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Stress induced by the thermal gradients near the meltsolid interface affects the intrinsic point defect properties and the quality of single crystal Si grown from a melt. Also during device processing, stress in the Si substrate influences point defect behavior during thermal treatments. To be able to simulate and control the stress distribution one needs to know the elastic constants of single crystal Si at high temperatures. In the present study, the vibrational properties of single crystal Si samples are studied between room and melt temperature using the impulse excitation technique. From the measurements, the temperature dependent Young's moduli E〈ijk〉 of moderately doped Czochralski‐grown Si samples are extracted in the 〈100〉, 〈110〉 and 〈111〉 crystallographic directions. Close to the melt temperature, very high Young's moduli values between 110 and 160 GPa are obtained, depending on the crystallographic direction. Empiric expressions are derived for the temperature dependence of E〈100〉, E〈110〉 and E〈111〉 and of the elastic compliances s11 and s12 + s44/2, useful for application in process simulation. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The vibrational properties of single crystal Si and Ge are studied between room and melting temperature Tm using the impulse excitation technique. From the measurements, the temperature dependent Young's moduli E are extracted in the <100>-, <110>-and <111>-directions. For both semiconductors, the Young's moduli decrease smoothly with increasing temperature and retain high values up to Tm. Using the semi-empiric Wachtman's equation allows an excellent fit to the experimental data for the temperature dependence of E<100>, E<110> and E<111> between room temperature and 0.6Tm,. For higher temperatures, the Young's moduli decrease faster than predicted by Wachtman's equation. In the case of Ge, an apparent enhanced softening is observed starting from about 850 ºC which is due to a loss of Ge material, leading to a decrease of sample dimensions and weight.