Vol 47, No 6 (2018)

The effect of homoepitaxial Si(001) growth on the surface morphology during the annealing of a substrate by passing a direct current is examined by in situ high-vacuum reflection electron microscopy at a temperature of 1100°С and ex situ atomic force microscopy. The nonmonotonic dependence of the average distance between step bunch on the atomic flow to the surface under the growth conditions and the monotonic behavior under the sublimation conditions are established. The increase in the average distance between pairs of inclined steps between the bunches at an external atomic flow comparable with the flow of atoms evaporated from the surface during sublimation is found.

Several experimental methods for controlling the quality of the multilayer film structures used for the fabrication of magnetic tunneling junctions (MTJs) are considered. A multilayer magnetoresistive structure of the following composition is deposited using magnetron sputtering on a Singulus Timaris cluster tool: Ta/CuN/Ta/NiFe/IrMn/CoFe/Ru/CoFeB/MgO/CoFeB/Ta/Ru. A layer-by-layer elemental analysis of the composition of the deposited structure is carried out by the time of flight (TOF) secondary ion mass-spectrometry on a TOF.SIMS 5 installation. A cross section of the structure is analyzed using transmission electron microscopy (TEM) (Tecnai G2 F20 U-TWIN). The crystal structure of the layers is characterized using X-ray diffraction. A comparison of the data obtained using different analytical methods lets us estimate the accuracy of the analysis and the quality of the structure intended for further MTJ fabrication.

The results of investigations on the influence of the nonparallelism of electrodes on electromechanical interactions in imbalanced Micro Electro Mechanical Systems (MEMS) with comb electrode structures in the modes with a controllable voltage and charge are presented. The formulas for the calculation of the potential energy, electrostatic force, critical voltage, critical charge, and the magnitude of critical displacement of a movable electrode under different inclinations of the electrodes, which are necessary for the MEMS design, taking into account their real design features, are derived. It was stated that increasing the mutual inclination and the number of electrodes reduces the modulation depth of the capacitance C_max/C_min of the imbalanced capacitors with nonparallel electrodes, which can significantly limit the achievable modulation depth of the capacitance of tunable MEMS, especially when there are a large number of electrodes. It is revealed that in imbalanced MEMS, in the case of controllable voltage, when increasing the relative inclination of the electrodes, the electrostatic attraction force between charged electrodes decreases and the magnitudes of the critical voltage and displacement increase. Increasing the number of electrodes of an imbalanced capacitor will lead to a decrease in the range of the controllable displacement of the movable electrodes and the magnitude of the critical voltage. It is stated that under an invariable charge and nonparallel electrodes in imbalanced MEMS with a comb electrode structure a pull-in effect appears. When increasing the relative inclination of the electrodes, the electrostatic attraction force between the charged electrodes increases and the quantities of the critical charge and displacement decrease. When increasing the number of electrodes in imbalanced MEMS with a comb electrode structure in the invariable charge mode, the value of the critical displacement decreases monotonically and the magnitude of the critical charge rises.

Using an imitational cellular-automaton model, the structural degradation of a interlayer low-K dielectric during the plasma etching etching of a photoresist is studied. The dielectric represents a porous material based on SiOCH, whose integral dielectric permittivity depends on the percentage of carbon atoms on the pore walls and in the dielectric matrix. The period of etching is such that the removal of carbon (and, accordingly, degradation) is incomplete. The simulation is performed for 2 million steps of the automaton, which correspond to 2 s in the real process. During this period, the number of methyl groups does not exceed 20% of the initial value at the dielectric pore depth of 40 nm; in this case, the permittivity ε increases from 2.5 to 2.84. Extrapolating to a longer time period (nearly 1 min) shows that the total fraction of СН₃-groups is 9% of the initial value through the full depth of the material, while the final value of dielectric permittivity would correspond to 3.0–3.1. The results of the modeling agree with the experimental data described in the literature.

Halogen-containing plasma, in particular, freons, is frequently used to form the surface topology of semiconductors. In this paper, the kinetics of the interaction between freon R-12 and its mixture with argon and the surface of gallium arsenide (GaAs) are studied. It is established that the initial molecule is completely decomposed into atomic carbon within the studied range of conditions. It is confirmed that chlorine atoms are the main chemically active particles that ensure the etching of GaAs. It is demonstrated that the process of etching occurs in the ion-stimulated chemical reaction regime, where the desorption of products under ionic bombardment plays a substantial part in the purification of the surface. The spectral composition of the plasma-forming medium in the presence of a semiconducting GaAs plate is studied. Some reference lines and bands have been selected for the spectral monitoring of the etching rate by the intensity of the lines and bands of the etching products. In this work, the surface of specimens was monitored on a Solver P47Pro atomic force microscope.