Effects of Organic and Inorganic Dielectric Films on Semiconductor Devices

Departure of semiconductor-device performance from that expected on the basis of first-order models is often attributed to surface effects. One surface effect, channel conduction, is considered in terms of its relation to the electrical charge behavior of organic or inorganic dielectric films on semiconductor surfaces. Two cases of device failure due to charge instabilities in inorganic and organic dielectric layers are presented. In one, sodium ions drift in silicon oxide to induce a channel on a p-wall isolation region. Sodium ions can be sealed outside the oxide, thus preventing the drift and failure, by using silicon nitride as an ion barrier. A second example of dielectric-related device failure involves a plastic-encapsulated device. In this case, burn-in testing induces the migration of negative charges at the plastic-inorganic dielectric interface over an n-type region. The latter is inverted to p type. The resulting channel leakage current exceeds allowable limits and failure results.