Papers by Keyword: Defect

Abstract: While batch wafer cleaning processes have been conventionally used in the semiconductor manufacturing for many years, the use of single wafer cleaning processes in the manufacturing has recently become increasingly widespread. Single wafer cleaning processes have the advantages of reducing particle and metal contamination, however, electric charge or electrostatic discharge phenomena occurring in these processes causes serious problems such as device destruction through insulation failure and circuit disconnection [1,2]. Well-known examples are the breakdown of the ultra-thin gate oxide and the dissolution of Cu wiring due to charging-up damage in de-ionized water rinsing, which occur during the single wafer wet cleaning process in semiconductor manufacturing. We investigated the problem of wafer defects caused by electrostatic discharge and characterized them using transmission electron microscope (TEM) and energy dispersive X-ray (EDX) analyses.

Abstract: Positron lifetime and coincidence Doppler broadening spectra for porous silica calcined at temperatures from 900 to 1500 oC have been measured. As the sintering temperatures increasing from 900 to 1000 oC, the height of the peaks of the ratio curves decrease, and the τ3 increases, which is due to the exclusion of the gas and the organic substance out of the cavities. As the sintering temperatures increasing from 1000 to 1250 oC, some of the defects were recovered, the grains of low quarts appearing and growing. This gives rise to the increase of the height of the peak of the ratio curve, and the decrease of lifetime (τ1,τ2 and τ3). As the sintering temperatures increasing from 1250 to 1500oC, the height of the peak of the ratio curve decreases, and the lifetime increases due to the phase transition of low quartz to cristobalite.

Abstract: Slow positron beam technique has been applied to measure the Doppler broadening spectra for single crystals of Cu, SiO2, graphite, virgin Si, and Si without oxide film. The results show that the Cu ratio curve shows a high peak due to Cu having 10 electrons in the 3d shells. The ratio curve of SiO2 is higher than that of graphite. For the single crystal of Cu, SiO2, graphite, and Si without oxide film, the S (W) parameters decrease (increase) as positron implantation energy increasing. Defects on the surface lead to higher S (lower W) value. For the virgin Si and the thermally grown SiO2-Si samples, the S (W) parameters increase (decrease) as positron implantation energy increasing. It can be due to Si atom at surface, with two dangling bonds, tend to form silicon oxide with O. The W parameter for the single crystal of Cu is relatively high as compared with that of the single crystals of SiO2 and graphite.

Abstract: Slow positron beam technique has been employed to study the defects of graphite, nanophase C, as well as the structural changes in un-doped, B-doped and S-doped diamond films with annealing temperatures. The results show that the concentration of defects in nanophase C is higher than that in graphite. The vacancy concentration in the S-doped diamond film is higher than that in un-doped one. The addition of small amount of B atoms leads to the decrease of the vacancy concentration in the film. The vacancy concentration in un-doped diamond film would decrease after annealing at temperature below 600°C, while vacancy concentration will increase after annealing at temperatures above 900°C. The vacancy concentration in the 40 Ω cm B-doped diamond film decreases at annealing temperatures higher than 200°C.

Abstract: ositron lifetime spectroscopy (PAS) and Coincidence Doppler broadening measurements have been performed in as-grown and annealing single crystal ZnO. The temperature dependence observed in annealed ZnO indicates that the defect is removed during annealing. By combining the Doppler broadening measurements, we infer that there isn′t hydrogen filling the zinc vacancy site in the as-grown ZnO due to the same characteristics in CDB for as-grown and annealed ZnO samples

Abstract: Defects induced by electron irradiation in Te-doped liquid-encapsulated Czochralski–grown GaSb were studied by the positron lifetime spectroscopy. The lifetime measurements under room temperature indicated there were VGa-related defects with a characteristic lifetime of 298 ps in the heavily Te-doped as-grown GaSb samples. The average lifetime increased with the increase of irradiation dose in lightly Te-doped GaSb,but the behavior was opposite in the heavily Te-doped samples. It should be due to the shift of Fermi level in heavily Te-doped GaSb and the occurrence of gallium vacancies in different charge states. In the temperature dependence measurements carried out on heavily Te-doped samples, we observed positron shallow trap, and this shallow trap should be attributed to positrons forming hyrogenlike Rydberg states with GaSb antisite defects.

Abstract: Positron annihilation lifetime (PAL) spectroscopy，photo-induced current transient spectroscopy (PICTS) and thermally stimulated current (TSC) have been employed to study the formation of compensation defects and their evolvement under iron phosphide (IP) ambience or pure phosphide (PP) ambience. In the formation of IP SI-InP, the diffusion of Fe atoms suppresses the formation of some open-volume defects. As to PP SI-InP, VInH4 complexes dissociate into acceptor vacancies VInHn(n-3)(n=0,1,2,3), which compensate residual donor type defects and make the sample semi-insulating. Electron irradiation-induced deep level defects have been studied by TSC in PP and IP SI-InP, respectively. In contrast to a high concentration of irradiation-induced defects in as-grown and PP annealed InP, IP SI-InP has a very low concentration of defects.

Abstract: Slow positron beam and coincidence Doppler broadening techniques have been used to follow temperature-induced defects and structural changes in Cz-Si with an initial oxygen content of 1.1×1018 cm-3. Oxygen is recognized as a peak at about 11.85×10-3m0c on the ratio curves. For Cz-Si annealed at 480 oC/15h or 600 oC/15h, the ratio curves show the presence of vacancy-like defects, but they are not associated with oxygen. For Cz-Si annealed at 480 oC/15h, then followed by a 600 oC/15h heat treatment, the ratio curves show the signal of O atom. The ratio curves of Cz-Si, thermally treated by a two-step (480oC/15h + 600oC/15h) pre-annealing, followed by a one-step annealing under different hydrostatic argon pressures and annealed temperatures, also show a peak at 11.85×10-3m0c. The height of the peak varies with different samples. Experimental results indicate that the SiO2 film will form on the surface of Cz-Si after the heat treatment.

Abstract: Cerium doped lutetium aluminium garnet (Lu3Al5O12:Ce, LuAG:Ce) displays particularly promising performance and has a great potential to be used in PET and SPECT. LuAG:Ce phosphors was synthesized with a simple sol-gel process. The structure was identified with XRD. Variations of luminescent properties and defects of LuAG:Ce phosphors with different heat-treatment temperatures and Ce3+-dope concentrations have been investigated, with the aid of emission spectra and positron annihilation lifetime measurements. The influence of defects on the luminescence properties was discussed.

Abstract: Using positron lifetime spectroscopy, we examined the evolution of defects in the Ti24Cr36V40 alloy prepared by arc-melting method during hydriding cycles. We found that the positron lifetime increases with increasing the pressure swing cycles. This behavior is well correlated with the degradation of hydrogen transfer change with the pressure swing cycles. The prolonged positron lifetime is attributed to dislocation-related defects. Both dislocations and vacancies bound at dislocations may act as positron trapping centers. After the heat treatment at 400oC, a partial recovery of positron lifetime was observed.