PARTICLE CONTAMINATION CHARACTERIZATION IN A HELICON PLASMA-ETCHING TOOL

There is much current interest regarding the formation, transport, cha rging, and behavior of particulate contamination in high density plasm a tools, as these tools are generally regarded as the future of plasma processing for the semiconductor industry due to the need to obtain g reater anisotropy and faster process rates concurrently with reduced s urface damage. Because of the low pressures in which these tools typic ally operate (<5 mTorr), the likelihood of homogeneous nucleation proc esses leading to particle contamination problems is low. Similarly, th e effect of ion drag is also expected to be greater, possibly leading to reduced particle trapping effects. Yet, few laser light scatter stu dies have been performed in high density plasma tools. This study is t he first in situ characterization of particle contamination ina plasma etching tool using a helicon source. It was performed during normal p rocess conditions for poly-Si etching and also under intentionally alt ered process conditions designed to produce particles. The effect of a bipolar, electrostatic chuck on wafer particle deposition was also in vestigated. Results showed that under normal process conditions, few p articles were deposited onto the wafer; those that were observed were attributed to thermal stress effects resulting in flaking of depositio n films, probably on the quartz bell jar of the source. Results also s uggest that the electrostatic chuck increased particle deposition when the clamping voltage was applied. No trapping was observed over the w afer or near the source. However, some trapped particles were observed below the wafer platform. These particles showed unusual motion, but probably have minimal effect on wafer contamination. The issues pertai ning to particle contamination formation and transport in this high de nsity plasma tool are discussed. (C) 1996 American Vacuum Society.