Stress mapping on the porous silicon microcapsules by Raman microscopy

Silicon micromachined microcapsules have recently been used in biomedical applications as individual in sensing and drug delivery systems due to its biocompatibility and biodegradability properties. Microcapsules micromachining process is quite a complex procedure and to develop a high outcome the process has to be well controlled. One of the important physical characteristics influencing degradation of the microcapsules during the micromachining is a mechanical stresses in the microcapsules. In this work we investigated the stress in polysilicon microcapsules and their crystallinity before and after electrochemical etching process by means of micro-Raman spectroscopy and atomic force microscopy. It was shown that microcapsules fabrication process leads to the appearance of strong mechanical stress (up to 1.74 GPa), at the edges of produced microcapsules which can damage the structures. The combined AFM and Raman investigations confirm the presence of silicon amorphous phase after technological process and allow the stress mapping. We demonstrate a great potential of Raman stress imaging to be used for the testing of silicon microstructures and an improvement of fabrication process.