STUDY OF THE INFLUENCE OF TECHNOLOGICAL FACTORS ON THE PARAMETERS OF DIODES WITH NICKEL CONTACT

Abstract

Along with aluminum, nickel is used for the metallization of silicon diodes. Unlike aluminum, nickel is well wetted by solder and allows conductors to be connected by soldering, forms silicides with silicon that are stable over a wide temperature range, and allows electrolytic formation of local contacts. These advantages make it possible to use simpler methods of assembly of diodes, to exclude metallization photolithography operations from the technological process and, thus, to increase the efficiency of device production and reduce their cost price. But, as practice has shown, the use of nickel to create ohmic contacts is associated with its negative effect on the reverse branch of the diode’s current-voltage characteristic. The negative effect of nickel on the parameters of diodes is especially intense in the presence of structural defects in silicon. It was established that the reason for the degradation of the reverse branch of the current-voltage characteristic of a diode with a nickel ohmic contact is the oxidation defects of the packaging, which are formed in silicon during the technological operation "Thermal oxidation". In order to prevent the formation of structural defects in silicon, it was necessary to choose an effective heterization method. Since oxidation packing defects are formed in silicon, starting with the first high-temperature operation – thermal oxidation of the plates, it is obvious that heterization should be used at the very beginning of the diode manufacturing process. The conducted studies showed that the most effective method of preventing the formation of structural defects in epitaxial layers is the creation of a heterogenous region on the reverse side of the substrate by means of phosphorus diffusion into it at a temperature of 1100°C for 60 minutes before the technological operation "Thermal oxidation". The experimental results of the study of the influence on the inverse characteristic of the varicap of the heterogeneity process are given, and the possible mechanisms of this influence are also analyzed. The effectiveness of the proposed technology with the use of hetering in reducing the level of reverse currents and increasing the output of suitable devices is shown.