Development and application of hardware-software complex process control electrolytic copper deposition mode with stochastic vibrations

Abstract

In this paper we describe the hardware-software system that allows the real-time support of a given voltage between the electrodes of electrochemical cell during electrolytic deposition of copper. Application of this hardware-software system enables different modes of electrodeposition: at a constant voltage, with impulse voltage and any other (including stochastic) modes of electrodeposition.

The voltage intervals, which correspond to activated and diffusion-controlled regimes of electroplating were determined on the basis of the constructed polarization curve. This curve describes the deposition of copper on a copper plate at a given concentration and temperature of the electrolyte. Stochastic electrodeposition regime was performed using Chua generator of non-linear oscillations. In this case the non-linear oscillations occur in the interval between two voltage values, which are determined from the polarization curve with a random continuous transitions between these values.

SEM study shows that grain structure morphology of the deposited copper layers varies significantly depending on the deposition mode. In stochastic voltage mode the deposited copper layer consists of monodisperse rounded grains. The lamellar and irregular grains are formed during deposition in the constant voltage mode. The size of these cristallites is much bigger than size of the cristallites formed in stochastic mode. The XRD measurements revealed that the crystallites formed in constant voltage mode are textured with preferential (220) orientation of atomic planes parallel to the sample surface. In stochastic mode we observed almost ideal polycristalline copper layer with nigligible microdistortion of the crystallites and absence of mechanical stresses.