Effect of Passivating Coatings on Metallization Topology in Production of Semiconductor Devices

Abstract

The surface quality of the metallized contact pads on the crystal plays an important role in the production of semiconductor devices. This paper presents experimental studies of the effect of a protective passivation film of silicon oxide on the surface structure of aluminum metallization in the field of forming contact pads. Plasma chemical deposition of passivation layer SiO2 from gas phase (PECVD method) was carried out on prepared samples of silicon with aluminum metallization using a high-frequency power source with a frequency of 13.56 MHz. After that, chemical etching of precipitated silicon oxide was carried out to simulate the process of forming contact areas of semiconductor device crystals. The resistance of the metallization surface to plasma processes was studied by raster electron microscopy. It is shown that as a result of the process cycle, defects of the dislocation type are generated in the applied film Al. The nature of the observed defects has been found to be different. The revealed large square-shaped pits with a size of ~ 1 μm at the places where dislocations come to the surface are of a single nature and appear independently of the processes of applying passivation coatings, which is determined by the orienting action of a single-crystal substrate having some low dislocation density. While the second type of defects, shown by the presence of etching pits measuring ~ 100-300 nm, is characterized by a higher surface density. Moreover, the exclusion of the passivation process with silicon oxide did not lead to the appearance of this type of defects, which determined their nature associated with the ion bombardment of the Al layer during the plasma chemical deposition of silicon oxide from the gas phase. It is also shown that a feature of this type of defects is their disorientation both with respect to the first type of defects and with respect to each other. Detection of the structure of the metallization layers was carried out by X-ray diffraction, the results of which show the polycrystallinity of the formed aluminum metallization. The preferred orientation of the aluminum film corresponds to the substrate Si (111).