THE INFLUENCE OF MAGNETRON CONFIGURATION ON ION CURRENT-DENSITY AND DEPOSITION RATE IN A DUAL UNBALANCED MAGNETRON SPUTTERING SYSTEM

A series of experiments were carried out to investigate the influence of magnetron configuration on the performance of a dual unbalanced mag netron system. The rig was operated in the closed-field (CF), mirrored -field (MF) and, for comparison, single unbalanced magnetron (UBMS) co nfigurations. The performance of the rig was assessed in terms of the substrate ion current density, I-s, deposition rate, R, and the ion-to -atom ratio incident at the substrate, J(i)/J(a). R was not significan tly influenced by magnetron configuration. Also, for all configuration s, R decreased with increasing substrate-to-target separation, d(s-c), in a relationship of the form R=a(d(s-t))(b), where b approximate to- 2. I-s also decreased with increasing d(s-t). However, I-s values were 2-3 times lower, and the rate of decrease of I-s with increasing d(s- t) was greater, when operating in the MF, or UBMS mode, compared to th e CF mode. Values of b in the relationship I-s=a(d(s-t))(b) were -0.26 , -0.53 and -0.59 for the CF, UBMS and MF modes, respectively. An impo rtant finding of this study is that, although both deposition rate and ion current density decrease with increasing separation, because the rate of change with separation is different in each case, the ion-to-a tom ratio actually increases with increasing separation. For example, operating in the CF mode, J(i)/J(a) was found to increase from 1.35 to 3.0 when d(s-t) was increased from 80 to 150 mm. (C) 1998 Elsevier Sc ience S.A. All rights reserved.