Depth detection and fabrication of porous silicon without the stress

Graphical abstract: Raman measurements showed that the phonon band within the etched layer shifting to lower frequencies is due to quantum confinement of phonons in the porous Si. Comparison of etched Si and bulk Si showed that etched Si exhibit much deeper detectable depth via the Raman spectrometer, presumably resulting from the pore formation. Therefore, the z-scan of Raman spectroscopy can be used to qualitatively detect the etching depth. - Highlights: • Porous Si without the stress was fabricated by electrochemical-etching method. • With the etching time increasing, pore diameter within the etched layer increases. • z-scan of Raman spectroscopy can be used to detect the etching depth. - Abstract: The stress in porous Si could affect the integration of porous Si devices with microelectronic integrated circuits based on silicon. In this paper, aligned macropore arrays without the stress were fabricated by an electrochemical etching procedure under a control voltage. The several etching stages of aligned macropore arrays were examined by microscopic technique, which indicates the variation in morphology from pore nuclei to aligned macropores with branching pores, and finally to aligned macropores without branching pores. Due to the difference of Raman peak positions between porous Si layer and substrate (unetched layer), furthermore, z-scan of Raman spectroscopy which is a nondestructive tool can be used to detect the etching depth. The difference should be ascribed to the quantum confinement of phonons in the porous Si.