AN APPROACH TO ESTIMATE GETTERING EFFECTS IN TI-O2 REACTIVE SPUTTERING PROCESS

In reactive sputtering gettering of reactive gas at the chamber wall plays an important role in process condition changes. In this article, reactive gas mass balance and sputtering yield changes in Ti-O2 reactive sputtering have been analyzed by pressure change observation and film composition analysis to examine gettering effects quantitatively. The obtained results show the drastic change in gettering effects at the mode transition which takes place at a critical O2 partial pressure. Until the mode transition, more than 90% of the introduced O2 is consumed by gettering. The amount of gettered O2 displays a maximum just before target poisoning occurs. At this point the calculated getter pumping speed reaches about ten times larger than the physical pumping speed. After the transition, getter pumping speed ranges between 1/5-1/10 of the physical pumping speed. The sputtering yield also drops by a factor of 17 at the transition. The adsorbed/incident O2 flux ratio is found to decrease from 0.36 to 0.0010 with increasing O2 partial pressure. These results quantitatively indicate the role of gettering in condition changes.