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Proceedings Paper

3D integration approaches for MEMS and CMOS sensors based on a Cu through-silicon-via technology and wafer level bonding
Author(s): L. Hofmann; S. Dempwolf; D. Reuter; R. Ecke; K. Gottfried; S. E. Schulz; R. Knechtel; T. Geßner
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Paper Abstract

Technologies for the 3D integration are described within this paper with respect to devices that have to retain a specific minimum wafer thickness for handling purposes (CMOS) and integrity of mechanical elements (MEMS). This implies Through-Silicon Vias (TSVs) with large dimensions and high aspect ratios (HAR). Moreover, as a main objective, the aspired TSV technology had to be universal and scalable with the designated utilization in a MEMS/CMOS foundry. Two TSV approaches are investigated and discussed, in which the TSVs were fabricated either before or after wafer thinning. One distinctive feature is an incomplete TSV Cu-filling, which avoids long processing and complex process control, while minimizing the thermomechanical stress between Cu and Si and related adverse effects in the device. However, the incomplete filling also includes various challenges regarding process integration. A method based on pattern plating is described, in which TSVs are metalized at the same time as the redistribution layer and which eliminates the need for additional planarization and patterning steps. For MEMS, the realization of a protective hermetically sealed capping is crucial, which is addressed in this paper by glass frit wafer level bonding and is discussed for hermetic sealing of MEMS inertial sensors. The TSV based 3D integration technologies are demonstrated on CMOS like test vehicle and on a MEMS device fabricated in Air Gap Insulated Microstructure (AIM) technology.

Paper Details

Date Published: 21 May 2015
PDF: 12 pages
Proc. SPIE 9517, Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems, 951709 (21 May 2015); doi: 10.1117/12.2178598
Show Author Affiliations
L. Hofmann, Fraunhofer-Institut für Elektronische Nanosysteme (Germany)
S. Dempwolf, X-FAB MEMS Foundry GmbH (Germany)
D. Reuter, Fraunhofer-Institut für Elektronische Nanosysteme (Germany)
R. Ecke, Fraunhofer-Institut für Elektronische Nanosysteme (Germany)
K. Gottfried, Fraunhofer-Institut für Elektronische Nanosysteme (Germany)
S. E. Schulz, Fraunhofer-Institut für Elektronische Nanosysteme (Germany)
R. Knechtel, X-FAB Semiconductor Foundries AG (Germany)
T. Geßner, Fraunhofer-Institut für Elektronische Nanosysteme (Germany)

Published in SPIE Proceedings Vol. 9517:
Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems
José Luis Sánchez-Rojas; Riccardo Brama, Editor(s)

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