Theoretical and experimental modelling the specific resistance of vertical ohmic contacts Au–Ti–Pd–n⁺-n-n⁺-Si in IMPATT diodes

摘要

The method of electrophysical diagnostic of n⁺-n-n⁺ structures at the etching stage of manufacturing process of power IMPATT diodes has been proposed. A numerical method for specific contacts resistance calculation of vertical ohmic contacts with a non-uniform doping level has been developed. Vertical ohmic contacts Au–Ti–Pd–n⁺-n-n⁺-Si both before and after etching were used for experimental checking this model. It has been computed the value of contact resistance in the interface metal–n⁺ with correction of contribution of n⁺-n and n-n⁺ resistances to the total resistance. The values of total effective resistances of vertical ohmic contacts Au–Ti–Pd–n⁺-n-n⁺-Si may be calculated using the Cox–Strack method. We used solutions of Laplace’s equation for computation of specific contact resistance metal–n⁺ without contribution of interfaces n⁺-n and n-n⁺. The values of specific contact resistance were ~10⁻⁶ Ohm·cm². This method allows to control the manufacture process by monitoring the changes in electrophysical properties of the structure between etching cycles.