Correlation between the diffusive and electrical barrier properties of the interface in polysilicon contacted n+-p junctions

The diffusion of As from polysilicon into boron-implanted single-crystal silicon through different interfaces obtained with different surface preparation techniques prior to polysilicon deposition is studied. The impurity profiles have been analyzed by SIMS and measurements and ESCA has been used to determine the structural properties of the interface. Electrical measurements on diodes have been performed to study the diode characteristics and the electrical interface resistance. The diffusion through chemically grown oxide layers is found to be strongly retarded with respect to "oxygen-free" interfaces. A strong correlation appears to exist between the diffusive and electrical barrier properties of such interfaces. For increasing oxygen content at the interface, the minimum diffusion cycle required to obtain good diode ideality factors is higher as is the electrical interface resistance. We have observed an order of magnitude increase in the contact resistance for annealing temperatures between 800° and 900°C. One of the major conclusions is that the necessity to go to higher temperatures to decrease the series resistance of the polysilicon contacts in the case of chemically grown interface oxides is compromising their use in high-performance VLSI technologies.