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larity in the Kinetics and Mechanisms of Galvanostatic Anodic Oxidation of Silicon, Silicon Carbide, and Nitride L. P. Mileshko*, ** Southern Federal University, Rostov-on-Don, 344006 Russia *e-mail: [email protected] **e-mail: [email protected] Received September 13, 2018; revised October 16, 2018; accepted November 20, 2018

Abstract—It is shown that the formation of anodic oxides in the galvanostatic mode of electrolytic anodizing of Si, SiC, and Si3N4 proceeds with the activation control of the process. It is suggested that the limiting stage of the oxidation process of these materials is the anodic reaction of the formation of intermediate monoxide SiO. Keywords: anodic oxidation, anodic oxide films, silicon anodizing, silicon carbide anodizing, silicon nitride anodizing DOI: 10.3103/S1068375520040109

INTRODUCTION The electronics of anodic oxide films of silicon and its compounds formed in alloying electrolytes is at present an important research area, which could successfully develop in the future [1]. It is shown in works [2, 3] that phosphate and borate anodic oxide films (AOFs) are promising diffusants for microelectronic technology. However, the electrochemistry of alloyed AOFs (AAOFs) is understudied [4]. Up until now there has not been any basic theory that describes the physicochemical mechanism of the input of an alloying impurity admixture into the composition of the semiconductor oxide film in the course of electrolytic anodizing. As was shown in [5, 6], the rate of increase of the forming voltage U at the galvanostatic oxidation of silicon carbide on the sections of the AOF linear growth depends on the current density j according to the following exponential law:

dU = αj β, (1) dt where t is time, α and β are the approximation coefficients; in this case, the Gunterschulze and Betz exponential law for the ionic component of the anodic current density j+ is true [7, 8]: (2) j+ = A exp(BE ). Here, E is the electric field intensity in the AOF; A and B are the constants. The facts of alloying of anodic silicon dioxide films by phosphorus and boron were earlier confirmed in [1,

9] with the help of the Auger electron spectroscopy method. The experimental dependences dU/dt on the current density j obtained in [9] are reasonably approximated by expression (1). Following [10], we estimated the rate of the oxide layer formation in the course of the galvanostatic anodizing of silicon according to the value of the kinetic parameter U j (U denotes time differentiation of voltage) characterizing the voltage increase rate on the linear sections of the current–voltage characteristics of the oxidation process. It is shown in [11] that the experimental dependences of the formation rate of the alloyed AOFs on the current density are straightened in the semilog coordinates, and they are well approximated at different stages of the process by the dependences of the following form: U = μ + ν ln  j  , (3) j  j  0 where μ and ν are the coefficients and j0 is the normalizing parameter with the dimensionalit