3D interconnect technologies for advanced MEMS/NEMS applications

3D integration and wafer level packaging (WLP) with through-silicon vias offer benefits like reduced footprint and improved performance. CMOS imaging sensors is one of the first successful introductions of a product with TSVs on the market, and 3D integrated memory stacks are expected to follow soon. Also sensor and actuator systems based on micro- and nano-electromechanical systems (MEMS/NEMS) will greatly benefit from WLP and 3D integration of the transducers and their readout and controller ICs. Ultimately, heterogeneous integration of different device technologies will allow the fabrication of MEMS/IC and NEMS/IC products with new and improved functionalities. For this to become a reality, cost-effective and reliable 3D integration technologies need to be developed. This paper gives an overview and reports on the current status of 3D interconnect technologies that will enable 3D integration for advanced MEMS/NEMS applications

Metal Films for MEMS Pressure Sensors: Comparison of Al, Ti, Al-Ti Alloy and Al/Ti Film Stacks

Thermo-mechanical stability of metal structures is one of the key factors affecting accuracy of micro-electromechanical (MEMS) piezoresistive pressure sensors. In this work, we present the measurement results of stress and hysteresis for the following metals deposited in the same sputtering equipment -Al, Ti, Al-Ti alloy and stacks of Al/Ti films-enabling, for the first time, a direct comparison between their thermo-mechanical properties supported with analysis of surface morphology (grain size, hillocks and voids)

Methods for characterization of wafer-level encapsulation applied on silicon to LTCC anodic bonding

This paper presents initial results on generic characterization methods for wafer-level encapsulation. The methods, developed specifically to evaluate anodic bonding of low-temperature cofired ceramics (LTCC) to Si, are generally applicable to wafer-level encapsulation. Different microelectromechanical system (MEMS) structures positioned over the whole wafer provide local information about the bond quality. The structures include (i) resonating cantilevers as pressure sensors for bond hermeticity, (ii) resonating bridges as stress sensors for measuring the stress induced by the bonding and (iii) frames/mesas for pull tests. These MEMS structures have been designed, fabricated and characterized indicating that local information can easily be obtained. Buried electrodes to enable localized bonding have been implemented and their effectiveness is indicated from first results of the novel Si to LTCC anodic bonding