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Ion Sampling From RF Discharges at the Cathode

IP.com Disclosure Number: IPCOM000089070D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Viswanathan, NS: AUTHOR

Abstract

In reactive ion etching diagnostics it is necessary to sample ions which are near to the cathode surface since the etch reactions are usually carried out at the cathode. The ions (and also possibly fast neutrals which are formed by electron detachment processes) reach the cathode surface with fairly large energies of typically 1-2 KV depending on the reaction conditions. A method is provided for obtaining energy deceleration of particles from the discharge plasma which is suitable for use with a simple quadrapole mass spectrometer.

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Ion Sampling From RF Discharges at the Cathode

In reactive ion etching diagnostics it is necessary to sample ions which are near to the cathode surface since the etch reactions are usually carried out at the cathode. The ions (and also possibly fast neutrals which are formed by electron detachment processes) reach the cathode surface with fairly large energies of typically 1-2 KV depending on the reaction conditions. A method is provided for obtaining energy deceleration of particles from the discharge plasma which is suitable for use with a simple quadrapole mass spectrometer.

Ions 1 from RF diode plasma reactor 2 reaching the surface of cathode 3 are passed through exponential ion filter 4 to quadrapole mass spectrometer 5. These filters are described by M.L. Vestal et al in Rev. Sci. Instruments 47, 15 (1976). The filter operates at a deceleration rate of 7 X 10/-4/, which translates to a useable exit voltage of about 0.2 volt in the low range. The choice of suitable voltage dividers permits the choice of the exit entrance voltage ratios so that the ion energy spectrum can be synthesized.

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