Bulk and Surface Conduction in CVD SiO and PSG Passivation Layers

Measurements of electrical conduction in the bulk of chemical vapor de-posited (CVD) SiO.2 and phosphosilicate glass (PSG) passivation layers typi-cally used for over-me~al IC protection are reported. Moisture uptake in-creases the bulk conductivity, and the moisture effects depend on phosphorus content. The bulk current thermal ctivation energy of CVD SiO. ~ (0.6 eV) is constant with varying moisture exposure. Before moisture exposure, phos-phorus-containing glass has an activation energy of 0.8 eV, and it decreases with moisture xposure. Surface conductivity is also reported as a function of relative humidity. Conductivity values are related to IC leakage currents, and it is suggested that bulk currents in PSG should not contribute to aluminum corrosion in the absence of defects, such as cracks or pinholes. SiO ~ and phosphosilicate glass (PSG) are important materials in silicon device passivation (1). Thin layers of PSG (hundreds of angstroms) have been describe