The Production of Vacancy-Oxygen Defects in Electron-Irradiated Cz-Si Initially Treated at High Temperatures and High Pressures

We report studies of defects in electron-irradiated Czochralski-grown silicon (Cz-Si) subjected to thermal treatments at 1000oC and 1130oC with or without the application of high hydrostatic pressure of ~ 11 Kbars, prior to irradiation. The work is primarily focused on the impact of the pre-treatments on the production rate of the VO defect and its conversion to the VO2 defect. To this end, IR spectroscopy measurements were carried out and the amplitudes of the VO band (830 cm-1) and the VO2 band (888 cm-1) were monitored in the course of an isochronal anneal sequence up to ~ 550oC. Thermal treatments at 1000oC result in a reduction of the production rate of the VO defect. This rate however increases when pressure is applied during the treatment. The opposite behavior is observed for thermal treatments at 1130oC. The production rate of the VO increases slightly in heat treated samples but decreases substantially when high pressure is applied. Similar trends show the conversion of the VO to the VO2 defect for the corresponding treatments. The results are discussed taking into account the oxygen precipitates formed at the various treatments and their impact on the amount of primary defects available during irradiation which affects the production of the vacancy-oxygen defects.

Using Quantitative TEM Analysis of Implant Damage to Study Surface Recombination Velocity in Silicon

Silicon wafers with shallow trench isolation structures 3700Å deep were self-implanted with silicon at 40keV, and a dose of 1E15/cm2. This produced an amorphous layer 1000Å deep. The samples were subsequently annealed at temperatures ranging from 750°C to 900°C. The excess interstitials can recombine at the “surface” created by the proximity to the trench sidewall. Plan-view TEM was used to quantify the dislocation distribution as a function of distance from the trench sidewall. It was found that there was no measurable change in defect density as a function of distance from the trench. This was true for both the 20 minute isochronal anneal, and the isothermal study 750°C. This suggests there is a relatively weak recombination of interstitials at the surface. This is surprising given most of the TCAD models assume a very fast surface recombination velocity.

Dopant diffusion in amorphous silicon

ABSTRACTIn this work we investigate the diffusion of high-concentration ultrashallow boron, fluorine, phosphorus, and arsenic profiles in amorphous silicon. We demonstrate that boron diffuses at high concentrations in amorphous silicon during low-temperature thermal annealing. Isothermal and isochronal anneal sequences indicate that there is an initial transient enhancement of diffusion. We have observed this transient diffusion characteristic both in amorphous silicon preamorphized by germanium ion implantation and also in amorphous silicon preamorphized by silicon ion implantation. We also show that the boron diffusivity in the amorphous region is similar with and without fluorine, and that the lack of diffusion for low-concentration boron profiles indicates that boron diffusion in amorphous silicon is driven by high concentrations. Ultrashallow high-concentration fluorine profiles diffuse quite rapidly in amorphous silicon, and like boron, undergo a definite transient enhancement. In contrast, ultrashallow high- concentration phosphorus and arsenic profiles did not significantly diffuse in our experiments.

Study of cluster-assembled nanophase copper using NMR

Cu NMR spectra from cluster-assembled nanophase copper with an average grain size between 5 and 10 nm show a broadened peak, at the normal Knight-shifted frequency for copper metal, which arises from only the central 1/2 to −1/2 transition. The broadening of the central line is associated with a distribution of Knight shifts. A very broad background is observed on either side of that peak, associated with broadening due to internal electric field gradients. Pulsed NMR measurements of the central peak show that virtually all the copper signals are significantly broadened and have a spin-spin relaxation time longer than larger-grained copper samples. The strain within the grains is estimated to be 0.7%. Line shape measurements as a function of spin echo delay time show there are a number of copper sites with longer relaxation times which have a significantly larger broadening. Those sites are tentatively identified as being at or near a grain boundary or free surface. A small orientation effect is observed indicating an anisotropy within the samples. An isochronal anneal of one sample showed significant line narrowing after an anneal at 450 °C consistent with other nanophase metals which show grain growth above 40-50% of the absolute melting temperature. The dependence of NMR linewidth on average grain diameter is estimated.

Nmr Study of Cluster-Assembled Nanophase Copper

ABSTRACT63Cu and 65Cu NMR spectra from cluster-assembled nanophase copper with an average grain size between 5 and 10nm show a broadened peak, at the normal Knight-shifted frequency for copper metal, which arises from only the central 1/2 to -1/2 transition. A very broad background is observed on either side of that peak. Some samples exhibit a second broad peak at a position normally associated with non-metallic copper. Pulsed NMR measurements of the central peak show that virtually all the copper signals are significantly broadened and have a spin-spin relaxation time longer than larger grained copper samples. Line shape measurements, using spin echoes, as a function of delay between rf excitation and measurement show there are a number of copper sites with longer relaxation times which have a significantly larger broadening. Those sites are tentatively identified as being at or near a grain boundary or free surface. A small orientation effect is observed indicating an anisotropy within the samples. An isochronal anneal of one sample showed significant, but not complete, line narrowing after an anneal at 450°C consistent with other nanophase metals which show grain growth above 40-50% of the melting temperature.

DLTS Characterization of N-Type Silicon After Rapid Thermal Annealing of Boron Implantation

ABSTRACTDLTS measurements show that majority-carrier traps exist after quartz-lamp, rapid-thermal annealing (RTA) activation of B+ and BF2+ ion implants in n-type silicon. Levels at Ec-0.17, 0.27, 0.44 and 0.57 eV annealed out with an additional 20 minute isochronal anneal at 550°C in argon. A stable defect at 0.37 eV existed at temperatures above 750°C. DLTS measurements of a Schottky diode on n-type silicon after only RTA indicated that electron traps could be introduced into n-type silicon by the RTA alone.