Overview of industrial customer projects in the area of MEMS technologies and applications
Fraunhofer IMS has both a CMOS clean room and amicrosystems technology Lab&Fab. In our microsystems technology Lab&Fab different functionalities can be integrated onto wafers from the CMOS line, like MEMS sensors or actuators, functional layers or several wafers can be integrated three-dimensionally. Our portfolio of MEMS applications developed with industrial customers contains, for example, pressure sensors for up to 2000 bar and with operating temperatures of up to 300 °C. The underlying MEMS technology is used, apart from the classic pressure measurement, for vibration sensors, microphones and sound generators.
Solar cells can be manufactured and integrated with CMOS and therefore allow for the supply of self-sufficient sensors. Trench condensators are available as energy storage. Fraunhofer IMS develops CMOS-compatible thermopiles that are especially suited for space-efficient imagers due to the integration via post-processing. Biosensor technology is addressed using acoustic mass sensors: With Flexural Plate Wave und Surface Acoustic Wave sensors biologically interesting substances can be proved on suitably functionalized membranes in a high temporal resolution. Freestanding nanostructures can be realized in a variety of shapes and materials through our sacrificial layer technology with gas phase etching and Atomic-Layer-Deposition (ALD).
Production of image sensors in the MST Lab&Fab
For image sensors the 3D-Integration via waferbonding or SLID (Solid-Liquid-Interdiffusion)-Bonding can be used for a processing directly on the pixel of complex or performance-critical signals. The substrates and technologies of the sensor system can be adapted on the sensor and signal processing requirements. For the electrical connection of several wafers is a wide selection of different technologies available, like TSVs (Through-Silicon-Vias) or Copper-Tin-Bumps. Apart from the image sensor technology in the visible range, the focus is also on near-infrared which is applied for runtime measurements (Time of Flight, ToF) and therefore 3D image sensor technology. The spectral range of the far-infrared (FIR) is addressed with a CMOS-integrated bolometer with 320 x 256 pixels. The integration of the infrared sensor on the CMOS wafer is carried out in the MST Lab&Fab.
Foundry services in the MST Lab&Fab
Apart from the complete MEMS solutions, Fraunhofer IMS also offers foundry services in the microsystems technology Lab&Fab. The clean room has lithography up to 0.35 µm available with the possibility to adjust the back and the front with 200 nm accuracy. Apart from the standard photoresist, colored resist and resist thickness of up to 40 µm are possible as well. With dedicated facilities fully integrated wafers can be bonded (direct wafer bonding) or individual circuits can be bonded on wafers (chip-to-wafer bonding). For plasma processes, we offer sputtering (PV), PE-CVD and reactive ion etching (RIE) as well as deep reactive ion etching (DRIE). Fields of expertise are the deposition of pure boron as ultrathin passivation or contacting, silicon carbide, germanium and differently doped amorphous silicon. Using electroplating, layers and structures of up to 40 µm can be created from gold, copper, tin and nickel. Atomic Layer Deposition (ALD) is perfectly suited for highly conformal, biocompatible passivation and, due to the excellent conformity, for many MEMS applications. A variety of oxides and nitrides as well as metallic layers, e.g. from titanium nitride and ruthenium, are possible.
Due to the low temperature, the processes are suited for post-CMOS integration. Extensive characterization and analytics support the development and allow a precise control systems. In addition, the MST Lab&Fab offers a 3D microscope, an atomic force microscope (AFM), an electron microscope (REM) with EDX, a scanning electron microscope for critical structures (CD-SEM), ellipsometers and profilometers.