John R. Szedon

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.

An Approach for Evaluating Polymer Materials as Protective Coatings on Hybrid Microcircuits

Results are discussed of an evaluation program for polymer materials considered for applications as protective coatings on hybrid microcircuits. The general organization of the program was in terms of seven potential mechanisms by which coatings could fail to provide protection. Emphasis is on describing those six tests which developed differences in material behavior considered to be significant in terms of the general application. Three involved electrical performance of the films alone or in conjunction with hybrid circuit elements, two dealt with mechanical properties, and one with chemically related behavior. It is suggested that the tests could be used in selecting promising candidates for particular applications which relate to the test conditions or in understanding some failure modes which could be expected in complex hybrid microcircuit assemblies. A brief review is given of those tests which were not considered to develop distinctions between materials. As a point of exception, the role of organic coatings on bare semiconductor device surfaces was not investigated.