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Tanner B.K.,Durham University | Garagorri J.,University of Navarra | Gorostegui-Colinas E.,University of Navarra | Elizalde M.R.,University of Navarra | And 3 more authors.
International Journal of Fracture | Year: 2015

The geometry of fracture associated with the propagation of cracks originating at the edges of (001) oriented, 200 mm diameter silicon wafers has been investigated under two regimes of high temperature processing. Under spike annealing, fracture did not occur on low index planes and all except one wafer exhibited crack patterns that started initially to run radially, but after a distance of typically 20–30 mm, turned and ran almost tangentially. Wafers subjected to plateau annealing, with a 60 s dwell time at high temperature, predominantly fractured through radial cracks running along $$\langle 110\rangle $$⟨110⟩ directions. X-ray diffraction imaging reveals substantial slip in all wafers subjected to plateau annealing. We demonstrate using finite element (FE) modelling that the change in fracture geometry is associated with this plastic deformation, which changes the stress distribution during the cooling phase of the rapid thermal annealing cycle. FE simulations without plastic relaxation show that the radial component of the thermal stress distribution is compressive in the centre of the wafer, causing the crack to run tangentially. Simulations incorporating temperature dependent plasticity showed that the equivalent stress becomes tensile when the plateau anneal allows time for significant plastic relaxation, permitting the crack to continue propagating linearly. © 2015, The Author(s).

Tanner B.K.,Durham University | Wittge J.,Albert Ludwigs University of Freiburg | Allen D.,Dublin City University | Fossati M.C.,Durham University | And 5 more authors.
Journal of Applied Crystallography | Year: 2011

High-resolution X-ray diffraction imaging of 200 mm silicon wafers following rapid thermal annealing at a temperature of 1270 K has revealed the presence of many early stage sources of thermal slip associated with the wafer edge. Dislocation sources are primarily at the wafer extremity, though many are generated by damage at the edge of the bevel incline on the wafer surface. A smaller fraction of sources is associated with other regions of localized damage, probably relating to protrusions on the wafer support. The geometry of the latter is similar to that of dislocation sources generated by controlled indentation on the wafer surface. It is concluded that rapid spike annealing at high temperature does not suppress the nucleation of slip, but rather the rapidity of the process prevents the propagation of the dislocations in the slip band into the wafer. © 2011 International Union of Crystallography Printed in Singapore - all rights reserved.

Garagorri J.,University of Navarra | Reyes Elizalde M.,University of Navarra | Fossati M.C.,Durham University | Jacques D.,Jordan Valley Semiconductors UK Ltd. | Tanner B.K.,Durham University
Journal of Applied Physics | Year: 2012

X-ray diffraction imaging of 200 mm diameter (100) oriented double-side polished silicon wafers has revealed that the slip band distribution, following rapid thermal annealing (RTA), has a lower symmetry than predicted from the material crystallography. Finite element (FE) modelling of the thermal processes has been undertaken and it is found that, in order to predict the measured temperature distribution during the annealing sequence in a commercial RTA furnace, an anisotropic heat flux distribution in the furnace must be included. When such an anisotropic heat flux is used to predict the wafer temperature, it is found that the temperature gradients are not equivalent in the radial direction. Calculation of the resolved shear stresses on the five independent slip systems associated with these gradients predicts asymmetry between the stress on slip bands that project into the [011] and [01̄1] directions. The anisotropy of the resolved shear stress distribution predicts accurately the asymmetry of the experimentally observed slip band length and density. Rotation of the wafer with respect to the furnace axes results in characteristic and systematic changes in the symmetry of the distribution, which is in good agreement with the finite element predictions. © 2012 American Institute of Physics.

Qi Z.,Dalian University of Technology | Huang H.,Dalian University of Technology | Cao T.,Dalian University of Technology | Liu P.,Dalian University of Technology | And 2 more authors.
Applied Optics | Year: 2013

A fiber pressure sensor with a collimator at the off-center position of a diaphragm is demonstrated. The detection mechanism is incident-angle sensitive rather than traditional working-distance sensitive. Due to the small beam divergence of the collimator, the control on working distance is less stringent, and high sensitivity can be realized because the coupling efficiency of the collimator is very sensitive to the incident angle decided by the off-center diaphragm reflection. Sensitivity of 1.11 and 0.16 dB/KPa can be achieved with silicon diaphragm thicknesses of 100 and 150 μm, respectively. Moreover, the detection range can be continually shifted by changing the pressure in the sealed diaphragm cavity. © 2013 Optical Society of America.

Tanner B.K.,Durham University | Fossati M.C.,Durham University | Garagorri J.,University of Navarra | Elizalde M.R.,University of Navarra | And 6 more authors.
Applied Physics Letters | Year: 2012

We show that x-ray diffraction imaging (topography) and finite-element modelling can determine accurately the probability of propagation of individual cracks in brittle single crystal materials. The x-ray image of the crack provides a critical parameter for crack propagation which informs a predictive model, enabling us to identify critical defects that lead to catastrophic shattering of silicon wafers during high temperature thermal processing. Wafers fracture on cooling and finite element modelling shows that, during cooling, the tangential stress at the wafer edge is tensile and results in crack propagation. The predicted fracture geometry agrees extremely well with that observed experimentally. © 2012 American Institute of Physics.

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