Quantitative description of the growth kinetics and morphology of TiN thin films produced by a physical vapour deposition method

Abstract

Physical vapour deposition (PVD) methods are frequently employed techniques in surface engineering. In one implementation Of these methods, the particles that are to form the film are accelerated towards the treated surface in the form of plasma pulses (PAPVD). The accelerated particles come partly from a particle gun of a controlled chemical composition and are also provided by the gas inside the chamber. The accelerated particles hit the treated surface and subsequently recombine to form a thin film. Among others, TiN films are produced in this way, as has been shown, for example, in [1]. The kinetics of the deposition process growth is to a large extent controlled by the parameters of the plasma and the frequency of the pulses. The morphology and microstructure of these films are affected by the temperature of the process and the heat transfer rate from the treated surface. In this letter an attempt has been made to verify these general statements by the data obtained on a TiN film produced under technological conditions, which was described in [2]. The study covered the kinetics of thin film growth and its morphology. TiN films were produced by plasma pulses using the equipment described in [2]. High purity Ti electrodes were used as a Ti gun and pure nitrogen gas in the reaction chamber was a source of N atoms. Two materials were treated: copper and iron. Flat specimens were used in the form of disks. The morphology of the deposited films was studied using scanning electron microscopy (SEM) and an image analyser. Individual features of a film surface, discussed below, were described in terms of their area, A, equivalent diameter, d2 (defined as the diameter of circle of the area A), and perimeter, p [3]. The distribution functions of the measured parameters, f(A) and f(d2), were analysed and the distribution function parameters were computed, such as (i) mean values, E(A) and E(d2), (ii) standard deviations, SD(A) and SD(d2) and (iii) coefficient of variations, CV(A) and CV(d2) (coefficient of variation is defined as the ratio of the standard deviation to the mean value of a given parameter). Images characteristic of the various stages of the deposition process are shown in Fig. 1 and results of the measurements in Fig. 2. Two characteristic stages in the deposition process can be distinguished in the present study. In the early stages of the deposition, the film is deposited on a metal substrate