Nanoscale <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi mathvariant="normal">W</a:mi><a:mrow><a:mn>1</a:mn><a:mo>−</a:mo><a:mi>x</a:mi></a:mrow></a:msub><a:msub><a:mi>Si</a:mi><a:mi>x</a:mi></a:msub></a:mrow></a:math> layers with different Si content were deposited by magnetron sputtering on amorphous silicon layers. The structure and stress evolution during deposition were monitored and in real time. Thus, it was possible to disentangle different origins of stress built-up (interface formation, phase formation, grain growth, and texture) on the nanoscale. It was found that the bcc phase with a composition-dependent texture forms at low Si content (less than 10% Si), but only above a critical thickness. At intermediate Si content <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mo>(</c:mo><c:mn>13.9</c:mn><c:mo>%</c:mo></c:mrow><c:mo> </c:mo><c:mtext>and</c:mtext><c:mo> </c:mo><c:mrow><c:mn>16.5</c:mn><c:mo>%</c:mo><c:mo> </c:mo><c:mi>Si</c:mi><c:mo>)</c:mo></c:mrow></c:math>, or low Si content and low thicknesses <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mo>(</d:mo><d:mo>≲</d:mo><d:mn>4.5</d:mn><d:mo> </d:mo><d:mi>nm</d:mi><d:mo>)</d:mo></d:mrow></d:math>, the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>β</e:mi></e:math> phase with A15 structure and coexisting phases (bcc or amorphous) form, while a single, amorphous phase is observed at high Si content <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:mo>(</f:mo><f:mo>≳</f:mo><f:mn>22</f:mn><f:mo>%</f:mo><f:mo> </f:mo><f:mi>Si</f:mi><f:mo>)</f:mo></f:mrow></f:math>. An A15 formation driven by impurities (O,C,N) was excluded by combined x-ray photoelectron spectroscopy and x-ray diffraction measurements on a second sample series. calculations of substitutional bcc and A15 <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:msub><g:mi mathvariant="normal">W</g:mi><g:mrow><g:mn>1</g:mn><g:mo>−</g:mo><g:mi>x</g:mi></g:mrow></g:msub><g:msub><g:mi>Si</g:mi><g:mi>x</g:mi></g:msub></g:mrow></g:math> alloys support the formation of A15 at higher Si content. The A15-containing interlayer should be taken into account when discussing the superconductivity of W/Si multilayers. The stress evolution during deposition of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:mrow><i:msub><i:mi mathvariant="normal">W</i:mi><i:mrow><i:mn>1</i:mn><i:mo>−</i:mo><i:mi>x</i:mi></i:mrow></i:msub><i:msub><i:mi>Si</i:mi><i:mi>x</i:mi></i:msub></i:mrow></i:math> was correlated with the microstructure evolution, and compared to similar observations for <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:msub><k:mi>Mo</k:mi><k:mrow><k:mn>1</k:mn><k:mo>−</k:mo><k:mi>x</k:mi></k:mrow></k:msub><k:msub><k:mi>Si</k:mi><k:mi>x</k:mi></k:msub></k:mrow></k:math>. Due to the crystalline phase (bcc/A15) and bcc texture ([111] and [110]) competition, the structure formation of <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mrow><l:msub><l:mi mathvariant="normal">W</l:mi><l:mrow><l:mn>1</l:mn><l:mo>−</l:mo><l:mi>x</l:mi></l:mrow></l:msub><l:msub><l:mi>Si</l:mi><l:mi>x</l:mi></l:msub></l:mrow></l:math> shows a higher complexity. This explains the wide range of stress states (from tensile to compressive) observed after deposition of <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mrow><n:msub><n:mi mathvariant="normal">W</n:mi><n:mrow><n:mn>1</n:mn><n:mo>−</n:mo><n:mi>x</n:mi></n:mrow></n:msub><n:msub><n:mi>Si</n:mi><n:mi>x</n:mi></n:msub></n:mrow></n:math>. Nanoscale W-Si based stress-compensation layers could be employed for tailoring the stress state of nonepitaxial semiconductor devices. Published by the American Physical Society 2024
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Krause et al. (2024) studied this question.