Search

Time‐resolved reflectivity measurements have been used to investigate the morphology of an evolving amorphous‐crystalline interface during solid phase epitaxial regrowth of an ion‐implanted polycrystalline silicon film. Isothermal electron beam heating was used to produce partly regrown specimens for cross‐sectional transmission electron microscopy analysis, and this has enabled a direct correlation to be established between the interface shape and the observed reflectivity transients. Using a thin‐film optical model of an evolving rough interface, this correlation has enabled interface shapes to be inferred from the reflectivity at higher temperatures, where it is difficult to achieve partial regrowth. For undoped material, smaller grain sizes have been found to lead to rougher interfaces, with regrowth rates typically 20 times slower than for single crystal. At 620 °C, the presence of high concentrations of arsenic results in a smoother interface, but as the regrowth temperature is increased, the interf...

Experiments have been carried out to determine the temperature distributions induced during swept‐line electron‐beam heating of silicon. In situ measurements of the reflectivity were used to determine the temperature rise, using as a basis the rise in reflectivity exhibited by silicon with increasing temperature. Sweep speeds between 10 and 60 cm/s were studied using line beams between 60 and 300 μm wide. The experimental results were compared with analytic one‐ and two‐dimensional models assuming constant thermal properties, and with a one‐dimensional (1D) numerical model which takes into account the variation of heat capacity and thermal conductivity with temperature. The analytic models were used to show the range of conditions over which the 1D approximation could be applied and to quantify the errors introduced as this approximation breaks down. The experimentally measured peak temperatures and those predicted by the numerical model were found to agree to within 5% for conditions where the heat flow ...

Practical nonalloyed ohmic contacts on δ‐doped GaAs have been compared for AuGeNi (88:12:5) /and Cr metallizations to show the importance of metallization type for minimizing the contact resistance. They are shown to have low contact resistances even at 4.2 K and for contact sizes down to 240 nm diam. The effect of heating AuGeNi contacts to 270 °C is shown to be beneficial for large‐area contacts but not for submicron contacts, implying that nonuniformity is introduced.

Millisecond annealing using a dual electron beam annealer has been performed on 4 in. wafers for the activation of arsenic and boron difluoride source and drain implants as part of a complementary metal–oxide semiconductor process. Gross wafer distortion has been avoided by the use of a high background temperature and a synthesized line scan. Measurements of electrical activation of the implanted dopant indicates no metastable highly active phases, but activation to electrical solubility limits of longer lamp anneals performed at the same temperature. Measurements on transistors fabricated using single scan millisecond annealing show annealing cycle induced interface damage no worse than that seen in isothermal lamp anneals.

Microstructural changes occurring during the early stages of rapid thermal annealing of polycrystalline silicon bipolar emitters crucially affect the final dopant distribution and hence the performance of these devices. The first stage of annealing is epitaxial regrowth in the solid phase of the layer amorphised by the implantation. In-situ studies using time-resolved reflectivity measurements, combined with cross-sectional transmission electron microscopy of partly annealed structures, have determined the effects of initial grain size, annealing temperature and amorphising species (Si or As) on the rate of regrowth and the microstructural changes which occur during annealing. As the grain size is reduced, the regrowth rate decreases and the interface roughness increases. Arsenic implantation alters the rate of regrowth in such a manner as to produce a smoother interface than that in silicon implanted material.