Zhou Zuyao

Improved activation in Si+ and P+ dually implanted InP

Dual implantations of Si+ and P+ at elevated temperatures were used to study the amphoteric property of Si in InP. The electrical properties from Hall measurements indicate that improved activation is obtained in dually implanted samples, and in-diffusion of Si species is inhibited by implantation of P species. Photoluminescence spectra at 11 K proved that the implantation of P species can suppress the formation of deep Si acceptors formed from substantial Si at P sites effectively. All these results demonstrate that as in GaAs, Si is an amphoteric dopant in InP and that high carrier concentration can be attained by dual implantations.

SYNTHESIS OF SILICON-NITRIDE FILMS BY ION-BEAM ENHANCED DEPOSITION

Abstract Silicon nitride films with stoichiometric ratio of Si3N4 have been synthesized by concurrent electron beam evaporation of silicon and bombardment with nitrogen ions. The results show that the component ratio of nitrogen to silicon in IBED silicon nitride films can be controlled and predicted by the atomic arrival rate ratio of nitrogen to silicon. IR measurement shows that the characteristic absorption peak of IBED Si3N4 is located at a wavenumber of 840 cm−1. The refractive index ranges from 2.2 to 2.6. RBS, AES, TEM, SEM, ED and spreading resistance measurement were used for investigation of the depth profiles of composition and structure of silicon nitride films synthesized by IBED. An intermixed layer is formed at the interface by the knock on effect, and a silicon enriched layer is observed at the surface region of the film. Normally the films were found to be amorphous, but electron diffraction patterns taken from deposited layer showed a certain crystallinity. The silicon nitride films prepared by IBED have dramatically less oxygen content than that formed by non-ion-assisted deposition.

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.

Near-surface damage created in silicon by BF2+ implantation

Abstract The near-surface damage in silicon induced by the bombardment of 147 keV BF 2 + has been investigated by 2 MeV He + Rutherford-backscattering spectrometry. The implantation was carried out at room temperature with the ion doses ranging from ~ 10 13 to ~ 10 16 cm −2 . The radiation damage was compared with corresponding B + and F + atomic-ion implantation. A damage enhancement at the surface region of the silicon implanted with BF 2 + has been observed and it is attributed to the multiple-collision effect between molecular ions and host atoms.

ANALYSIS OF ELECTRICAL-PROPERTIES OF BURIED NITRIDE FORMED BY HIGH-DOSE N+ IMPLANTATION

N-type 〈100〉 crystalline silicon wafers were implanted by N+ at 170 keV with doses ranging from (0.5–2.2) × 1018/cm2. All these implanted wafers were annealed at 1200°C for 2 h in dry-N2 ambient. Infrared (IR) transmission spectroscopic measurements showed that a buried α-Si3N4 layer was formed for those wafers in which the dose of implanted N+ was higher than 1 × 1018/cm2. B+, Si+ and Ar+ were implanted into these wafers to amorphize the buried α-Si3N4 in order to improve its insulating properties. IR measurements indicated that Si+ and Ar+ implantations can amorphize the buried α-Si3N4. Though the deposited energy density of B+ was higher than that of Si+ and Ar+, buried α-Si3N4 cannot be amorphized by B+ implantation. These wafers were annealed at 900 and 1150°C for 45 min. Amorphized nitride recrystallized to form α-Si3N4 after annealing at 1150°C. Ohmic contacts were fabricated at front and back sides for all wafers by As+ implantation and aluminium evaporation. I–V characteristics were measured and the effect of B+, Si+, and Ar+ implantations on insulating properties of the buried insulator was studied for all samples.

RBS studies of As redistribution during silicide formation by RTA

Abstract A systematic RBS study of As-dopant redistribution during silicide formation by rapid thermal annealing (RTA) has been done for NiSi, CrSi and TaSi systems. Three kinds of As-implanted samples were studied: (1) metal layer on As-implanted Si; (2) As-implanted metal silicide on Si; and (3) As-implanted metal layer on Si. During silicide formation the As-dopants accumulate near the interface region, get incorporated in the silicide region or diffuse out of the silicide layer into the surrounding ambience. Differences in the dopant redistribution are due to the different initial locations relative to the moving species of silicide formation and their diffusivity at the temperatures of metal-silicon reaction.

IMPROVED ACTIVATION OF MG+ AND P+ DUAL IMPLANTATION INTO GAAS

Co-implantation of phosphorus was used to enhance the activation of the implanted magnesium in GaAs. Improved activations were observed in dually implanted samples by either furnace annealing or rapid thermal annealing. For dose of 5 × 1014 cm-2 Mg+, an activation of 74% with a sheet resistance 216Ω/ was obtained for dual implant compared to the activation of 33% and sheet resistance of 367Ω/ for single implant after rapid thermal annealing. The results suggest that the high carrier concentration can be obtained by this technique.

Investigation on mechanisms for ion Beam Induced Degradation of Polyimide

Three types of ions with different atomic masses (B , Ar and As ) were chosen to irradiate polyimide films in similar conditions in order to check mechanisms of the formation of ion beam induced damage in polyimide. A four-point probe technique was used to measure sheet resistivities of implanted films. An ion mass effect on conductivity of ion irradiated polyimide film was discovered. The ion mass effect on ion beam induced change of conductivity and on the energy loss process of the ions in polyimide suggest that the electronic energy loss of incident ions is an important factor for the increase of conductivity of implanted polyimide, and the contributions of recoil ionization are restricted by the grave damages as a result of nuclear energy loss process of ions in targets. Our hypothesis is supported by automatic spreading resistance measurement of B implanted polyimide film coated on silicon substrate. The results of this work have been compared with the hypothesis of degradation through direct knock on of atoms in polyimide, proposed by D.Fink et al [Nucl. Instr. and Meths B32 (1988) 125]