Mid frequency sputtering with TwinMag® -: a survey of recent results

Since DC magnetron sputtering was introduced for the manufacturing of optical thin film systems on large area glass substrates, coating processes have suffered from poor long term stability and low deposition rates. After long years of intensive development work, today AC (midfrequency) powered twin magnetron arrangements are capable to overcome these drawbacks. During the past two years much data has been collected on AC reactive deposition of SiO2, Si3N4, Ta2O5, TiO2, SnO2, and ZnO. SiO2 and TiO, the most prominent candidates for optical interference coatings, can be deposited on large scale at rates exceeding 5 nm/s in a stable continuous process for more than 300 hours. The deposition rates for SnO2 and ZnO are in the range of 10 nm/s. High density, low surface roughness and very good optical properties of all deposited materials result from bombardment of the growing film by a high flux of energetic ions. The paper gives a survey on recent results with special emphasis on TiO2 and SnO2 layers. New applications like antire-flective-antistatic coatings are presented. Enhanced performance and high resistance against environmental attacks indicate that AC sputtering will play a major part in the future of PVD technology. (C) 1998 Elsevier Science Ltd. All rights reserved.