Invited Paper PS2-ThM3
Noninvasive Monitoring of Ion Current and Ion Energy during Plasma Processing

Thursday, October 18, 2007, 8:40 am, Room 607

The bombardment of substrate surfaces by energetic ions plays an important role in plasma etching and other plasma processing applications. To obtain optimal results, ion current and ion kinetic energy must be carefully controlled. Unfortunately, directly measuring ion current or energy in situ, at a wafer surface during plasma processing, is difficult or impossible. To solve this problem, a technique for indirectly monitoring ion current and energy has been developed. It relies on measurements of the waveforms of rf current and voltage applied to the wafer electrode, which are interpreted by fundamental physical models of the plasma and its sheaths. The technique is noninvasive, i.e., there is no need to insert any probe into the plasma reactor, and it is suitable for use during actual processing in industrial equipment. This talk will describe the technique, the models it uses, and validation tests performed in an rf-biased, inductively coupled plasma reactor. It will also present results from experiments that demonstate the use of the technique to monitor ion current and ion energy during fluorocarbon etch processes and argon sputtering processes, including processes that were perturbed by reactor drift and equipment "faults." I will also discuss the present limitations of the technique and potential extensions of the technique to make it applicable to other plasma processes and other types of plasma reactors.