Study of gas phase, surface phase chemistries and plasma-surface interactions in fluorocarbon plasmas in an inductively coupled modified gaseous electronics conference (mGEC) reactor

The gas phase, surface phase chemistries and plasma-surface interactions were studied in CF4 plasma in an inductively coupled modified gaseous electronics conference (mGEC) reactor. The investigation of the gas and surface chemistries has shown that the plasma chemistry is affected by discharge conditions including the flow rate of the feedgas, pressure, RF source power, RF bias power and the gap between the RF coil and the chuck. The fluorocarbon radical density was found to be much higher during the plasma etching of Si substrate than during plasma deposition. The thickness of the thin, protective fluorocarbon film on Si substrate during plasma etching is largely determined by fluorocarbon radical densities, atomic fluorine density, and the ion energy.;The study of the effect of wall temperature on the gas phase chemistry and substrate reactions with initially clean and seasoned walls indicates that the films formed during the seasoning step can be involved in surface production of fluorocarbon species upon wall temperature increase. In other words, a seasoning step may not be enough to ensure stable gas phase chemistry and substrate reactions unless the wall temperature is also controlled. The temperature dependence of the fluorocarbon film deposition on the substrate has shown that the low-energy ions from the plasma play a very important role in the fluorocarbon film deposition and removal. Ion-assisted incorporation, direct ion incorporation and ion-assisted desorption are considered as the three major ion initiated processes determining the overall film formation and destruction. Ion-assisted incorporation and desorption are surface-temperature-dependent and important only at low and high temperatures respectively, while direct ion incorporation is independent of the surface temperature. The substrate material can also affect the deposition rate and composition of the fluorocarbon film. Finally, the examination of the oxygen plasma cleaning indicates that the cleaning step is not complete in many cases, and the residual film may have effect on the film growth in subsequent processing.