Semion System Retarding Field Ion Energy Analyzer Importance

Importance of ion energy distribution (IED) measurements • • • Wafer processing controlled by

RFEA Schematic Plasma + Filter 60 V G 1 G 2 Filter 0 to

Nickel Grid Structure • Electron microscope image of a nickel grid

IV Curve and Calculated IED • • Average ion energy Ion flux

Design considerations • Orifice diameter < Debye length λD e. g. Te=3 e. V,

Installation • Located at any location inside a plasma reactor • Floating, RF bias,

IED • Shape of IED determined by sheath potential, ion transit time and period

IED For rf modulated sheath: • Ion transit time = Plasma + Aperture Filter

Results DC Sheath Pressure Computer Generator Match Plasma Reactor Semion Electronics

Results RF Sheath Bias Computer Generator Match Plasma Reactor Semion Electronics

Results RF Sheath Frequency Computer Generator Match Plasma Reactor Semion Electronics

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Semion System “ Retarding Field Ion Energy Analyzer

Importance of ion energy distribution (IED) measurements • • • Wafer processing controlled by energy and flux of bombarding ions e. g. etch rate, etched feature quality Ion energy measurement critical for process development Wafer usually processed using RF excitation typically, 2 60 MHz Difficult conditions in which to measure IED electrical filtering, high temperatures, sensor etched or coated during processing RFEA sensor for IED measurements developed, easily incorporated into existing reactors, compatible with majority of substrate bias conditions

RFEA Schematic Plasma + Filter 60 V G 1 G 2 Filter 0 to +V G 3 Filter 70 V 60 V G 4 I Filter C Insulator Aperture

Nickel Grid Structure • Electron microscope image of a nickel grid

IV Curve and Calculated IED • • Average ion energy Ion flux

Design considerations • Orifice diameter < Debye length λD e. g. Te=3 e. V, Ne=1017 m-3 …… λD~40µm • Ion transit length < Ion mean free path λi • RFEA depth 0. 6 mm ~ 100 m. Torr in Argon

Installation • Located at any location inside a plasma reactor • Floating, RF bias, grounded • Connected through a vaccum port via ceramic beaded cable Computer Generator Match Plasma Reactor Semion Electronics

Installation

IED • Shape of IED determined by sheath potential, ion transit time and period of sheath potential waveform. For DC sheath, <E>~<Vs>, E~0 Plasma + Aperture Filter 60 V G 1 G 2 Filter 0 to +V G 3 Filter 70 V 60 V G 4 I Filter C Insulator •

IED For rf modulated sheath: • Ion transit time = Plasma + Aperture Filter 60 V G 1 G 2 Filter 0 to +V G 3 Filter 70 V 60 V G 4 I Filter C Insulator •

IED Shape

Results DC Sheath Pressure Computer Generator Match Plasma Reactor Semion Electronics

Results RF Sheath Bias Computer Generator Match Plasma Reactor Semion Electronics

Results RF Sheath Frequency Computer Generator Match Plasma Reactor Semion Electronics

Spatial Uniformity