A scanning photoelectron microscopy study of AlN/SixNy insulating stripes

Scanning photoelectron microscopy (SPEM) has been applied to measure a series of Al 2p images from a 900 nm thick AlN insulating overlayer covering a SixNy mesh on the Si substrate. The Al 2p core level exhibits an energy shift that is induced by the local charging. This energy shift depends on the thickness of the AlN/SixNy stripe, which is determined to be ∼0.12 eV/nm. The Al 2p SPEM images from the AlN/SixNy stripes change with different kinetic energies of the photoelectrons. The line width of the AlN/SixNy stripe varies from 4.5 to 11 μm. A “spatial-charging” model is proposed to explain those changes in the images. The present study shows that small local variations in insulating thickness can be monitored by the SPEM non-destructive technique.