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Hermeticity of SI1-XGeX diaphragms for the fabrication of a capacitive post-CMOS pressure sensor

 
: Walk, Christian; Netaev, Alexander; Wiemann, Matthias; Görtz, Michael; Vogt, Holger; Mokwa, Wilfried; Seidl, Karsten

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Institute of Electrical and Electronics Engineers -IEEE-:
20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII, TRANSDUCERS & EUROSENSORS 2019 : 23-27 June 2019, Berlin, Germany
Piscataway, NJ: IEEE, 2019
ISBN: 978-1-5386-8104-6
ISBN: 978-1-5386-8105-3
pp.1862-1865
International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers) <20, 2019, Berlin>
European Conference on Solid-State Transducers (Eurosensors) <33, 2019, Berlin>
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
16FMD01K
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
16FMD02
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
16FMD03
English
Conference Paper
Fraunhofer IMS ()
post-CMOS; pressure sensor; Siliciumgermanium (SiGe); hermeticity

Abstract
In this work, the hermeticity of diaphragm structures is investigated and optimized. The diaphragms are developed for the monolithic post-CMOS integration of capacitive pressure sensors. Si1-XGeX is used as diaphragm material and was deposited at temperatures below 400 °C. The hermeticity of the diaphragms was evaluated at a He pressure of 1800 hPa and in a temperature range from 50 °C to about 100 °C. The diffusion coefficients were determined by measuring the changes of diaphragm deflections due to He-diffusion inside the cavity. In the CVD process of Si1-XGeX cover layer on a polycrystalline p+Si1-XGeX diaphragm for closing the etch access holes, a variation of the SiH4 and GeH4 gas flows at a substrate temperature of about 380 °C was investigated regarding the selectivity of the layer growth on different surfaces (p+Si1-XGeX, Si, and SiO2). The selectivity of the layer growth against Si and SiO2 increases with the GeH4 ratio in the process gas flow. With a pure GeH4 gas flow, an optimisation of the parameters selectivity, He-diffusion and intrinsic stress of the Si1-XGeX cover layer was found.

: http://publica.fraunhofer.de/documents/N-555715.html