SIMULATION OF NICKEL SILICIDE GROWTH PROCESSES DURING THE FORMATION OF OHMIC CONTACTS TO SEMICONDUCTOR DEVICES
DOI:
https://doi.org/10.32782/tnv-tech.2023.2.10Keywords:
nickel, nickel silicide, temperature, modeling, non-isothermal conditions, annealingAbstract
To obtain ohmic contacts to the structures of semiconductor devices, nickel or aluminum is usually used. Unlike aluminum, nickel is well wetted by solder and allows connecting conductors by soldering, forms silicides with silicon that are stable in a wide temperature range, and allows electrolytic formation of local contacts. These advantages make it possible to apply simpler methods of assembly of semiconductor devices, to exclude metallization photolithography operations from the technological process, thus increasing the efficiency of device production and reducing their cost. Another advantage of nickel when using it to form ohmic contacts is a wide range of methods of its deposition on the surface of a semiconductor plate: electrochemical deposition of nickel; sputtering of a nickel film in a vacuum; chemical precipitation of nickel. At the same time, practically the only method of depositing an aluminum film on the surface of a semiconductor plate is the method of thermal vacuum sputtering. The article examines the mechanisms of nickel silicide formation in the process of forming an ohmic contact to silicon-based semiconductor devices and develops a mathematical model. The obtained results of the calculation of the kinetics of the non-isothermal growth of the Ni2Si silicide film indicate a significant deviation of the real annealing conditions of the nickel film from the ideal isothermal annealing. At high loading-unloading speeds of a batch of plates, the equivalent annealing time is several orders of magnitude lower compared to isothermal annealing. When reducing the speed of movement of the cassette with plates and increasing the duration of exposure of the plates in the working area, the process tends to an ideal isothermal process. The obtained results confirm that when conducting experiments to study the growth kinetics of nickel silicides, it is necessary to take into account the non-isothermal conditions of the nickel film annealing process. A nomogram has been developed that characterizes the growth kinetics of nickel silicide Ni2Si at T=673K in non-isothermal conditions. With the help of such a nomogram, knowing the experimental annealing time of the nickel film, it is possible to determine the annealing time equivalent to isothermal conditions. The nomogram can be used both during experimental studies of the annealing process of nickel metallization, and in the conditions of production of silicon semiconductor devices to adjust the annealing time of the nickel film during the formation of nickel ohmic contacts.
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