Published online by Cambridge University Press: 01 February 2011
An automatic gas cell photoacoustic microscope has been used to characterize two laser machined air trenches in a silicon substrate from the back side. Both amplitude and phase images reveal the subsurface features. The frequency dependence of the photoacoustic signals with different laser spot sizes was compared with a 1-D model. The effect of lateral heat diffusion on subsurface defect characterization was investigated and the results can be applied to other photothermal techniques.