Papers by Author: V.D. Akhmetov

Abstract: The results of highly sensitive FTIR investigation, ab initio calculations and rate equation modeling of the early stages of oxide precipitation are compared. The attachment of interstitial oxygen to VOn is energetically more favorable than the attachment to On for n  6. For higher n the energy gain is comparable. The point defect species which were detected by highly sensitive FTIR in high oxygen Czochralski silicon wafers are O1, O2, O3, and VO4. Rate equation modeling for I, V, On and VOn with n = (1..4) also yields O1, O2, O3 to appear with decreasing concentration and VO4 as that one of the VOn species which would appear in the highest concentration after RTA.

Abstract: The gravitational induced shear stresses in 200 mm silicon wafers supported in verticaltype or horizontal-type furnace were calculated using 3D-FEM analysis of the displacement vector assuming linear elastic behavior of the anisotropic material. For comparison of the two complex loading cases and for relating the effect of gravitational constraints to the mechanical strength of the wafers, the invariant von Mises shear stress τM was chosen. The computed maximum values of τM demonstrate that the gravitational induced stress for vertical processing is approximately one order of magnitude less than the gravitational induced stress for horizontal processing. The experimental results obtained from processing of 200mm wafers with different oxygen concentration in horizontal and vertical boats at 1200°C are in an excellent agreement with the theoretical simulations.

Abstract: The evolution of nitrogen related infrared vibrational spectra of CZ-Si implanted with nitrogen, with doses 1017 ion/cm2 and 1018 ion/cm2, at 140 keV, was studied after annealing at 1130°C/5h under different hydrostatic pressures, from 1 bar to 10.7 kbar. It was found for each pressure applied, that the increased nitrogen dose leads to transformation of broadband spectra to the fine structure ones, corresponding to crystalline silicon nitride. The spectral position of observed sharp peaks in the investigated pressure region is red shifted in comparison to the peaks of crystalline silicon oxynitride found recently by other investigators in nitrogen-containing poly-Si as well as in a residual melt of nitrogen-doped CZ-Si. The application of pressure during annealing results in further red shift of the nitrogen-related bands. The observed decrease of frequency of vibrational bands is explained in terms of the pressure induced lowered incorporation of oxygen into growing oxynitride phase.