ions. Infrared reflection spectra in the wavenumber range 1500–5000 cm−1 were measured for the silicon nitride films. Interference fringes were observed in the IR spectra. By detailed theoretical analysis and computer simulation of the IR reflection interference spectra, refractive index profiles of the films were obtained. The chemical composition and interface structure of the IBED Si3N4 films have been investigated using Auger electron spectroscopy (AES) in conjunction with in-situ sputtering. The characteristic Auger spectrum for Si3N4 was measured. In-depth composition profiles and refractive index profiles have been correlated using the Lorentz-Lorenz equation. The results show that the refractive index profile determined by the IR reflection is consistent with that obtained from AES.

Infrared absorption and reflection spectroscopic studies of SOI structures formed by oxygen or nitrogen implantation

Abstract Silicon on insulator (SOI) structures have been formed by nitrogen or oxygen implantation with a dose of 1.8 × 10 18 ions/cm 2 at 190–200 keV. Infrared (IR) absorption and reflection spectra in the wavenumber range 400–5000 cm −1 were measured for SOI structures after various thermal anneal treatments. Localized vibrational modes and interference fringes were observed in the IR spectra. By IR absorption and thermodynamic analysis, it was found that crystalline α-Si 3 N 4 was formed in the buried nitride layer of SOI structure after annealing at 1200°C for 2 h. However, the buried layer formed by oxygen implantation was still amorphous SiO 2 after annealing at 1300°C for 5 h. By detailed theoretical analysis and computer simulation of the IR reflection interference spectra, refractive index profiles of SOI structures were obtained.

SOI STRUCTURE FORMED BY 95 KEV N2+ AND N+ IMPLANTATION AND EPITAXIAL-GROWTH

Abstract N-type 100 Si wafers were implanted with 95 keV, (0.1–1) × 1018 cm−2 N2+ and N+ and a beam current of 6 mA by using an ion implanter without mass analysis. The wafers were maintained at 500°C during implantation. After implantation the samples were annealed at 1200° C for 2 h and underwent vapor-phase epitaxial growth. The experimental results showed that the thicknesses of the top silicon layer with a minimum channeling yield of 5% are 0.3–1 μm and the thicknesses of buried Si3N4 layer are 170–200 nm. The buried silicon nitride layer consists of polycrystalline α-Si3N4 and nitrogen-rich nitride. The Si-Si3N4 interface is extremely abrupt, and the spreading resistance depth distribution is uniform in the top silicon layer. The results indicate that this method is an effective technology for forming cheap SOI material.

Optical Probing of Free-Carrier Plasma Effects of MeV Ion Implanted Silicon

Boron ions have been implanted into silicon at an incident energy of 3 MeV to a dose of 5×1015 cm-2. Buried conductive layers have been formed in the silicon substrate after annealing at 1050°C for 20s. Infrared (IR) reflection spectra in the wavenumber range of 500-4000 cm-1 have been measured and interference fringes related to free-carrier plasma effects observed. By detailed theoretical analysis and computer simulation of the IR reflection spectra, the depth profile of the carrier concentration, the carrier mobility near maximum carrier concentration, and the carrier activation efficiency have been obtained. The physical interpretation of the results was given.

Optical effects and microstructure of buried insulator layer formed by O+ and N+ Co-implantation

The microstructure and optical properties of a buried layer formed by O+ (200 keV, 1.8×1018/cm2) and N+ (180 keV, 4×1017/cm2) co-implantation and annealed at 1200°C for 2 h have been investigated by Auger electron, IR absorption and reflection spectroscopic measurements. The results show that the buried layer consists of silicon dioxide and SiOx (x<2) and the nitrogen segregates to the wings of the buried layer where it forms an oxynitride. By detail theoretical analysis and computer simulation of the IR reflection interference spectrum, the refractive index profiles of the buried layer were obtained.