B8.3 - Application of Sacrificial Layers for the Modular Micro Sensor Fabrication on a Flexible Polymer Substrate

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
B8 - Magnetic Sensors
T. Griesbach, M. Wurz, L. Rissing - Leibniz Universität Hannover, Garbsen (Germany)
355 - 360


A concept for the fabrication of modular micro sensors on flexible substrates is presented in this paper. For the fabrication of micro sensors on flexible polymer substrates, investigations on sacrificial layers are essential, since it must be possible to release the sensors at the end of the fabrication process. This paper describes the development and fabrication of an anisotropic magneto-resistance (AMR) sensor on a 5 μm thick SU-8™ layer, which is an epoxy based photosensitive polymer. The micro sensor is fabricated on a standard Si wafer due to handling purposes during the sensor fabrication process. Initial investigations concentrated on the proof of the applicability of various sacrificial layers and the respective techniques required for the removal of these layers. To investigate the suitability of sacrificial layers for the fabrication of modular micro sensors, Cr and SiO2 were investigated as sacrificial materials. Additionally, investigations on the removal of the complete Si substrate were carried out. Cr layers within a certain thickness range were fabricated by sputter deposition and electron beam evaporation. For the deposition of the SiO2 layers, a plasma enhanced chemical vapor deposition (PECVD) process was used. For the removal of the sacrificial layer with the AMR sensors on the SU-8™ foil on top adequate processes were developed. The etching of the Si substrate was carried out wetchemically by caustic potash (KOH). For the etching of the SiO2 layers, hydrofluoric acid (HF) and for Cr, the commercial etching solution Selectipur® was used. Optimal process parameters were determined for the etching of Si and SiO2 sacrificial layers, respectively.