11/8/ Diagnostic and Etching Studies of Inductively Coupled Plasmas SFR Workshop November 8, 2000 Matthew Radtke, John Coburn, David Graves Berkeley, CA 2001 GOAL: Detection of depositing etch product in Si-O-Cl system by 9/30/2001.

11/8/ Motivation Increasingly stringent processing demands require better fundamental understanding of gas phase chemistry and plasma-surface interactions. Plasma diagnostic and surface interaction measurements are used to understand plasmas and provide modeling data. CF 4 is a common processing plasma and the radical recombination chemistry is not well understood.

11/8/ Experimental Apparatus – side view

11/8/ Experimental Apparatus – top view Langmuir Probe Ion Analysis Quadrupole Mass Spectrometer Neutral Analysis Quadrupole Mass Spectrometer Quartz Crystal Microbalance Plasma Chamber Optical Emission pressure gauge * industrial processing plasma use optical emission * very few systems have attempted to make all measurements simultaneously chopper beam background Thermocouple

11/8/ Experimental Procedure Measured QuantityMeasurement Diagnostic pressurepressure gauge radical and neutral densitiesquadrupole mass spectrometer (appearance potential mass spectrometry) ion compositionquadrupole mass spectrometer electron densityLangmuir probe electron energy distribution (electron temperature) Langmuir probe plasma potentialLangmuir probe average neutral temperatureoptical emission wall temperaturethermocouple * mass spectrometer measurements are at wall * Langmuir probe can measure profile

11/8/ Quartz Crystal Microbalance Quartz Crystal Microbalance (QCM) –films deposited on microbalance crystal –crystal oscillates at characteristic frequency proportional to its mass –change in mass causes frequency change oscillator crystal film plasma

11/8/ CF 3 Recombination Coefficient F in (CF 4 ) F out (CF 4 ) CF 4 CF 3 plasma Assume CF 4 formation at walls is due entirely to CF 3 recombination CF 4 balance in – out + recombination = reaction CF 4 + e  CF 3, CF 2, CF 3 +, … Walls – fluorocarbon deposited on stainless steel (30 +/- 2 o C) QCM - negligible deposition rate APMS - radical and neutral densities Langmuir Probe - electron energy distribution (f o )

11/8/ K diss calculation P(mTorr)k diss (10 -8 cm 3 /s) = 0.038

11/8/ Result Milestones Studies of plasma-wall interactions (e.g. Si/O/Cl for gate/trench etch) Studies of high-K etching (e.g. etch precursors, by-products, selectivity) Studies of plasma surface interaction (e.g. N 2 plasma / PET; NF 3 plasma / elastomer)