IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 55, NO. 4, AUGUST 2008 2007 Probing SET Sensitive Volumes in Linear Devices Using Focused Laser Beam at Different Wavelengths Cecile Weulersse, Francoise Bezerra, Florent Miller, Thierry Carrière, Nadine Buard, and William Falo Abstract—The main objective of the work presented here is to explore the ability of laser irradiations to determine the SET sen- sitive depths of a linear device by using several wavelengths. Laser testing at two wavelengths allows the estimation of sensitive depths. The approach conducted here is applied for the first time to a linear device with very deep sensitive depth. The 1064 nm wavelength seems to be the most adequate one to reveal all sensitive areas and, when comparing with heavy ion experimental data, shows a rea- sonable agreement with heavy ion cross section. Index Terms—Laser-induced single-event effects, LM124 oper- ational amplifier, sensitive volume, sensitivity of linear ICs, single- event transient (SET). I. INTRODUCTION I N RECENT years, pulsed lasers have been used success- fully for Single Event Effects (SEE) investigations. Pre- vious studies have shown that this method is a reliable way to in- vestigate different SEE, even if there are significant differences in the mechanisms by which heavy ions and laser pulses phys- ically interact with semiconductor materials [1]–[4]. The vari- able-length charge tracks generated by a pulsed laser provide a unique method to probe the characteristics of the charge collec- tion volume of a semiconductor device and to estimate a charge collection depth [5]. Some accelerators are experiencing some problems for SEE testing, regarding the penetration depth of the heavy ions pro- duced. Laser testing at different wavelengths could be a way to determine the sensitive depth inside a component to check the ability of the heavy ions used to fully reveal its sensitivity. 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 results are compared with heavy ion experimental data performed at UCL HIF (Université Catholique de Lou- Manuscript received November 23, 2007; revised January 21, 2008, January 22, 2008, and February 4, 2008. Current version published September 19, 2008. C. Weulersse, F. Miller, and N. Buard are with the European Aero- nautic Defence and Space Company, Suresnes 92152, France (e-mail: cecile.weulersse@eads.net; florent.miller@eads.net; nadine.buard@eads.net). F. Bezerra is with CNES, Toulouse 31401, France (e-mail: francoise. bezerra@cnes.fr). T. Carrière is with the European Aeronautic Defence and Space Com- pany, Astrium Space Transportation, Les Mureaux 75016, France (e-mail: hierry.carriere@astrium.eads.net). W. Falo is with TRAD Tests and Radiations, Toulouse 31319, France (e-mail: william.falo@trad.fr). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TNS.2008.2000865 vain-Heavy Ion irradiation Facility). 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. 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. II. THE LASER TOOL FOR SEE INVESTIGATIONS A. Laser Interactions Laser has proved its ability to induce SEE [6]–[8], thanks to its capability to create localized ionizing tracks in silicon. Laser light interacts with silicon by photoelectric process and generates hole-electron pairs along the beam. This interaction occurs only for wavelengths under 1.1 m, that means at photon energies larger than silicon bandgap energy. According to the Beer–Lambert law, the laser energy avail- able at a depth (1) decreases exponentially with depth and is a function of the absorption coefficient . The last is defined for a given material and it depends strongly on the wavelength and on the doping level [3]. (1) where is the energy available on the surface of the compo- nent, , the absorption coefficient and the depth in the com- ponent. The energy loss along the axis is given by (2). (2) Front-side irradiations can be done with any wavelength, the penetration depth decreasing with decreasing wavelength. But when performing front-side illuminations, the reflective metallic layers obscure some sensitive areas. Backside irradia- tions, on the contrary, provide access to all of the component’s sensitive areas (see Fig. 1) [4] [9]. With a laser emitting at 1.06 m, the absorption coefficient is weak and thus backside irradiations can be performed without the need of thinning the silicon substrate. Laser light with a wavelength of 1.06 m is able to cross the whole device. For wavelength below 1.06 m, backside irradiations can also be performed but only if the substrate is thinned. B. Use of Different Wavelengths Table I lists the absorption coefficient for the three wave- lengths used as well as their corresponding penetration depths, 0018-9499/$25.00 © 2008 IEEE