(-a z) (1) where E(0) is the energy available on the surface of the component, u, the absorption coefficient and z the depth in the component.The energy loss along the z axis is given by (2). A. Laser interactionsLaser has proved its ability to induce SEE (Single Event Effect) [6]-[8], thanks to its capability to create localised ionising tracks in silicon.Laser interacts with silicon by photoelectric process. Hole-electron pairs are created along the beam. This interaction occurs only for wavelengths under 1.1 urn, that means for photon energy larger than silicon gap.According to the Beer-Lambert law, the laser energy available at a depth z (1) is a function of the initial energy and of the absorption coefficient u, The last is defmed for a given material and it depends strongly on the wavelength and on the doping level [3].The first part of this paper explains the laser interactions and the use of different wavelengths. A second part gives the SET results obtained at three wavelengths. At last, the calculation of sensitive depth and the comparison with heavy ion cross section curve are presented.Frontside irradiations can be done with any wavelength, the penetration depth decreasing with decreasing wavelength. But when performing frontside irradiations, the absorbing metallic layers hide some sensitive areas. Backside irradiations, on the contrary, give access to the whole component sensitive areas (see Fig. 1 ) [4] [9].Laser results are compared with heavy ion experimental data performed at DeL. Laser tests were performed with EADS laser facility. Our investigation method is based on threshold mapping which allows a detailed analysis of sensitive areas and their depth for each wavelength.."Abstract-The main objective of the work presented here is to explore the ability of laser irradiations to determine the SET sensitive depths of a linear device by using several wavelengths. Laser testing at two wavelengths allows the estimation of sensitive depths.

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