Atom redistribution during crystallization of a B and P co-doped amorphous Si layer produced by Si and P chemical vapor co-deposition and B implantation has been investigated. The crystallization of the entire layer is quasi-instantaneous for annealing temperature greater than 650 °C. The crystallization rate is well reproduced by the Avrami-Johnson-Mehl-Kolmogorov model of transformation. The Avrami n is found equal to 4, which is corresponding to 3D bulk crystallization. Crystallization promotes a non-Fickian redistribution of B atoms, allowing for an abrupt interface between B-doped and B-undoped regions. After crystallization, B diffuses in the polycrystalline Si layer for concentrations lower than 1.5 1020 at cm3 via the type B kinetic regime. Crystallization has no significant (or detectable) influence on the P profile. For temperatures higher than 750 °C, P diffuses in the poly-Si layer towards the region of highest B concentration via the type B kinetic regime, leading to P uphill diffusion. This phenomenon can be simulated considering chemical interactions between B and P atoms in both grains and grain boundaries.
We have investigated the redistribution of B during the crystallization of an amorphous Si layer homogeneously doped with P. The redistribution of B only occurs for concentrations lower than 2 × 1020 at cm−3. Crystallization leads to a non “Fickian” redistribution, allowing an abrupt interface between the regions doped and undoped with B. Once the crystallization is ended, B diffuses through the layer in the type B regime with a coefficient which is in agreement with the literature data for diffusion in polycrystalline Si. Although the P distribution is homogeneous in the entire layer, for a temperature as high as 755 °C, P diffuses towards the region the most concentrated in B. The B and P interactions are interpreted as chemical interactions.
The kinetics of CoSi2 formation via a solid-state reaction between CoSi and single crystal Si has been the object of many studies in the past. Because of the importance of nucleation, complex kinetics has been reported. In this work, we investigate CoSi2 formation kinetics with in-situ diffraction during isothermal annealing of CoSi films on Si (100). In-situ measurements allow capturing the initial stage of CoSi2 formation. An initial t3/2 time-dependent evolution is observed and attributed to 3D growth of individual nuclei. This first regime is followed after the coalescence of the nuclei by a classical parabolic t1/2 one-dimensional film growth. We evidence a marked influence of the initial Co thickness (50 nm vs 10 nm) on the growth kinetics. A significant slowdown of the CoSi2 formation kinetics is observed for the thinnest film, whereas the activation energy remains the same. These results shine a new light on the complex formation kinetics of CoSi2 during solid-state reaction between CoSi and single crystal silicon and bring new knowledge about what occurs in the ultra-thin film regime, which is important for nanotechnologies.
To passivate Si − SiO 2 dangling bonds, metal–oxide–semiconductor field‐effect transistor devices are usually treated with hydrogen. Herein, the effects of such a treatment on the crystallization behavior on N‐doped, Ge‐rich Ge 2 Sb 2 Te 5 phase‐change materials for memory applications are investigated using synchrotron X‐ray diffraction (XRD) in situ during heat treatment. Uniform thin films, and laterally confined, metallized ones (simulating devices of different complexity) of initially amorphous N‐doped GGST are investigated. The specimens are heated up to 450–500 °C at a rate of 2 °C/min. Some of the specimens are treated with H/D; the equivalent untreated specimen is investigated for each of them. Crystallization onsets are estimated by quantification of the crystallized quantity during material transformation from the XRD patterns. In thin films, the hydrogen treatment results in lowered crystallization temperatures of the emerging cubic, metastable Ge 2 Sb 2 Te 5 phase. Its trigonal, thermodynamically stable polymorph always forms, but its crystallization temperature is unchanged. Patterned and metallized samples show less differences, are strongly textured, and no trigonal phase is observed. It is shown that certain questions might only be answered at large‐scale facilities where high energy photons are available at high flux, allowing data acquisition during the annealing process with a temperature resolution sufficient for a fine description of the sample transformation.
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