EFFECT OF OPERATION PARAMETERS ON THE SPUTTERING AND EMISSION PROCESSES IN RADIOFREQUENCY GLOW-DISCHARGE - A COMPARISON WITH THE DIRECT-CURRENT MODE

In this paper, a comparison of the direct current (DC) and radiofreque ncy (RF) operating modes in glow discharge optical emission spectromet ry (GD-OES) is carried out using the same discharge chamber, based on the Marcus design, powering alternatively with DC or RF energy. The ef fect of discharge pressure, the DC bias voltages and the delivered pow er divided by the DC-bias voltage on the sputtering rates, emission in tensities and emission yields achieved for conducting materials was in vestigated in order to characterize both discharge types. Our results show that the effect of plasma variables on sputtering rates and emiss ion yields using a DC-GD based on the chamber described by Marcus, can be considered to follow trends similar to those of the well-known DC- Grimm source. However, if the effect of plasma variables are compared for a DC-GD and a RF-GD, both generated by the same source as designed by Marcus, the behaviour of the DC and RF operations of the source pr oved to have some differences. Thus, at a fixed delivered power, the s puttering rate in the DC-GD decreases noticeably with pressure while t he reverse effect is observed in the RF-GD. Moreover, under selected o perating conditions, using the tin emission line (Sn I 380.102 nm), lo wer sputtering rates and higher emission yields were observed for the RF-GD than for the DC-GD source. Extension of known theoretical expres sions and concepts from analytical DC-GD to RF-GD-OES work appears rat her involved and is not yet possible. (C) 1998 Elsevier Science B.V. A ll rights reserved.