An inductively coupled GEC Reference Cell has been modified to allow etching of oxide wafers under conditions typical of commercial high density plasma reactors. This study reports on the oxide and photoresist etch characteristics as a function of reactor source power, bias power and pressure. Diode laser absorption spectroscopy (DLAS), OES and Langmuir probe measurements were made at the same time. DLAS has shown that C@sub 4@F@sub 8@ is largely dissociated to form C@sub 2@F@sub 4@, CF@sub 2@ and CF in the discharge. Over an oxide surface, CF@sub 2@ and CF are consumed in the oxide etch process, but only when the bias power is sufficient to keep the oxide surface clean through energetic ion bombardment. Langmuir probe measurement of the ion current density was used to estimate the bias voltage at the wafer at which this transition took place. For C@sub 4@F@sub 8@, this transition occurs at ~ 60 eV (75 W bias power) in the GEC Cell. At higher bias powers (125 W) where oxide etching is fast (~600 nm/min.), CF@sub 2@ appears to be the key radical for the etch process since ~50 percent (2.7-3.0 mTorr in a 15 mTorr C@sub 4@F@sub 8@ discharge) is consumed. These values were obtained by comparing the CF@sub 2@ concentrations over non-reactive wafer surfaces versus blanket oxide wafer surfaces undergoing etching. CF is shown to display a similar trend, but its concentration is an order of magnitude less than CF@sub 2@, and consequently cannot account on a mass basis for the amount of reactants necessary to balance the amount of etch products. Over a PR surface, neither CF@sub 2@ nor CF concentrations vary as a function of PR etch rate. Consequently, they do not appear to be involved in the PR etch mechanism. However, PR etching is also critically dependent on bias power. PR films etch presumably due to energetic ion bombardment that degrades the PR film, making it liable to attack by fluorine. This project was funded by SEMATECH and NSF