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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
S.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
Englisch
Konferenzbeitrag
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/dokumente/N-555715.html