The rapid control of laser crystallisation during in-line large area flat panel display fabrication using polysilicon (poly-Si) thin-film transistors (TFT's) is of growing importance. In this work, the microstructural analysis of the laser irradiated area has been studied with atomic force microscopy (AFM) and phase stepping microscopy (PSM), the latter being an automated mode of interference microscopy that allows the rapid and non-destructive measurement of nanometric surface morphology. The evolution of the crystallisation process in amorphous silicon (a-Si) thin films irradiated using large and long duration (200 ns) excimer laser (308 nm) pulses as a function of different key parameters such as the laser fluence, the beam homogeneity and the number of laser shots has been studied. We show that PSM, although having a lower lateral resolution than AFM, is capable of detecting the important super lateral growth (SLG) region. From the comparison of the results obtained by interference microscopy and AFM, the PSM technique has been shown to be an interesting alternative way that could be used for the quantitative calibration of the laser annealing process in an industrial environment. (C) 2002 Elsevier Science B.V. All rights reserved.