Application of Sacrificial Layers for the Modular Micro Sensor Fabrication on a Flexible Polymer Substrate

摘要

A concept for the fabrication of modular micro sensors on a flexible substrate is presented in this paper.rnFor the fabrication of micro sensors on flexible polymer substrates, investigations on sacrificial layers arernessential, since it must be possible to release the sensors at the end of the fabrication process. Thisrnpaper describes the development and fabrication of an anisotropic magneto-resistance (AMR) sensor onrna 5 μm thick SU-8? layer, which is an epoxy-based photosensitive polymer. The micro sensor isrnfabricated on a standard Si wafer due to handling purposes during the sensor fabrication process. Initialrninvestigations concentrated on the proof of the applicability of various sacrificial layer materials and thernprocess compatibility of the respective techniques required for the removal of these layers. To investigaternthe suitability of a sacrificial layer process for the fabrication of modular micro sensors, Cr and SiO_2 wererninvestigated as sacrificial layer materials. Additionally, investigations on the removal of the complete Sirnsubstrate were carried out. Cr layers were fabricated within a certain thickness range by sputterrndeposition and electron beam evaporation. For the deposition of the SiO_2 layers, a plasma enhancedrnchemical vapor deposition (PECVD) process was used. For the removal of the sacrificial layer with thernAMR sensors on the SU-8? foil on top, adequate processes were developed. The etching of the Sirnsubstrate was carried out wet-chemically by caustic potash (KOH). For etching the SiO_2 layers,rnhydrofluoric acid (HF) and for Cr etching, the commercial etchant Selectipur? was used. Optimal processrnparameters were determined for etching the Si and SiO_2 sacrificial layers, respectively.