Metallization Corrosion in Silicon Devices by Moisture-Induced Electrolysis

In an investigation of the factors which determine the rate of electrolytic corrosion of the Al metallization in plastic-encapsulated ICs operated in a moist atmosphere, the surface conductivity of thermal SiO2 was measured as a function of relative humidity and temperature. Electrolysis in the water film adsorbed at high relative humidity produces either protection of the Al metallization by anodization or destructive corrosion at the anode and/or cathode. The occurrence of protection or destructive corrosion is mainly determined by the nature and amount of ionic impurities present in the water film and by temperature.