Characterization of the Two-Photon Absorption Carrier Generation Region in Bulk Silicon Diodes

The pulsed laser has been a popular experimental method for interrogating single event effects (SEEs) in microelectronic devices and circuits for many years [1]. While particle accelerator testing is still considered to be the standard test method, the expense and availability of particle accelerator facilities suitable for SEE testing can often be limiting factors in thoroughly characterizing devices and circuits. Particle accelerator testing can also be destructive since devices can be exposed to a very high fluence of radiation, potentially resulting in device degradation. In addition to being more readily available and cost effective, laser testing offers deep insight into the spatial and temporal characteristics of SEEs that can be difficult or impossible to determine with broadbeam particle accelerator based test methods. Also, assuming the laser pulse energy is not excessively high, device degradation can be completely avoided. Because of these factors, SEE laser testing is an important resource for the the radiation effects community. SEE laser testing is often performed using laser light wavelengths above the bandgap. In this regime, Beer's law absorption dominates, and it can be assumed that for every one energetic photon incident on the semiconductor, one electron-hole pair will be created [1]. However, one limitation of choosing this approach is that the total laser penetration will exponentially attenuate beginning at the surface of the device under test (DUT). This requires that devices be tested from the topside, through any device overlayer materials that may be present. As metallization densities increase in device overlayers, topside laser testing can become difficult or impossible, due to shadowing effects. This was one limitation of topside laser testing that lead to the development of two-photon absorption (TPA) SEE laser testing [2].
Sponsored in part by the National Aeronautics and Space Administration (NASA).