Publications

The Impact of Metal Line Reflections on Through-Wafer TPA SEE Testing

Khachatrian, Ani; Roche, Nicolas J.H.; Dodds, Nathaniel A.; McMorrow, Dale; Warner, Jeffrey H.; Buchner, Stephen P.; Reed, Robert A.

Charge-collection experiments and simulations designed to quantify the effects of reflections from metallization during through-wafer TPA testing are presented. The results reveal a strong dependence on metal line width and metal line position inside the {rm SiO}2 overlayer. The charge-collection enhancement is largest for the widest metal lines and the metal lines closest to the {rm Si}/{rm SiO}2 interface. The charge-collection enhancement is also dependent on incident laser pulse energy, an effect that is a consequence of higher-order optical nonlinearities induced by the ultrashort optical pulses. However, for the lines further away from the {rm Si}/{rm SiO}2 interface, variations in laser pulse energies affect the charge-collection enhancement to a lesser degree. Z-scan measurements reveal that the peak charge collection occurs when the axial position of the laser focal point is inside the Si substrate. There is a downward trend in peak collected-charge enhancement with the increase in laser pulse energies for the metal lines further away from the {rm Si}/{rm SiO}2 interface. Metallization enhances the collected charge by same amount regardless of the applied bias voltage. For thinner metal lines and laser pulse energies lower than 1 nJ, the collected charge enhancement due to metallization is negligible.