Confocal imaging of porous silicon with a scanning laser macroscope/microscope

High resolution, large area photoluminescence mapping with scanning stage microscopes has proven to be a useful, but slow, quality control technique for compound semiconductor wafers. This paper describes a confocal scanning beam MACROscope-Microscope which can image specimens up to 7.5×7.5 cm in size, in less than 10s, using reflected light, photoluminescence, and optical beam induced current MACROscope mode provides 5 μm lateral resolution and 300 μm axial resolution. Microscope mode provides 0.25 μm lateral and 0.5 μm axial resolution, with a minimum field of view of 25×25 μm. This instrument can be used to evaluate preparation parameters involved in the manufacture of porous silicon as well as to provide quality control at a macroscopic and microscopic level for the fabrication of porous silicon specimens, wafers, detectors, and similar devices. A brief introduction to confocal microscopy and porous silicon is given. Several confocal and non-confocal photoluminescence and reflected-light images of a porous silicon wafer are shown at macroscopic and microscopic levels. A 3D profile of porous silicon structures reconstructed from confocal slices is also shown.