AC IMPEDANCE MEASUREMENTS OF MOISTURE IN INTERFACES BETWEEN EPOXY AND OXIDIZED SILICON.

The in-situ interfacial impedance technique was used to study the effects of moisture at 80C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A epoxy cured with diethylene triamine. 50 mV sinusoidal voltages were applied at frequencies from 10 sup (-3) to 10 sup 5 Hz. Bulk impedance measurements followed Randles behavior; conduction in the bulk epoxy was ionic, and was diffusion controlled at low frequencies. An additional conduction process between interfacial electrodes was observed even though a water layer did not condense in the interface. Through comparative use of linear network models, it was found that the "interfacial" conduction path represented a distributed bulk conduction in the epoxy with current leakage into the conductive silicon substrate.