Abstract

External electro-optic probing of high-speed integrated circuits has been conducted by using a semiconductor laser diode and an organic poled polymer as both a sampling pulse source and a superstrate electric-field sensor. Even though polymeric sensors are completely in contact with ICs to increase sensitivity and spatial resolution, the capacitive loading effect is negligible because of a low dielectric constant (ε ~ 3). The poled polymers used are state-of-the-art methacrylate side-chain copolymers having an electro-optic coefficient r₃₃ of more than 10 pm/V at a wavelength of 1.3 μm. Poled polymeric films attached to substrates such as polyimides and glasses are diced into tiny chips of 1–2 mm square and directly bonded to the ICs tested. The laser pulse is incident upon the back side of the polymeric film at an angle of 50° and reflected off at the surface of the interconnect metallization. The longitudinal component of the electric field induces a change in polarization of the laser beam. Measurement at frequencies of over 20 GHz with near-shot-noise limited voltage sensitivity of less than 10-20 mV and internal node measurement of silicon submicrometer LSIs as well as GaAs ICs have been demonstrated.

© 1992 Optical Society of America